It is assumed that you will prevent sheep totally destroying young trees, or eating the bark of older trees.
Grass under fruit trees
Grass competes with your fruit trees for soil nutrients and for water. The most critical issue is water. Some fruit and nut trees are deep rooted and can withstand drying out better than others.
Relatively grass tolerant fruit and nut trees
Walnuts, macadamias and pecans can 'more or less' look after themselves in a dry year (except in prolonged droughts on sandy or stony dry soils and with deep watertables). Some fruit trees tolerate grass competition for water until summer really sets in, and then they can suffer in a dry year. These are stonefruit such as plums, peaches, and apricots. They fruit relatively early, and with luck, fruit are fully formed by time of water deficit. I am not suggesting that you can ignore the need to avoid water stress in stone fruit trees - but arguing that that in most years, early and mid season stonefruit varieties on soils with an average water holding capacity will tolerate grass to the trunk and still give the home fruit grower an average crop. Late season peaches and plums should ideally be mulched, or have the vegetation sprayed out before the soil loses much of its retained water with the onset of drier conditions around late spring/summer.
Relatively grass intolerant fruit and nut trees
Shallow rooted fruit trees, specifically citrus, casimiroas, apples on malling 9 dwarf rootstock - and to a lesser extent persimmons and feijoas - suffer badly if the surface soil dries out to any great degree. Casimiroas, in particular, will shed large numbers of set fruit if they are 'checked' by dry soil. Hazel nuts must have relatively moist soil in the growing season. You can let the grass grow to the trunk of these trees in the winter, but the sward must be sprayed out relatively early - probably by late spring at the latest, if soil moisture is to be conserved. If it is a wet spring then it can be delayed, but spring grass growth is so strong that any dry spell thereafter will quickly deplete the soil of its moisture reserves.
If you are lucky enough to have a bore and plenty of water available over summer, then you can use it in late spring when needed to extend the period before you need to spray under your trees.
Larger home orchards on 'lifestyle blocks' most often have the home orchard planted into existing pasture of perennial ryegrass and clover. This pasture responds well to both grazing and mowing, and is thus the pasture of choice for most stonefruit and apple orchardists. While white clover is very shallow rooted and tends to 'burn out' in summer, perennial ryegrass is more persistant. In a dry year, even the ryegrass will die back, as it is not especially deep rooted. In addition, it can be badly affected by both grass grub and stem weevils.
Ryegrass resists insect attack if
it hosts a fungus in its tissues which produces a substance which
insect feeding. The chemicals produced by these 'endophyte' fungi
a toxic reaction in grazing animals ('ryegrass staggers').
Ryegrass without this
summer, sheep will spend 5
times longer grazing clover (where it is available) than ryegrass
endophyte free or not). Their proportional preference has been
at 70% clover and 30% ryegrass, at least in summer. In the
conditions of spring and autumn seasons more mature strawy grasses
be preferred. A good ryegrass and clover sward would hope to
levels of 30%.
It is not easy to maintain a high clover concentration
the sward over time, although specialist summer clovers such as
are changing this. The downsides of a ryegrasss/white clover sward
the summer endophyte problem in ryegrass, and the loss of feed
clover dies right back in a hot summer. Summer clover loss also
the soil surface to even further drying out, and the open patches
be colonised by weeds when moisture returns.
Increasingly common - and hard to get rid of if you don't want it - kikuyu has been introduced to the warm temperate zone from Africa to help step-through the lack of feed in summer (as was paspalum grass). Kikuyu is an irritation in the home orchard as it spreads by underground rhizomes and pops up where it is not wanted. In good conditions, it grows very fast, and its spreading and semi-rambling habit allows it to get into the lower braches of bushy trees, making eradication difficult (a herbicide that affects grass species only is the best recourse - but can't be used on sensitive fruits, such as peaches and other stone fruit).
Kikuyu is a highly nutritious feed (70% or more digestibility) in
good conditions and under good
management, and it certainly does the job
summer, providing feed when there is little else. It also gives
soil surface cover in summer, helping to slow drying out. But it
clover when it is growing strongly, and worst of all, nearly
in winter frosts. A kikuyu
sward without clover or other grasses that was green in late
be almost totally brown in mid winter.
Intensive and timely grazing and mowing in summer and autumn can allow clover to hold its own and be available for winter feed. As long as there are sufficient mouths to closely control the kikuyu in autumn, summer dormant/winter active subterranean clover might be the key legume for this pasture. Kikuyu swards winter productivity can be boosted by very close mowing in autumn (preferably almost 'scalping' it so some bare earth shows) and oversowing with winter-active annual ryegrass. Ideally, at least a third of the sward would be legumes and winter active grasses.
But even a pure stand of kikuyu has its uses - in the right
It can be a very useful summer 'lifesaver' if it is isolated to a
area, such as an open woodlot.
This is a euphemistic term for swards between rows of trees that have been sprayed out of kikuyu or other vegetation, then left for various grasses and herbaceous annuals and perennials to regenerate. Just what appears depends on the seeds dormant in the local soils, the species present in adjacent wastelands, and whether any attempt was made to sow clover and perennial rye, or any other grass legume mix. The ultimate composition is also influenced by whether or not the sward is allowed to reseed, as some of these 'wild' grasses are annuals. Swards that are cut or grazed fairly often, and that are always cut in late spring, tend to favor low growing grasses. Those cut or grazed infrequently, and never in late spring, can favor taller grasses.
Improving mixed swards
Simply applying fertiliser will change species composition and percentages - for the better. Fertiliser applied to low fertility areas favors the more fertiliser-responsive species initially present in low numbers to increase at the expense of less responsive annual grasses. Simply applying superphosphate and lime can double the percentage of clovers in the sward. Adequate fertiliser applications can shift species composition from low fertility annual species such as hair grass (Vulpia dertonensis) and shivery grass (Briza minor) to more responsive perennial species such as sweet vernal, soft brome, kentucky bluegrass (Poa pratensis) and perennial ryegrass (a few wild species such as Microlaena stipoides, a shade-adapted, drought hardy creeping perennial, are genuinely useful and fertiliser responsive). The greatest shift occurs with both increased fertiliser and careful grazing to allow light into the base of the sward. This encourages 'tillering' (budding of leafy - and therefore nutritious - side shoots from the base of the plant) in fertiliser responsive grasses. It also increases clover growth.
Even the simple intervention of a single application of 685 kgs of superphosphate per acre (about 1.5 tonnes per hectare), followed by oversowing white clover has been shown to bring a very large jump in pasture yeild in the year after application, and the large improvement (sometimes pasture dry matter yeild can even double) persists for at least 6 years.
Highly productive ryegrass-clover based commercial pastures need to be re-sown every 7 or so years to keep ryegrass the dominant species. As sheep are a by-product of home orcharding, such strenuous efforts are not required. It may be better to concentrate on developing a legume and grass based sward that is permanent and able to provide reasonable grazing in most winters and most summers. Keeping the flock small enough to allow areas to be 'locked up' and left to re-seed naturally may be an important strategy for long term easy sustainability. Short-lived herbs, such as the biennial chicory, either have to be regularly oversown, or, less effectively, left to reseed naturally from ungrazed waste areas into adjacent grazing strips.
As home orchard soils are usually well fertilised, fertiliser responsive and winter active fescues, and perhaps cocksfoot, may be more strategically useful than ryegrass. In one trial, lambs fed exclusively tall fescue and clover pasture from birth to sale grew at a much faster rate than those fed the traditional ryegrass and clover. This reason isn't known - perhaps it reflects the deep rooting, summer productiveness of tall fescue, giving more, younger, leaves than ryegrass, with more metabolizable energy and better protein content. All of which results in the lambs obtaining higher quality per summer bite relative to ryegrass.
The key elements to improving a mixed sward are:
In broad terms, the aim is to keep shifting the species composition until there is a good mix of species meeting several objectives. There needs to be a good proportion of deep-rooting and drought-resisting grasses and herbs able to access moisture from the lower layers of the soil, and thus supply food when the winter active grasses and more shallow rooted legumes dry up in a drought. There need to be humus-building species to enhance soil moisture retention and growth - deeply rooted species that break up soil pans, provide a channel to quickly move moisture deeper into the soil, and that provide large quantities of fine roots that build soil organic matter as they die and rot deep within the soil. There need to be a mix of grasses, legumes and herbs of such nature that tend to support sheep health by minimising the risk of bloat, provide high concentrations of protein year round to repair gut damage from worms, supply condensed tannins to aid worm resistance and resilience, and capture and concentrate some important microelements such as selenium. Of course, the cultivars selected should be highly productive through increased disease resistance and genetically increased growth potential.
Access to irrigation for fruit trees
sward management strategy
If the strategy as a home fruit grower of citrus (or other surface rooted fruit tree) is to encourage tall grasses such as tall fescue and soft brome in order to get the greatest amount of mulch (and greatest amount of soil building fine roots), then the grass can be left uncut until it reaches full height near seed maturity in late spring/early summer. In the interim, the sprayed-out bare soil under the citrus will need to be irrigated. Once the grass is cut and pitch-forked onto the irrigated citrus, little re-growth is likely until late summer rains. Re-growth between the rows can be expected in earnest from autumn on, and as the main citrus season is winter, controlled sheep grazing at this time fits in nicely. The sheep would have to be kept out of the citrus/feijoa/casimiroa rows from spring onward to allow the tall grasses to grow to full height, but grass is usually abundant at this time anyway.
Under this regime, taller legumes are needed - lotus or perhaps
sulla. Some of the taller ladino white clover cultivars might also
able to persist.
But, if no irrigation is available, it is very unwise to leave the citrus trees unmulched until summer. Most of the early seeding annual and perennial grasses, such as Briza minor (shivery grass, an annual, ~20 cm), Poa annua, and a little later, the perennial Anthoxanthum oderatum (sweet vernal) produce too little bulk to warrant leaving to mature. In the absence of irrigation, and on very free draining sandy or volcanic soils, other mulching material has to be found. In this case, the land between the rows might be planted in a drought resistant grass, such as tall fescue. This can be cut in mid spring before it is fully mature and while the soil is still moist. If the fescue has been well fertilised it should grow back strongly, and can then be grazed into early summer. If the summer is shaping up to be dry, the fescue can be kept to about 3 cms, reducing competition with the orchard trees.
Fitting sward choice to breeding sheep for
for the home freezer
If you want to grow a few lambs, there are several critical times of year when there has to be plenty of nutritious feed available. Nutritious feed has a good protein content. Protein and sugars help ewes ovulate, form ample milk, and lambs grow well as a result.
Lambs in the womb do most of their growing in the winter months, so it is very important to have strong winter growing grass species - unless you have bought in good quality hay or (expensive) supplements.
Broadly, pasture is most nutritious in the lush leafy developing seed head stage prior to seed head maturity and 'strawing' of the stem. Overall, most grass species when young and immature are quoted by authorities as having a 'dry matter' content (i.e. non-water) of around 20%- 23%, which, they say, after taking into account the relatively indigestible parts, for nearly all common grass species typically yeilds 11 megajoules of metabolisable energy for every kilogram of dry matter consumed. Thus, from an energy standpoint, the species of grass you choose will be pretty much on a par with any other when grass is abundant and starting to seed in spring and early summer.
Given values of 11 mJ per kilogram of dry matter, it is easy to calculate that a kilo of fresh cut young grass must have - very approximately - 2-3 mJ of metabolisable energy. A ewe is said to need about 8 to 10 mejajoules of metabolisable energy a day to maintain weight (larger animals need more, smaller animals need less). This translates to a daily requirement, depending on grass quality and ewe size, of from about 2.5kg to 5kgs of fresh grass per ewe per day to maintain bodyweight.
While the daily energy needs of the breeding ewe to maintain bodyweight is relatively low over summer, extra energy is needed in late summer/autumn to lay in fat for good ovulation. About 1.8 kgs of dry matter a day per 60kg breeding ewe is quoted by experts as needed to 'flush' the ewes in the period immediately before mating. As lush immature grass has, conservatively, 20% dry matter content, 7.2 kgs of fresh green sward a day would be needed by each ewe at this time. This seems absurdly high, as some trials show 56 kg dry ewes ad lib feeding on ryegrass and/or clover pasture of their choice ate only 1.36 kg fresh pasture a day! This quantity took about 5 hours to consume. On this basis, the ewes would need to feed 24 hours a day (at their observed intake rate of 5 grams fresh weight sward a minute) to be able to force down 7.2 kgs of fresh pasture! This real-life observation also throws into doubt the calculation that, 'theoretically', a ewe needs to eat 2.5kg to 5kgs of fresh grass per ewe per day to maintain bodyweight. From the data mentioned above, even in conditions of ample feed supply in front of them, they would need to graze for about 10 hours per day.
On the basis of the 'real life' observations, realistically, maintenance is more likely to be about 1.kg to 1.5kg of fresh high quality pasture per day, depending on ewe size. Obviously, poorer quality pasture will require a higher feed intake.
While interesting, these theoretical considerations have little practical meaning for the home fruit orchardist. Sward height and 'lushness' is the only meaningful measure, and can be quickly assessed by eye.
The best rule of thumb is that you can feed from any pasture
down to a
height above soil level (ignoring
around dung deposits) of about 3 cms for short
pastures based on kikuyu, Poa
and ryegrass. You can graze
to about 5 cms in tall fescue, phalaris, and prairie grass
grass swards (so long as fertility is good). The taller the grass
with, the longer time before the sheep reach the minimum
height of uncontaminated pasture. The sheep must be shifted when
uncontaminated part of the sward in the enclosure has
eaten down to the minimum advisable residual height. It could, of
be further eaten down, but this compromises grass vitality for
These 'residuals' allow the sward to 'rebound' relatively quickly,
should be regarded as minimum levels
At the point where even dung patches have been eaten close, and
only about 2cm sward height remains, the sheep do not
enough to eat, and will start to get thin.
In times of shortage,
sometimes have to be grazed harder than is strictly good for them.
short grass swards, the sheep can be kept moving onto swards of
3 cms height and off again at 2 cms, which will usually maintain
weight, but usually will not allow the ewes to lay on storage fat.
level, they would eat more if they had more to eat. Grazing long
swards, such as tall fescue or cocksfoot, down to this level would
most undesirable, as recovery would take a long time, and some
may not recover at all.
Even fast growing rye/clover pastures taken down to 2 cms will
6 weeks or more (depending on moisture, heat, and soil fertility)
recover to a level where they can be once more re-grazed to 3 cms
For flushing the ewes in autumn, the pasture needs to be high quality and abundant enough to sustain the removal of at least double the 'weight maintenance only' level (i.e.the pasture needs to start off at 5 cms high at least for short grasses, and at least 7 cms high for tall grasses). Quality can be boosted with specialist feeds. Additional high protein feed from certain legumes (for example, sulla and birdsfoot trefoil) grazed in the ten days immediately before mating has a different physiological pathway to feeding more metabolisable energy in good grass, or metabolising the proteins in clover in the rumen. The result, however, is similar to flushing on grass. Feeding these legumes boosts ovulation and retention of embryos, and thus results in more lambs (an increase of about 5-10%). However, birdsfoot trefoil is not really persistent in a sward, and sulla is a fairly large plant. Both might have to be grown separately.
A little better than maintenance is all that is required in earlier
stages of pregnancy.
But in the last
month of pregnancy a similar amount of feed to flushing (about 2
kg to 3 kg of fresh high quality pasture per day) is needed to
large healthy lambs that will survive. Again, smaller ewes have
requirements than this. Where mating is controlled, it
be timed (gestation is about 5 months in sheep) so that birthing
with the first month of spring, when the sward is not only
grow more vigorously, but has the highest quality. Where mating
lambs may be born in late winter and the ewes will need plenty of
quality of feed - at
of very slow pasture growth, although the growth rate is starting
slowly rising plane. 'Plenty of feed' can be defined as being
with a sward height of at least
4 cms, which is generally regarded as
1,200 kgs of dry matter per hectare. Studies have shown that a
of this height allows maximum intake by the ewe, and maximum
But it also means moving the sheep before the sward height drops
because at this height, there is not enough feed, and additional
is used in grazing extremely short grass. At 2 cms sward height
ewes will have to draw on
fat reserves for part of their daily energy needs. The ewes start
weight, and the lamb in utero
is not adequately provided with
Some regard a residual sward
cms (representing about 1,500 kgs of dry matter per
hectare) as the level which should not be transgressed. This
sward height of at least 7 cms at the start of grazing. The
that a 7 or 8 cm sward will grow the deepest roots, result in a
increase in soil carbon, build ability to hold water, have
mineral exchange capacity via increased humus, and provide a
profile which sustains a higher earthworm population.
The first six weeks after lambing make heavy demands on the
ewe (sheeps milk is very rich - 30% fat, and high protein). She
sward that can provide the greatest possible amount of high
Nutritional requirements for a 60 kg ewe feeding a lamb are
2.6 kgs of dry pasture matter (13 kgs fresh sward per ewe on
calculations) per day, and more for a larger ewe feeding twins.
realistically, the requirement might be 4 to 6 kgs of the highest
lush sward per ewe per day (less for a smaller ewe, more for a
with twins). This peak daily feed requirement in the yearly cycle
fall in early and mid spring. This means the sward has to hit its
at this time. Ryegrass has been the grass of choice to fit this
in shorter grass swards, and tall fescue and cocksfoot does the
long grass swards.
As a very rough estimate, the ewes and lambs should be presented with a sward at least 4 cms, and preferably 6 cms high, and shifted to similar height pasture when it is eaten down to between 2 and 3 cms. (There is no additional weight gain on even higher sward.) This means that the sward should be managed to include strongly growing grasses such as ryegrass and some tall fescue varieties that are both productive and also peak their production in early to mid spring. It is also essential that the sward is 'high quality' - each mouthful should contain as much energy and protein as possible, and contain no anti-nutritional factors.
Fresh immature grass species typically have about 3% metabolisable protein per fresh kilogram (12% crude protein per kg dry matter). This is broadly the same protein content as 'nutritious' grains such as oats and wheat - and higher than maize seed. Only phalaris has a significantly higher protein content than other grasses at the immature seed head stage.
Legumes - and particularly white clover - have a higher crude protein content than actively growing immature grasses. The crude protein is typically around 15% per kilogram of dry matter. A mature clover plant has about the same dry matter content as lush immature grass (23%), so a kilogram of fresh clover contain very roughly 4% crude protein. Higher protein legumes are broken down more rapidly in the rumen compared to grass. These high proportions of protein in the rumen content (relative to carbohydrates and to less digestable fibrous/lignin-containing forage) means that the nitrogen content is not used as efficiently as it would be if better balanced with fibre or carbohydrate-containing forage. As a result, the dung and urine contain more nitrogen than would otherwise be the case.
Paradoxically, soluble proteins, whether from lush grasses or legumes, can form a foaming mat in the sheeps rumen, preventing gas escape, and inhibiting feeding until it is belched out (a condition known as 'bloat'). Plants with condensed tannins - lotus, sulla, dock - bind and precipitate the soluble proteins and by-pass them out of the rumen to the intestine for digestion, improving the overall efficiency of use of the protein content in these legumes. These plants do help reduce bloat where they are present in sufficient quantity (1- 3% by weight), but a major factor increasing the risk of bloat is introducing hungry animals to lush pasture, when they gorge on large amounts of highly fermentable greens. The 'protein fermenting' enzymes within the plant cells are released when the leaves are chewed and placed in the ideal fermentation conditions of the rumen. The proteolytic enzymes coupled with microbial action can result in fast release of both gases and bio-foams, with potentially disastrous results.
If winter-active pasture species are selected and matched to the correct stocking rate, the sheep will always have good quality grass available, they will not need to gorge, and the increasing tempo of grass growth in spring will match the increasing appetite of ewes in late pregnancy and in early lactation. Where feed is unexpectedly short and animals have to be turned out on lush winter saved 'feedbank' areas, it would be ideal if the stored green feed sward included a good percentage of lotus.
Modern pasture species have been bred to maximise protein content. As a result, plants have tended to have relatively low amounts of energy-providing soluble carbohydrates ('fructans', fructose polymers, are the main carbohdrate storage form in grasses) relative to their protein content. Imbalance between the soluble carbohydrate content of the plant and the protein content has meant that the protein is not fully metabolised. When grass and clover is lush in spring and autumn (and wet summers), there may be more protein than the microbial flora can use. The excess ends up as unused ammonia, which is absorbed into the bloodstream from the rumen. Ultimately, it is excreted in the urine. In the worst case, (mainly involving dairy animals and under unusual conditions), up to 40% of the nitrogen in the sward eaten is lost as methane and as ammonia.
Some pasture cultivars have been bred with increased levels of soluble carbohydrate, which increases the efficiency of the use of the dietary nitrogen ingested. In addition, they compensate (in part) for decreasing protein content as the grasses mature and decrease in protein while increasing in lignin content. 'High sugar' winter active Lolium and Festucalolium cultivars may be a worthwhile investment for better quality late spring/early summer feed for lambs. The caveat is that excessive carbohydrate (especially where sheep pellets are also being fed) in the sward may be implicated in one form of lameness, laminitis, a painful swelling of part of the hoof. Lolium and Festuca arundinacea both have some of the highest levels of water souble carbohydrates, particularly in spring.
Some roughage, whether hay or coarser grasses, may be useful to 'balance out' the percentage of protein, soluble carbohydrate, and relatively poorly fermentable 'coarse' lignaceous and cellulose material that might help rumen health. This may be particularly important in spring and autmn when rapidly growing ryegrass is dominant. But structural carbohydrates, such as the lignins that give grasses leaf rigidity, have been reduced in some cultivars.
Paradoxically, it is possible that coarser-leafed grass cultivars with good fructan and protein contents might provide the best balanced solution for achieving both maximum lamb growth and minimal health problems due to lush feed and excessive protein and/or carbohydrate. (Keeping hay available at all times might achieve the same result).
All the legumes - white clover, red clover, and lucerne - are noted as excellent growth foods at all stages of plant maturity. In this respect, they are at least as valuble as grasses, as, in complete contrast to grass, their protein content doesn't change markedly with life-stage. But in winter, clovers grow very slowly.
The problem is mirrored in summer. The need is to keep clovers active long enough into the summer to mature the lambs to a larger size, if that's what you want (a typical weaner lamb killing out at around 12 kg carcase weight at 4 months may put on several more kilos over the next few months, or grow relatively little, depending mainly on on its health and the quality of feed available). Of these legumes, white clover is probably the most valuable in low-care large orchards. It will grow all year round except for dry summers; and there are now more dry tolerant cultivars becoming available anyway. Hopefully, by the time it stops growth due to dry, even late born lambs will be big enough to sell or kill. If you could be bothered, you could grow separate strips of pure white clover to 'pump up' lamb growth in spring and early summer (lamb growth is even faster if some ryegrass is also - separately - available). The downside is that the clover will all but disappear in the midsummer heat. Red clover is more seasonal, but if managed correctly, can provide good summer feed. Caucasian clover also has a reputation for summer persistance, but it has not been used much, as it requires extra care for several years to get established.
A few breeds - mainly merino, dorset, and some northern european short tailed breeds - can mate in late spring and lamb in autumn if the ram is kept with the flock. This partly fits in with sward productivity - flushing is in mid/late spring when feed is plentiful and lambs nearly weaned, and late pregnancy overlaps with late autumns plentiful feed. The sward really needs a late autumn 'bagged nitrogen' dressing to keep it growing as long as possible into early winter when the lamb is born. The lambs are born when there is least amount of pasture available to support heavily lactating mother sheep. Therefore, winter active pasture grasses such as fescue and perennial ryegrass are essential for this strategy; as is ample reserve pasture. Winter lambing has the greatest mismatch to seasonal sward growth, and should be done conservatively, or not done at all.
The objective is to match the changing needs of an appropriate number of sheep throughout their lifecycle with the amount and seasonal growth pattern of the particular species in your sward. The trick is not to overgraze the sward to the extent root growth and therefore drought resistance and fertiliser responsiveness is compromised, but to sustainably 'push' the grass and legumes to produce the largest amount of nutritious plant parts at the most critical times for the sheeps needs. Some factors affecting grass growth (mainly the weather) can't be controlled, and some can. The availability of key plant gowth nutrients is one of the most important factor under the orchardists control. Limited plant-available nitrogen is an almost constantly present factor - regardless of the time of year - that stops the expression of the full growth potential of the grasses of the sward.
Thus nitrogen is the key element for plant growth. Whether from a bag, from urine, or from decomposition of organic matter, it is the same element. The commonest plant-available form of nitrogen is nitrate. This is produced as a regular part of the cycle of decomposition in the soil, but the amount is severely constrained by the soil temperature, availability and spatial distribution of organic material, and seasonal cycle of biological activity.
In contrast, bagged chemical forms of nitrogen (such as urea) are available independant of the seasonal peaks of soil organism activity, can be spread evenly, and make nitrate available to plants roots within about 2 weeks of application. Under very good growing conditions, there can be a response of 25% or better in pasture dry matter within 3 weeks of application of moderately high rates. The response is visible after about 10 days of application. In good growing conditions, the extra growth response continues for about 6 weeks, then tails off rapidly.
But if conditions for plant growth are good, clovers and other legumes should be 'doing the job' of supplying nitrogen. Bagged nitrogens greatest value may be in winter, in times of poor growing conditions for clover; conditions which also give relatively poor sward response to nitrogen from any source. But in winter, even a limited growth response is worth having.
Winter growth response depends on there being an actual deficiency of nitrogen - some winters are warmer and drier than others, and there may be good winter growth without additional nitrogen. Other elements, such as potassium, must not be markedly deficient, and the pasture species must be those that grow well in winter (ryegrass, prairie grass, Poa annua, Kentucky blue grass, cocksfoot, tall fescue, Yorkshire fog).
Bagged nitrogen fertiliser
The pace and timing of biological processes that contribute nitrogen to the sward are often mismatched with the needs of pregnant ewes and rapidly growing lambs. This is the most important reason for using bagged nitrogen. And when there are no legumes present to fix atmospheric nitrogen into the soil, there is little practical alternative to using bagged fertilisers on swards (recognising that well decomposed compost can be used under orchard trees - except that the greatest amount of nitrogen will not be released until biological activity accelerates rapidly in spring).
Urea, a salt derived from ammonia gas and carbon dioxide, is easy to handle (it is granulated and coated with inert material to prevent absorption of atmospheric moisture and ensure free flow), is one of the most concentrated forms of nitrogen (at about 46% elemental nitrogen), relatively cheap, and is in a useful form - in that its conversion to soluble nitrate takes place over one or two weeks thus lessening the risk of loss from leaching into the groundwater. Urea does, however, temporarily form ammonium carbonate under the influence of an enzyme in the soil. This creates a short-lived alkaline condition, which converts some of the ammonium to to ammonia gas which in turn volitises off into the atmosphere under warm, windy, and dry conditions. In cool soil conditions the enzyme works too slowly to create markedly alkaline conditions, and little nitrogen is lost.
Sodium and ammonium nitrate provide 'instantly soluble' and thus 'instantly available' nitrates, but unless they are used immediately by the plant, they are suceptible to being quickly leached out of the soil by rain. They are not affected by volitisation in warm conditions. Its advantage is that it is not dependant on nitrification processes by soil bacteria to create the soluble nitrate ions, and so provides unconstrained instantly available nitrates in winter when soils are cold and bacterial and enzyme activity is very slow. If ammonium nitrate is mixed with basic fertilisers such as lime or rock phosphate, it will tend to lose some of its nitrogen content in storage.
Sulphate of ammonia is about 21% nitrogen and 24% sulfur. It is not affected by volitisation. The highly soluble ammonium ions tend to displace calcium ions (and other basic ions) in the soil. Calcium sulphate is formed, which is more soluble than the soil calcium carbonate (lime) from which it was (in part) derived.The calcium sulphate washes out, tending to leave the soil more acidic than it was previously. Sulphate of ammonias acidifying effect can be neutralised by applying about the same weight of lime some weeks later. It is slightly more expensive than urea.
The question is how much nitrogen to use. Application rates under about 20 kgs/N/hectare (2 grams per square metre, e.g. 4 grams - about a teaspoon - of urea form of nitrogen) produces relatively little response. From about 50 kg/N/hectare (5 grams per square metre, e.g. about 10 grams of urea, roughly a level spoonful ) onward there is the potential to gain approximately 25 kgs of dry matter for every additonal kilogram of nitrogen applied, until high rates are reached (250 to 400 kg/N/hectare, depending on presence or absence of other limiting factors), when the response to each additional kilogram of nitrogen becomes less and less.
There is no doubt that where soils are moist and have responsive pasture species, there can be spectacular increases in the amount of grass when very high applications are used (say 400 kgs nitrogen per hectare in seperate smaller dressings throughout the year). Better than 75% increased growth on soils with high phosphate levels have been achieved. But at these rates, there is also four times higher nitrate leaching, and some research claims suppression of clover above 200 kgs/nitrogen/hectare/per year. 200 kgs nitrogen/hectare is equivalent to roughly 4 tablespoons urea per square metre (a moderate sized handful) per square metre. This is a lot of fertiliser. It is not necessary - or desirable - to go to these extremes to get some strategic extra grass growth.
In addition, for more shallow rooted swards, such as
nitrates are only taken up in the top 45 cm of soil. Heavy
of urea on a damp soil can move nitrates 150mm down with 50mm of
Thus, any nitrates not taken up by plants in the top 45 cms is
be moved out of reach after persistant or heavy rain - especially
draining soils. Nitrate leaching through the soil is negatively
charged, and tends to take positively charged basic minerals
magnesium, potassium or sodium) with it, accelerating natural
acidification and reducing the base exchange capacity of the soil.
Finally, there is some indication that heavily nitrogen fertilised grasses that have taken up addition nitrates have more rumen degradable protein than the balanced rumen can handle. This 'undegradable' protein is simply excreted in urine, with little, if any, additional gain in animal growth.
The most efficient pasture growth increases are achieved at
rates of 20-40 kgs/N/hectare. Higher rates give a smaller
in pasture growth per kg of nitrogen deployed. The total number of
in a year should be tailored by strategic consideration of the
in each distinctively different area of the orchard sward.
Excessive amounts of nitrate
Stock can handle some nitrate in plant tissues (About 0.1 of a gram of nitrate in feed per kilogram of bodyweight is generally recognised as probably safe - a 65 kg ewe could safely consume about 6.5 grams of nitrate), but high levels due to high application of urea can cause nitrate poisoning in stock. Lush feed, especially stemmy grass and herbs that are growing quickly (especially annual ryegrass and tall fescue), can build up high nitrate levels in their tissues. Usually, absorbed nitrate is quickly turned to protein. But excessive nitrate applications, especially in conjunction with environmental conditions that lead to nitrate accumulation - cloudy days with low light, or dry droughty conditions followed by rain - can result in an increase in the amount of nitrate in stems and leaves.
Nitrate is first converted to nitrite in the rumen and then
to ammonia which is used by rumen organisms. Nitrate conversion to
nitrite happens faster than conversion of nitrite to ammonia. When
much nitrate is present in the pasture consumed, nitrite builds
some is absorbed
into the bloodstream where it reacts with haemoglobin to convert
into methomoglobin, which cannot carry oxygen. The tissues become
starved of oxygen. Symptoms are dose dependant. About 0.3 of a
nitrate in feed per kilogram of bodyweight is considered
to a third of
haemoglobin converted produces only slight symptoms. It may be
scouring, poor appetite, and drowsiness. Iodine uptake is
thus thyroid function is impaired. Sub-acute amounts cause
unsteady gait, or, with greater conversion of
haemoglobin, collapse and shallow and rapid panting. Pasture
about 6 grams or more of nitrate in feed per kilogram of
will cause acute poisoning. Situations resulting in acute
from pasture are very rare. When 70% of the haemoglobin has been
converted convulsions, coma, and then death is
certain. Fortunately, sheep are less suceptible than other
and the danger is less if the sheep are introduced to higher
pastures gradually so the rumen microorganisms can adjust to the
levels. On-going, chronic nitrate poisoning is rare; occasional
level nitrate poisoning is more likely.
Introduce sheep to lush pasture gradually, especially if it is
or tall fescue (the species most likely to accumulate nitrates -
ryegrass and fescue with 'wild' endophytes may have a slight
effect due to the vasoconstricting endophyte phytochemicals
offsetting the vasodilating effect of nitrate). Be particularly
cautious if there have been periods of overcast or dry weather
immediately prior to grazing. Allow time for the rumen to adapt to
higher nitrate levels. Do not put weak or unhealthy animals on
suspected to be likely to have unusually high nitrate levels.
with hay (not
or fescue hay) or carbohydrate rich sheep nuts to limit initial
Pasture growth can be 'boosted' in early spring by applying some urea nitrogen (about 80 kgs urea per hectare, containing roughly 40 kg N). But this must be done carefully and sparingly. Better, don't let some strips become lush while leaving animals too long in other areas.
Worse, heavy applications can cause soils to become increasingly acid, and damage the vital rhizobia nodules on the roots of white clover that 'naturally' fix atmospheric nitrogen into the soil. White clover is not known as 'white gold' for nothing. It's act of 'pulling' nitrogen from the atmosphere into the soil means cost free fertiliser as long as it has what it needs to grow.
But urea applied before winter can both help to create high quality leafy feed to flush ewes in autumn and also capitalise on warmer winters by providing a residual boost to winter growth at a time when ewes have high nutritional needs. The greatest response comes from sward that hasn't been grazed too hard, or damaged by late summer drought. Younger swards, particulalry, respond to strategic nitrogen (typical rates are moderate, 20-30 kg/nitrogen/hectare) with increased numbers of tillers, and better tiller survival under grazing.
Autumn urea applications (typically at lower rates, e.g. 20 kg/N/hectare) to compensate for poor nitrogen fixation by white clover is one of the most useful strategies to maximise feed in winter when sward growth is severely 'pinched'. While clover will use applied nitrogen for its own growth in preference to 'fixing its own', nitrogen fixation is low in cool season temperatures anyway, so the forgone 'free nitrogen' from clover is a tiny cost relative to the large benefit to the grass.
When temperatures are high (around 83o F) urea volatises off much more rapidly in the prescence of lime. (Alkaline materials cause ammonium salts to give off ammonia gas.) For this reason, most fertiliser companies recommend a gap of around 2 months before applying urea to a newly limed paddock. Conversly, urea is 'fixed' in the soil within about a week, so liming can be safely done about a week after an application of urea, with no danger of altering the response to the nitrogen fertiliser.
Clover biological nitrogen fertiliser
Specialised bacteria living in 'nodules' in clover roots capture atmospheric nitrogen, which is used to build their own protein, and part made available to the host clover plant as ammonia in return for sugars manufactured by clover as a result of photosynthesis. This atmospheric nitrogen incorporated into the totality of the clover tissue in the sward is made available to the soil partly (about 25%) from decay of clover roots and stems underground (continual die off and new root growth means that virtually the entire root mass will have replaced itself over autumn), partly from the nitrogen rich clover leaf litter (clover leaves contain about 5% nitrogen), and partly (20%) from the urine and faeces created from sheep or other herbivores grazing the clover. Some nitrogen is lost from dung and urine, some is incorporated in animals bodies, whether insect, mollusc, or herbivore. Somewhere around 70-90% of the nitrogen content of that part of the clover biomass in the sward that is eaten by herbivores is initially deposited either on or in the soil in herbivore excretions. Much of this recycled clover nitrogen is subsequently captured by grasses to support grass growth; grasses, in particular, are much more efficient than legumes at taking up free nitrogen compounds that become available in the soil from decay or excreta.
Because the nitrogen from clover has to go via the decay process - or via faeces and urine - most mineralised nitrogen is used by grasses and herbs immediately it becomes available in the soil, whether directly in urea, or indirectly via soil organism decay. Nitrogen is also used in the growth in the constantly changing populations of the soil biota. As a result, most of the nitrogen in the soil is largely in organic form, and only around 1-3% of the total organic nitrogen is mineralised in the soil per year (one study 'model' claims 5-9%). As the rate of mineralisation is low, and the rate of uptake by plants is very high, very little of the clover-derived nitrogen is lost to leaching.
Clover, a legume and thus largely independant of soil nitrogen, is particularly nutritious, and preferred by sheep when sward quality is sub-optimal. Clover in sheep swards usually ends up with small leaves and short internodes due to the constant grazing pressure. Probably the main factor limiting clover growth is lack of soil phosphate. As long as phosphate levels are adequate and the soil is not too acid, white clover should grow well in moist soils. It is subject to a number of pests and diseases (root nematodes, root and leaf eating weevils, slugs, viruses, etc), but if your clover is badly affected, it is probably not worth doing much about it.
But letting grasses grow too tall will shade out most cultivars of clover. If grass gets ahead of your stock in spring and autumn, it pays to mow it if you can. The amount of mulch obtained is probably more nuisance value than use, but if you want to increase pasture growth naturally, you'll have to top rankly growing grass before it suppresses the clover, especially if you don't have some hungry lambs and lactating ewes to soak up the excess.
The highest recorded amounts of nitrogen fixed by red clover and by subterranean clover are roughly 200kg of nitrogen a hectare. The record for white clover is about double that. Only pure stands of lucerne can match it. More typically, white clover contributes anything from 100 kg to 350 kg of nitrogen per hectare per year, depending on temperature, amount of clover in the sward, effectiveness of the strain of rhizobium infecting the clover roots, vigor of the plants, soil moisture over summer, and soil fertility. The percentage of clover in the sward, and summer soil moisture availability are the major influences. In one trial, low (around 8%) amounts of clover has been measured as contributing only around 24kg to 48kg nitrogen/hectare/year - and this may be fairly representative. The greatest contribution of clover-nitrogen comes at around 35% clover content in the sward.
White clover contributes relatively little nitrogen in winter as it grows very slowly at temperatures below 10oC, and provides very little extra nitrogen to the grass and herb component of the sward. At this time, a large part of the clover photosynthetic product goes to support the roots. The roots nitrogen fixing activity more or less matches the temperature-driven low requirement for leaf growth at this time of year. Thus, when temperatures are low, adding nitrogen makes no difference to clover growth. And as nitrogen fixation is much lower than later in the year when it is warmer,white clover produces relatively little excess nitrogen to boost grass growth in winter. In contrast, ryegrass leaves will expand and grow relatively well in winter provided it is not limited by lack of nitrogen. Fortunately, trials have shown that autumn and early winter applications of low rates of nitrogen (45kgsN/hectare) does not suppress clover growth in the subsequent spring, but does boost winter grass growth.
Until winter-active clover ecotypes are selected (possibly from northern Eurasian white clover populations), urea or other nitrogenous fertilisers will have to take white clovers place in winter. Winter active annual clovers, such as subterranean clover or balansa clover, could be used; but their persistence in the sward is dependent on successful annual seeding.
Animal biological nitrogen
Urine contributes useful amounts of nitrogen to the soil, albeit highly localised. Between 60-90% of the nitrogen in the portion of sward-grasses, legumes, and herbs consumed by cattle is initially returned to the soil in their urine. Presumably the calculation for sheep is similar.
The ammonium is converted to the negatively charged nitrate (NO3–) form by soil bacteria ('nitrification') over the next one to six weeks. The peak of available nitrate throughout the top 150mm of damp soil is very approximately at 3 weeks from urination. (The rate of nitrification of urine nitrogen in winter is probably not limiting in the climatic conditions of the warm temperate zone; except that the rate drops off in waterlogged conditions.) Peak nitrate availability close to the surface layer of the soil is earlier, at around 10 days. But if surface soil conditions are dry, little early response from surface nitrate availability is possible. The fate of the nitrate ions released by nitrifying bacteria over this period is determined both by the soil moisture and by the weather. In dry conditions, nitrate accumulates in the soil, and little will be taken up by the plant until it rains.
Being negatively charged, the nitrate ions are repelled from the clay particles surface, and remain free in the soil water. Here, they are available to be taken up by grasses and herbs. Nitrate ions are removed from the soil by being taken up by actively growing sward. The dark green grasses in urine patches will typically have greater than 4% nitrogen content on a dry matter basis, making the grasses more palatable, and acting as a 'sump' for free nitrates as they become available. But if there is heavy or persistant rain to the point that there is water draining from the soil, a portion of the higher nitrate concentration under localised urine patches will be lost from the root zone with the draining soil water before it can be captured by the sward plants.
Animal biological nitrogen is really nitrogen 'borrowed' from the soil via the plants ingested. The nitrogen is returned in urine and dung, and, in a natural system, when the animal dies and decomposes. Of course, the nitrogen in the protein of animals bodies is removed when we harvest them for eating. In addition, urine concentrates nitrogen and makes it liable to gassing off as ammonia (in the right circumstances); nitrogen may also be gassed off from moist dung. So there is a nett loss of nitrogen from the sward - in the absence of legumes. Legumes can cancel out the nett loss. Soil organisms release nitrogen from decomposition of plant and animal material that are on and in the soil.In a clover-grass sward, the nitrogen in the dung is not well used (on the other hand, little is lost through volatisation, as its free ammonia levels are low), in that total soil nitrogen availability (dung plus clover) is not raised much above what is available from the clover alone. It may be that most nitrogen from dung is ultimately immobilised in the soil in organic forms. In warm conditions, more nitrogen becomes available from this mineralised organic 'sump'; but it is just as quickly used up in the temperature-mediated proliferation of soil macro and micro organisms, which also need nitrogen for growth and reproduction. The release of nitrogen from dung is slow. Nitrogen in the soil solution (within the first 50mm of soil) directly under sheep faeces increases very slowly, and peaks at about 2˝ months. Dung might improve soil structure though building organic material, but contribute relatively little nett plant available nitrogen. In cool conditions there is less microorganism activity, and there is consequently less nitrogen available from the cycle of synthesis and degradation in the soil.
The amount of nitrogen in the organic matter as a whole varies according to the woodiness or lushness of the material decomposing, the rate of deposition, and the rate of decomposition and oxidation. Of the nitrogen present in soil 'organic matter', probably around half is in protein, about 10% in amino sugars, a small amount in humus. The origin of the remainder is uncertain, but will include soil microfauna, such as nematodes, mites, collembolla, millipedes, insect larvae, worms, and other soil animals which live on dead plant and animal organic matter, microfauna faeces, and microfaunal remains. The quantity is hard to estimate, but is very large - one estimate is 10.2 tonnes in the top 15 cm of an acre of land. (And of that, an estimated 4 tonnes are bacteria, 4 tonnes are fungi, and 1.6 tonnes are earthworms). These animals are very short lived, and as their bodies decompose quickly, are a constant source of nitrogen.
Soil bacteria are at the end of this chain of feeding and decomposition by ever smaller organism, and they ultimately convert the residue to carbon dioxide, mineral organic salts and nitrate that cannot be used as food by soil microorganisms - but can be used by plants.
Thus nitrogen is mineralised following decomposition of plant and animal organic matter by soil organisms. The rate at which some of this is then re-released as ammonium and its nitrate conversion product is temperature dependant. The amount that is released is related to the ratio of 'stemmy' high carbon material to 'lush' high nitrogen material in the plants and dung being decomposed, and to time. The sprayed out underground stolons of kikuyu, for example, require more nitrogen than their decomposition contributes. Thus, in the shorter term, they are a nett user of soil organic nitrogen, rather than a contributor; but in the longest term the soil-based nitrogen used in breakdown of the cellulose component is returned via death of the soil organisms that fed on the cellulose, as is a large portion of the original nitrogen content of the stolons. A natural sward that includes legumes will thus slowly build up its nitrogen content over the years.
But undisturbed soil under sward has a natural ceiling of mineralised nitrogen above which it does not go - about 0.25%. Conversely, the soil under a cropped field, even if it is never fertilised, will not fall below 0.1% nitrogen content. Some soils developed without cropping - especially low fertility sands in drier regions - may have very low initial nitrogen content ( in near pure sands, as low as 0.05%)
Total organic matter in the surface layers of a grassland soil thus reaches an equilibrium. Organic matter is added from faeces and from plant and animal death, soil organisms feast on it all, releasing carbon dioxide to the atmosphere, and total soil organic matter fluxes within bounds dictated by the mineral fertility of the soil, and the amount and pattern of warmth and moisture through the year. High carbon/low nitrogen material such as autumn leaves may accumulate temporarily, but as soils warm and soil fauna and flora proliferate, even this excess organic matter is consumed by the soil.
Grassland soils, in particular, can accumulate organic matter
top 30 cm where fine fibrous grassroots are most active. Winter
may continue to grow at a time when decomposition organisms in
are less active, creating a build up of organic material prior
Winter active and deep rooted summer drought tolerant grasses
builders of soil organic content over time.
Worms and the sward
Worms are naturally abundant in undisturbed grasslands, and their numbers, while hard to estimate, can be very high - in ideal conditions, one estimate is over 2 million worms per acre. Heavily limed soils have had average worm counts of 1,070 worms per square metre. Worm numbers drop fairly rapidly if the sward is ploughed or rotary hoed, but they rebuild rapidly. Earthworm numbers peak in winter and spring, and many die in the dry of summer. Worms incorporate into the soil nitrogen-containing material, such as leaves, decaying animal flesh, and sheep droppings by dragging it into their burrows and eating it. Casting species of worm, such as those in the genus Allolobophora, will drag sheep pellets to their burrow entrance, where they make small mounds of pellets like a pile of miniature cannonballs.
Worms have small mouths, and as they eat soil in making their burrows, their casts are of particles no greater than their mouth size - 2mm. The particles may be fine silt or clay fractions, which are thus mingled with organic matter. Minerals are thought to become more available once having been mixed and mingled in the digestive tract of worms.
If this is the case, they may usefully contribute to overall soil fertility. One estimate is that between 4 and 36 tons of soil per acre per year pass through worms. The weight of finely sorted organic and mineral particles in casts excreted by cast forming species might be 1 to 25 tons per acre per year. Casts may also have a negative affect, at least on some specific soil types. On poorly drained soils with fine structure, these casts may disintegrate in winter, and form a drainage-impeding surface 'glaze'. The combination of wet soil surface and fine sediment 'cast-glaze' makes the sward suceptible to damage from 'pugging' by sheeps hooves in winter.
As earthworm burrows and activity is largely confined to the top 15 cm, the drainage effects of the burrows is somewhat limited.
Their most useful service in the home orchard is in removing autumn leaf fall. Deciduous leaves and catkins are dragged into their burrows over this period, with some material, such as alder catkins, used to plug the entrance. This industrious clearing of leaves allows shade tolerant grasses near shelterbelts to regrow through the slowly diminishing leaf litter.
It is often claimed that fertiliser applications harm worms.
little evidence that this is so; except that very high rates of
ammonium sulphate are sometimes used in turf to
casting worms. This effect is most likely from the effect of the
on soil pH - dropping it into the acid range, which is an
for worm activity - rather than any direct physical effect. It
that under some conditions, very heavy applications of a highly
salt, such as potassium chloride, may have an irritating effect.
used at the normal rates, have either only localised and
effect, on worm numbers.
In any event, the aim is not to graze the sward too heavily, or the roots are weakened and the plants lose drought resistance. On the other hand, the pasture can't be allowed to get so lanky that it shades out the more prostrate but light dependent clovers. Clovers and other legumes are the engine room of the sward. Ideally, sheep will be stocked heavily enough that they are forced to eat the less palatable species as well. This prevents the most palatable species being hammered, having only root reserves of carbohydrate to draw on in order to grow new leaves (the fructan reserves stored in leaf sheaths and shoots having been removed by the sheep), and growing weaker and weaker. In the meantime, the worst species are left alone to grow on and ultimately dominate the sward. A heavily grazed preferred species puts up tender new growth as it re-grows. As sheep prefer new regrowth foliage, this is selected again and again, becoming weaker and weaker unless it is allowed to recover. It will not be able to re-grow until the sheep are finally shifted out. This means that ideally the orchard should be able to be grazed section by section, and that the sections are small enough (or the flock large enough) that the area is grazed out within 5 days or so. If the sheep numbers are so small, or the area so large that the sheep remain in the same place for weeks at a time, the most palatable species simply can't recover.
The objective is to have the 'right' number of animals for 'right' number of enclosures of the 'right' size and the amount of seasonal growth of the 'right' nutritional value.
But no two seasons are alike, and the sward is often in slow shift of composition. A constant close match between animal numbers and optimal grazing height is therefore unlikely, no matter what the 'ideal' advice is. Usually there will be too much or too little sward, and the sheep will typically graze some species too heavily (down to the growing point close to the ground) while leaving others standing lush and tall. Mowing, supplementary feeding, and the selling and buying in of lambs are additional techniques to cope with the inevitable mismatches in the pastoral system. The aim is to match animal numbers and seasonal pasture growth as closely as possible as much of the time as possible.
Unfortunately, predicting how long a given area of sward will 'last' in summer and winter is more art than science. Using a carefully calibrated device, a 'falling plate', is useful in intensive commercial dairy production where the lush-grass/tall-clover 'duoculture' is homogenous, long, and often sprawling as much as upright - but it is of little use in the upright, often tightly clipped sheep swards of 5 cms and less. While measuring standing sward height with a simple ruler (from 2.5 cm above the soil surface to averaged grass/legume/herb leaf tip height) can give an idea of how much dry matter is available at any one time, such estimates are often biased by the patchy nature of sward height, highly variable and patchy species composition (in the home orchard, at least), the denseness or thiness of the sward, growth differentials in wet or in dry areas, and by the number of measures taken to get the average height. Knowing how many sheep you have, and whether they need 'plenty' of feed for growth (lambs), 'plenty' of feed for ovulation (ewes), or just 'maintainance amounts' (rams outside the breeding season), you could estimate their 'ideal' daily feed levels, calculate the area of a given enclosure, measure average sward height, thus estimate the dry matter present, and from that estimate how long the enclosure will 'last'. This is a waste of time in most cases.
Usually, available uncontaminated pasture availability can be judged by walking through the enclosure, noting how badly hammered the preferred species are, and whether less preferred species have been touched yet, and overall how much growth (uncontaminated by droppings) is present. The mental assessment is then made, "enough feed for another week/few days", or "they will need shifting tomorrow". This is the crunch point. Has the sward in the next enclosure in the rotation regrown sufficiently? It has to have grown enough that the sheep can be left there for whatever length of time is needed (while still feeding them appropriately well throughout their stay) to allow the sward in the next enclosure again in the rotation sequence to also finish growing sufficient feed.
Given a basic level of fertility, the season is the prime determinant of how quickly the sward will regrow. Experience of how quickly sheep graze off the sward in winter soon teaches the home orchard grower the stocking rate limits of the current area of sward. It also teaches how often the sheep have to be shifted for the current size and number of enclosures. (Individual enclosures may have their own limitations - an orchard area may be quickly pugged by the sheep in winter, but support better than average summer growth.)When grass is lush in spring and autumn, the limit to the number of stock is determined more by how badly contaminated the sward has become (sheep are reluctant to eat near their own faeces) in the restricted space of the orchard interrows, and how long to allow sheep to 'hammer' the preferred species in the sward.
No amount of experience can help when there is a 'one in fifty years' drought or cold period. All estimates based on past experience are then of little use. Adjusting sheep numbers to low levels 'just in case' of a climatically extreme event means the pasture will almost always be out of control unless a mower is used regulalry, which somewhat negates the point of using sheep to control orchard sward growth.
If summer has been dry and feed short, the rains of early autumn bring a flush of sward growth and the first chance to feed up ewes and the breeding ram to ensure good conception. However, rainfall can still be erratic and inadequate. Drought tolerant species may once more prove their worth. Kikuyu may still be growing very well even with limited rain, especially if nitrogen has been applied and the weather is still hot. Kikuyu should be kept to 'lush lawn height' - about 2 cm high - to encourage white clover in preparation for kikuyu's winter slow down and possible die back.
Autumn is the major seed sowing time. If summer brought severe
much of the white clover may have
wiped out. Time to consider
to replace it with more drought tolerant species like caucasian clover,
or go for more drought tolerant white clover cultivars. Time also
if you might be better off moving toward deep rooted more drought
grasses; and if so, which species and cultivars. Paspalum levels
assessed now - paspalum may be green in summer, but it is dormant
in winter. Better to spray out areas with a lot of paspalum and
to summer and winter active grasses. Autumn is the major time of
to do something practical to improve the productivity of the sward
'pinch' times of winter and summer.
Autumn may be the major seed sowing time, but beware of unseasonal 'drys' early in autumn. Sow only when the soil is thoroughly moist and rain expected. White clover establishes best when there is still good warmth as well as rain, making early autumn a good time to sow this legume. If conditions are right, it may be possible to heavily graze some existing pasture and oversow with white clover, as it needs only shallow sowing.
Consider if you should sow legume and grass cultivars with improved winter activity, or summer drought resistance - or some of both. Some grasses, such as tall fescue, are slow to establish. Early autumn is warm and moist enough to give the seedlings the best chance, whereas later in autumn may be too cool for the seedlings to establish well. Ryegrass will also germinate well at this time, but it is so vigorous at the seedling stage it will outcompete slower grasses. For this reason it is perhaps best not to sow ryegrass in a mix with slower establishing, less vigorous grasses.
Autumn weeds such as thistles become more apparent, especially where there are bare patches in the sward. The safest approach is to grub out the offenders, or use non-hormonal herbicides such as glyphosate - being very careful to avoid drift onto orchard trees. There are hormonal herbicides that selectively kill broadleaf weeds with minimal effect on well established clover (and no effect on grass), but any unseen fine drift can be very damaging to orchard plants, especially young plants and sensitive species. You really do need to know what you are doing; do everything absolutely correctly, and act conservatively if you are to use them in an orchard situation. There is absolutely no room for ignorance, inappropriate spray gear, error, carelessness, risk-taking, or laziness.
If you are determined to use a hormonal compound against broadleaved weeds in orchard pasture, there is a wide choice of active material. Hormonal formulations include 2,4-D formulations (e.g. 'Pasture clean', 'Baton' 'Relay'), MCPA formulations (e.g. 'Clean Sweep', 'Crop Care MCPA') MCPB formulations (e.g. 'Soft Touch'), MCPA/B mixtures (e.g. 'Select', 'Tropotox Plus'), formulations of Dicamba (e.g. 'Banvel 200', 'Kamba 500'), Mecoprop/Dichlorprop MCPA mixtures (e.g. 'Duplosan Super') or Clopyralid formulations (e.g. 'Versatill'). To repeat, you must be ultra careful to avoid drift onto your own or anyone elses trees. Try to use the new low-volatility formulations of the hormonal sprays. Remember - chemicals used to kill woody weeds are even stronger, and may be lethal to your trees when used incorrectly or inappropriately.
Chainsawing and then painting the stumps of woody weeds with
killer' type hormonal formulations is both perfectly safe and very
But spraying a 'scrub' or 'brush killer' preparation
woody orchard plants such as vines (unless they are dormant, and
the only woody plants in your home orchard), tamarillos, kiwifruit
the like, or near herbaceous fruit such as mountain papaya is
the distortion and/or death of your plants.
Apply a monthly dressing of a balanced NPK composite mix with trace elements (zinc and boron are particulalry important) to subtropicals, particularly trees that have an autumn growth flush (eg avocadoes).
This will also boost grass growth and help put condition back on ewes so they ovulate well for autumn mating. Ideally they will gain weight for a couple of weeks prior to and after mating ('flushing' the ewes to boost ovulation and embryo retention). If ewes are gaining weight (over 150 grams a day) over the mating period, there is good embryo retention. If the sward is very lush due to high fertility and warm rains, ewes can gain as much as 300 grams a day at this time - but this can reduce implantation and retention of the embryo, due to a hormonal effect.
The other aim is to have ample feed in front of ewes in winter (commercially, farmers aim for around 1,400 kilogrammes of dry matter per hectare near lambing time. Pastures can be short but leafy and still have high amounts of dry matter going into spring. Paddocks that are short, but not very leafy are not producing enough to keep the ewe sufficiently fed to not have to draw on body reserves when lactating).
If autumn has not been good, and you are a little overstocked,
worried about insufficient grass for winter, an additional
urea can be used on the inter-row pasture to boost growth - if you
winter responsive pasture grasses, such as tall fescue (or some
Liming to adjust pH if necessary can be done any time now ( if you are using urea, wait at least a week before putting he lime on).
Mid to late Autumn
Usually still warm, but usually with reliable rain. Perennial ryegrass grows strongly once the weather cools, as does tall fescue, cocksfoot and brome.
If you haven't already thought about it, now is the time to think about sward species composition, and especially how to increase winter and summer active species. Check the amount of paspalum in the sward. It may perform well now, especially if it is a bit dry, but it provides little winter feed. The same applies to kikuyu. If conditions in autumn are right (cool enough to slow kikuyu growth down, heavy rain and moist soil) annual ryegrass can be sown into a very hard grazed or severely mown kikuyu sward and paspalum dominated sward for additional winter and early spring feed.
Now is the absolutely critical time to sow winter active perennial ryegrass or phalaris so that it is well established for the mid-winter 'feed pinch' and the additional feed requirements of the early spring lambing season. Prairie grass and yorkshire fog are not as winter productive as phalaris or rye, but nevertheless produce moderately well in winter. Selected annual ryegrass cultivars will provide prodigous amounts of winter feed, but they are only a temporary sward component. Lightly graze areas oversown in early autumn with white clover so that the developing seedlings get the light.
If you are trying for heavier lambs for killing or sale by feeding into autumn, good livewight gain of at least 150 grams per day can be achieved by putting the lambs into inter-rows and areas that have at least 5 cms to 8 cms of actively growing leafy sward height of high feed value species such as ryegrass, phalaris, clover or trefoil. Special purpose chicory and white clover swards are probably richest. These larger lambs need to be gorging on prodigous amounts - 4-6 kgs - of fresh lush highly palatable feed a day to achieve these weight gains (about double the amount needed to 'flush' a breeding ewe before mating). Growing larger lambs at this time of year uses a great deal of sward resource, a resource that might be better left as a 'feed bank' for the winter pasture 'pinch' when every available bite is needed for the pre-birth and the post-birth lactating ewe.
A warm wet autumn and lush clover growth can lead to bloat - especially if growth is coming off the back of a dry spell and there is a high white clover component in the sward. Lush ryegrass re-growth also seems to trigger a need for coarser browse. Sheep may be looking for tannins at this time, so be aware that thin, less corky bark may be scraped from trees - especially stonefruit and tamarillo. Lotus commences into growth about now, and it can provide the tannins needed. Alternatively, cut foliage of trees such as pittosporums, white mulberry, or loquat; or provide dedicated areas with high tannin sulla. Chopped astringent persimmon fruit are also high in tannin.
Some autumns can be unexpectedly dry - verging on drought in some
Don't be tempted to severely graze areas of sward - graze lower
25 mm (near the limit that sheep can graze to) and the growing
damaged, and the regrowth needed for winter (once rains come) will
slower. Tall fescue should be grazed no lower than 4 cms. If you
that you won't have enough winter feed, get rid of surplus stock
ewes, buy in hay, or start training your sheep to eat sheep
tiny amount of molasses on them can tempt them to have that first
of an unfamiliar food).
While excessive nitrate levels is not a problem in the coming winter, autumn warmth may lead to sub-acute nitrate levels if there has been a dry spell which is then broken by rain, with a sudden burst of pasture growth. Sub acute toxicity can cause abortion in ewes. Be cautious.
Now is the time to encourage as much winter active grass growth as possible before the winter lambing season. If superphosphate wasn't applied in early autumn, apply it now to stimulate the legumes in the sward to grow strongly and fix nitrogen for grass growth before winter cool slows clover down to the point of uselessness. Superphosphate dressings can be given to newly established grass seedlings if it wasn't done earlier. While white clover produces precious little surplus nitrogen to stimulate winter grasses when temperatures are below 10oC, winter grasses are quite able to grow and respond to nitrogen in temperatures as low as 5oC. To compound it, biological activity that would release nitrogen from soil organic material slows right down. Unless there is a substantial 'feed bank' of 'locked up' well grown autumn pasture saved for winter feed, feed can only come from keeping winter grasses active in the coming coldest months. The key is readily available nitrogen beyond that available from urine patches. The response is a little slower as the weather cools slightly, starting a little more slowly, and tailing off slowly; in any event, whatever winter grass growth response can be had is dependant on adequate soluble nitrogenous fertiliser (urea) being applied now. If grass seed was sown heavily, it is likely to become nitrogen deficient at this time. Judicious nitrogen applications will keep it growing, as long as phosphates are also available.
Apply potassium (up to about 40 gms/square metre) if soil phosphate reserves are good, but white clover seems lacking in vigor (assuming root weevils and other pests and diseases are not to blame).
Conditions for sward growth are often bad. Soils are cool, especially in the shade, they may be waterlogged, there is less daylight, less sun, more fog and wet. Casting earthworms are very active at this time. Their casts of fine sediment helping to 'glaze' the soil surface and impede drainage, and the casts smear under sheeps hooves to contribute to the mud. On the plus side, they drag some sheep manure into their burrows at a time when other decay processes have slowed right down due to the cold.
In winter, and particularly the first two months of winter, growth of both legumes and grasses slows right down. While winter active grasses such as ryegrass will grow (and respond to applied nitrogen) as long as the temperatures in the soil are 5oC or above, clover remain more or less dormant until soil temperatures are much higher. Such consistently warmer soil temperatures don't arrive until spring (except that some well drained sunny slopes may have soil temperatures high enough to support active clover growth in winter). In the coldest conditions, if the soil temperature at 15 cm goes below 6 degrees Celsius, sward growth stops almost entirely. Feed value also falls.
As a very broad generalisation, closely cropped sheep sward has only about half the feed value in winter as in active growth in summer. As a result, relative to summer, the daily energy demand of around 11.5 mejajoules requires double the area of winter sward of at least 3 cms to meet energy needs. Putting it another way, a sward will support the flock for only half the number of days it would in moist summer conditions. Practically, when pugging, waterlogging and faecal contamination is added in, the flock will need shifting even sooner than that.
Early in pregnancy, enough feed for 'maintainance' is sufficient for a ewe, but by mid to late winter her daily nutrient requirements will have accelerated to 16 to 20 megajoules a day, needing roughly 2.6 kgs of fresh grass to satisfy. But by the time the ewes have progressively eaten down their orchard inter-row lanes and come back to the starting point, the sward may not have regrown 2 centimetres. This is called overstocking. Regrazing grasses before they have a chance to grow enough leaf to replenish their carbohydrate stores used up in initial recovery from grazing weakens the root system, slows regrowth thereafter, and reduces the ultimate lifespan of the plants. Adequate winter pastures largely determines the number of sheep that can be kept. The weeks immediately before giving birth are times of very high nutrient demand by the ewes. There simply has to be enough high quality feed in front of the now ravenous ewes that they don't have to go searching throughout the orchard for a bite (a common cause of mis-mothering of lambs).
One of the least productive times of year is also the time when high quality feed is critical. Choice of pasture species is therefore also critical. Kikuyu, for instance, becomes effectively non existant if there is a ground frost. Winter growing ryegrasses, tall fescue, and - albeit to a lesser extent - clover are key sward species at this time, as they have much higher nutritive value than other grasses, and ryegrass and some tall fescue cultivars grow well in cool weather. Tall fescue can be grazed down quite hard - to about 3 cms - but it must be allowed to grow back to at least 8 cms between grazings, or it will lose vigor. In any event, supplementary feeds may be needed to overcome winter growth deficit. If winter active grass and legumes weren't sown in autumn, winter is too late to do much about it. Similarly, it is rather late to be trying to boost pasture growth with nitrogenous fertilisers.
While ryegrass will grow so long as temperatures are above 5 degrees Celsius, if nitrogen wasn't applied six weeks ago, winter grasses will not be meeting their growth potential right now. Even so, a response to strategic nitrogen applications can be expected, albeit the amount of growth in response to the nitrogen applied is much less due to slower growth rates in cold weather.
It may be a good time to order grafted plants of the honey locust, Gleditsia tricanthos, a tree which produces large amounts of nutritious pods which fall over winter. The honey locust can produce as much as 110 kgs of highly nutritious edible pods per tree by 9 years of age in winter, and grass still grow right to the trunk. Selected seedlings will have 26% sugars in the pods. A reasonable guess estimates the pods would have twice the feeds value (ME) of good hay.
In winter, there is little concern for water for the fruit trees. But your sheep may be going hungry. Winter slows grass growth, and if there are frost, turns kikuyu brown. As sheep use their reserves and become skinny, they lose some of their resistance to internal parasites. When underfed, parasite loads that wouldn't ordinarily affect them can become debilitating, sometimes even resulting in death (if not treated in time). While ryegrass is an important cool weather sward species, be careful not to graze a ryegrass dominant pasture too low, even if feed is short, as the endophyte fungus that causes 'ryegrass staggers' is concentrated in the base of the plant (unless you have sown 'low' or 'no' endophyte cultivars), albeit concentrations are lowest in winter.
Broadleaf weeds, if not controlled in autumn, should be controlled early in winter (if necessary). See 'Early Autumn'.
Areas of sward that were sown to new pasture in early autumn will benefit from a light nitrogen boost; sward oversown with white clover will benefit from dicalcic phosphate, or a dressing of superphosphate.
Superphosphate in moderate amounts applied at the very beginning of winter gives a good winter growth response by winter active grasses such as rye and tall fescue. In very low phosphate soils this may be due more to having been limited by available phosphate than any nitrogen deficiency, but in most moist soils it is due to increased clover activity before the soils get too cold. If the sward is dominated by summer and autumn grasses, such as Paspalum (Paspalum dilatatum), there will be very little winter growth response.
Likewise, in the coldest part of winter the grass component of the sward is likely to be nitrogen deficient regardless of legume numbers and/or poor legume growth. There will be little additional growth of grasses no matter how much phosphate is applied unless nitrogen is also applied. (Although the legumes will start to recover, there is a lag until warmer weather before they may become predominant, large, and active enough to influence grass growth) An application of 60kgs of urea per hectare (about 2 level teaspoons per square metre) will increase pasture growth markedly, even if the soil is relatively low in phosphates. This mid winter application of nitrogen (regardless of legumes) will increase sward yield right through spring and into early summer. In contrast, - and especially in soils with low phosphate content - heavy dressings of nitrogen applied to swards that have good clover content will supress the fixation of nitrogen by the root nodules, and cause reduced nitrogen fixing activity in spring and early summer, and therefore reduced grass growth at these times. Unless phosphates are at moderate to high levels, nitrogen applied to high clover pastures may favor grasses and depress clover growth in late spring and summer. Ensuring appropriate phosphate availability, perhaps with a slowly releasing phosphate source such as fine ground phosphate rock, mitigates against this danger.
Some subtropicals (especially avocado) become somewhat nitrogen deficient at this time as root activity slows right down in the cold. Highly available potassium nitrate could be applied, to the benefit of the sward as well, but the trees will 'pick up' come warmer weather, so such dressings are only beneficial if you want to sell some of your fruit.
Late Winter and Spring
Late winter, immediately before and after lamb birth, are times when ewes have particularly high nutritional demands. The last winter month is usually a time of warmer air and soil temperatures and thus rapidly increasing sward growth. Even so, if late winter is cold, supplements may still have to be fed. If lambing has been arranged to co-incide with spring (as ideally it should), the rams should be out of the way, in poorer quality pasture. The best resources must go to the breeding ewes, especially if the late winter recommencement of sward growth is delayed.
Good pasture management - productive cultivars, well limed, good phosphate levels, ample legumes (or nitrogen fertilised) should have been set up in autumn going into winter with the payoff starting now. As a very broad estimate (variables include rainfall, temperature and soil type), a well fertilised sward, with good stock management, can produce about 60 kilograms of dry matter (the dried weight of the fresh plant material available for consumption) per hectare per day when rainfall is ample and the soil has warmed. This is equivalent to about 300 kg of fresh green sward/hectare; or 30 grams per day extra fresh growth in every square metre of sward. In a particularly warm spring, well managed pasture can produce100 kilograms of dry matter per hectare per day. This is much more than the stock numbers geared to the constraints of winter feed availability could ever eat.
In late winter and spring, 11 ewes plus twin lambs to the hectare
normal stocking rate) eat 45 kilograms of dry matter per hectare
This translates to approximately 225 kg of fresh green sward
hectare per day; or about 22 grams per square metre of sward per
Thus, under average conditions of some warmth, moisture and
and with cool weather active grasses such as ryegrass, ewes with
stocked at the conventional rate can meet their nutritional needs
leave 88 kg of daily new growth per hectare uneaten - and even
a warm spring. Tall fescue cultivars which head early in spring
be grazed quite hard (down to about 5 cms), or they will have
available for later in spring and summer, and plants will start to
lanky and the leaves less nutritious.
Conversely, cold snaps at this time of year are a fact of life.
rain drops soil temperature, and can stall pasture growth for
Mid spring is generally the time when desperate famine turns miraculously to plenty - it is usually characterised by the largest and most sudden growth flush of the year; some of which will be used by the rapidly growing lambs. If most of the orchard rows are in ryegrass and clover, there will probably be an excess of feed. But this excess doesn't provide much long material for a mulch to 'lock in' springs soil moisture to help the most vunerable fruit trees survive summer dry. Surface rooting orchard trees such as citrus and feijoa may be better with taller grass species in the inter-row sward.
Lambs should have high quality pasture as well as access to highly nutritious ewes milk. If the spring growth is not as good as hoped, it might be possible to arrange a lamb sized gap under a fence to an adjacent orchard row with good feed. This way the lambs get the best pick. Lambs gain weight significantly faster when they have good access to clover. Once they start eating significant amounts of sward they will suddenly make quite an impact on the speed with which an inter-row area is eaten out. As they eat about 2% to 4% of their bodyweight in dry matter terms a day, it is best if the pasture is as nutritious as possible.
If winter showed that you don't have enough winter active species in the sward - and also thinking about summer to come - you may want to renovate some of the orchard inter-rows with combined winter and summer active species, such as tall fescue. Or you may want to sow a 'dedicated' row of a strong winter feed combination such as a selected winter active white clover and a festucalolium cultivar, perhaps with some phalaris mixed in. In the very warmest area, chicory grows well into winter. Seed can be sown once the soil has warmed in early spring. Springtime, with its relatively assured rains and ample feed, is a good time to take an inter-row or paddock out of the grazing rotation for the six weeks or so necessary to establish newly sown grasses and herbs.
Apply a good dressing of superphosphate in late winter (for preference) or early spring to stimulate the legume component of the sward and thereby provide nitrogen for spring grass growth. Whatever quantity used, better results are achieved if it is split into a dressing now and another in autumn. Apply the second half (200 kgs/hectare or roughly 1 and a quarter tablespoons a square metre) of the split heavy (400kgs/hectare) dressing used to build phosphate reserves in low phosphate soils.
Lush spring growth may be low in animal-available magnesium. If foliage magnesium is somewhat low, and if heavy potassium dressings has been applied, it may predispose lactating ewes to 'grass staggers'. It may be prudent to apply dolomite lime (180 kg/hectare), serpentine super (400 kg/hectare), or other magnesium fertiliser to the sward as a precautionary measure.
If the sward lacks a decent legume component it is not too late to apply nitrogen, so long as heavy applications (400kg urea/hectare) are avoided, as there is some evidence that heavy applications may suppress clover post-winter stolon regrowth. Response to applied nitrogen usually takes about 6 weeks, so the soil has to be warm enough in late winter for a good mid spring response. Looking ahead to mid summer, if you lack a strong legume component in the sward, it would be wise to apply nitrogen in mid spring to build up grass vigor in preparation for a feed bank to carry the sheep as long as possible into summer. Kikuyu, in particular, can produce an initial growth response of an extra about 800kg of dry matter per hectare when dressed with 100kg urea per hectare. Using 200 kg of urea/hectare nearly doubles the quantity of first growth.
Apply extra phosphate and dolomite lime to areas that will be sown with clover this coming autumn. Avoid liming near citrus, or use judicious amounts of calcium sulphate.
Early spring is, in general, the best time to put fertiliser around nut trees, and pip and stone fruit trees. The nutrients are washed in by spring rain; deciduous trees will be leafing out at the end of the first month of spring; and soils are warming, promoting growth. Subtropicals need multiple small dressings throughout spring, nothing in summer (unless wet), and further dressings in autumn. A typical 'orchard mix' contains, by element, 5% nitrogen, 5% phosphate and 5% potassium. This lower analysis fertiliser is broadly suited to nut trees, pip and stone fruit. It is also suitable as a 'baseline' dressing for subtropicals, but only the sulfate form of potassium salt should be used. This fits in well with fertilising the sward. Clover is only just becoming active in early spring and therefore the sward could use a boost of nitrogen from urea, and early spring is also a suitable time to apply superphosphate. But, while the rows of fruit and nut trees will need a potassium component in the mix, potassium is best left out when dressing the sward in the inter-row, in order to help prevent triggering a potassium induced magnesium deficiency in the lactating ewes. (Potassium can be applied in autumn.)
Pelleted compound fertilisers may have a higher concentration of nutrients, especially nitrogen and potassium, and typical analyses might be 12% nitrogen (often in a mix of fast and slower release forms), 5% phosphate (most in a water soluble form for an 'instant hit') 14% potassium (almost always in the sulfate form so it can be used on chloride sensitive plants like raspberries). These fast acting but slow dissolving pellets are ideal as monthly 'supplemental' feeds for subtropicals through spring and autumn.
Trees that require reliable prescence of trace amounts of boron (apples, apricot, plum, pear, avocado) may benefit from having boron supplemented superphosphate applied - particularly on sandy soils, where boron is apparently relatively easily leached through. Boron is not required for animal health, and has extremely low toxicity, so once rain washed, pasture is safe to graze at normal superphosphate amendment rates.
Fruit trees may need additional urea (for example citrus) or potassium (stone fruit on sandy soils). It can be useful to allow grasses to grow right up to the trunk of the trees, at least until about midspring. Grass can help shade the soil from drying out in short dry spells. Nitrogenous fertiliser is partially captured by the grass, and so long as it is later sprayed out while still green and lush it will both release the nitrogen it has taken up as it decomposes, and briefly become mulch for late spring, at least.
Late Spring and early Summer
Ryegrass, a cool season grass, puts on its greatest growth at air temperatures of about 18oC. White clovers' maximum growth happens at 25oC. Late spring/early summer is the time when these two species growth rates are most closely matched. As a result, the clover content increases markedly at this time. The increased nitrogen from the clover, coupled with the increased biological activity/organic nutrient recycling in the soil, results in greater grass growth.
Sward at different stages of growth has greater or lesser amounts of available energy. Some potentially useful energy from the digestible part of the plant will be lost in the urine, and some otherwise usable energy will be lost from methane evolved in fermentation in the rumen (and some pasture species result in more methane than others). Once these losses are discounted, the amount of energy a sheep can extract and metabolise from a unit of dry matter is the available 'metabolisable energy'. In the warm, well-watered conditions of late spring and early summer grass feed value is particularly high, but rain often starts to tail off in early summer. As grasses mature in the drier weather the amount of metabolisable energy available to the sheep in every kilogram of grass dry matter drops by about half. This is mainly due to the tillers sending up rather coarse flowering stems which soon become 'strawy' as the seeds mature. The relatively large lignin components in these stems can't be digested.
If the inter-row sward has a good component of taller grass species such as cocksfoot and tall fescue, they should be kept grazed to discourage heading for as long as possible. But once grass tillers have started to elongate their stems, the growing point, previously near ground level, becomes vunerable to being eaten. Grazing at this point will kill the tiller, because the regrowth-point is gone. At this 'early jointing stage' the ground level basal buds are fairly inactive, as the plant is concentrating on elongating the stems of existing tillers for the annual reproduction effort. As a result, regrowth is poor. Mowing or grazing once the grass has headed is no problem, as the grass is then usually ready to revert to the vegetative phase, and quickly initiates new basal buds and leafy tillers with 'compressed' unelongated stems.
In 'wild' endophyte-affected tall fescue pasture, the endophyte fungus is most active near the crown of the plant. As a result, the vasoconstricting alkaloid 'ergovaline' is most concentrated here (it is not very soluble, so relatively little is present in the leaves). Don't let the sheep graze too low, or they ingest too much alkaloid and suffer greater heat stress than would be caused by rising spring temperatures alone. Some sheep will suffer mild intestinal inflammation, with resultant scouring (diarrhea). In ryegrass, the alkaloid 'lolitrem' is also present, and the alkaloid in the incipient basal flowering tiller is carried up with the flowering stem as it elongates in early summer. The amount of alkaloid produced increases as the season progresses into summer, making careful grazing of wild endophyte infected tall fescue and ryegrass very important. (the other common sward grass beyond Festuca arundacea and Lolium spp that hosts potentially anti-nutritive endophyte fungi is Festuca rubra). Sheep will avoid affected ryegrass, in particular, where they have the choice. If the uneaten patches are not mown or sprayed out, they will eventually come to dominate the sward - a most undesirable effect. If excess sward is available, these 'least preferred patches' could be sprayed out and re-sown with endophyte free fescue or ryegrass, novel endophyte fescue or ryegrass, or other grasses species that are naturally never infected with 'antinutrituive' endophyte - grasses such as Poa, Bromus, Dactylis, Phleum, Anthoxanthum, or Agrostis (e.g. Kentucky bluegrass, prairie grass, orchard grass, timothy, sweet vernal or browntop. )
Some areas of tall grass can be left ungrazed for cutting for orchard mulch. At least one good cut of 'locked up' tall fescue and similar grasses can be had for mulch in late spring, and the leafy new re-growth makes good sheep feed moving into summer as ryegrass comes off its peak of productivity. This may be the last chance to have a burst of leafy sward at its best, before seed heading starts. If the sward has a good legume component, or if it had nitrogen applied in mid spring, it should grow away again strongly as a 'feed bank' for summer. Late spring is the beginning of white clovers main growing season. Ideally, it would be left to build up reserves and rebuild leaf size before it is grazing more regularly going into summer.
If the greatest amount of cocksfoot is needed for summer feed, it will grow well now if allowed to grow to 20cm at the very start of its seasonal flush (early summer). When it is grazed, it should not be taken lower than 5 cms before being left again. Kikuyu, however, needs to be grazed hard - to two leaves per tiller - if it is to maintain its leafyness and quality at this time and going into summer. Rank kikuyu has less feed value.
If red clover is being grown as an important summer feed, it will grow well now if allowed to grow to 20cm from the start of its seasonal flush in early summer. When it is grazed, it should not be taken lower than 5 cms before being left to regrow again.
But with a good chance of a dry period - and therefore a moisture deficit - in early summer, sward growth rate can easily halve. Grasses attempt to 'run to seed' starting from about mid spring, and strongly in early summer. As a consequence, in a dry early summer, the feed value of the grass that does grow starts to fall away.
If clover vigor is low in spite of good phosphate levels, apply moderate (30 gms/square metre) amounts of a potassium fertiliser. Use light to moderate applications of potassium because grass magnesium levels are often low at this time of year (anything from 20% to 50% lower than in autumn), and heavy potassium application can result in high potassium levels in the grass. These higher pasture potassium levels interfere with the sheeps ability to absorb the (already seasonally reduced) magnesium in the foliage.
If legumes are weak or few, and if no nitrogen has been put on in the previous month or so, and if soil and weather conditions are right, it would be worth applying a nitrogen dressing to accelerate production of high feed value nutritious fresh leafy growth. Avoid applying nitrogen to perennial ryegrass with 'wild type' endophytes (i.e. 'run of the mill' ryegrass cultivars were sown, not endophyte free or novel low alkaloid endophyte infected cultivars) as high nitrogen staus in ryegarss is implicated in increased risk of 'ryegrass staggers'.
Summer is a time when there is potential for large amounts of nutritious legumes (for example, summer is white clovers main season of growth and flowering, given adequate and regular rain or irrigation). But, in the absence of irrigation, the potential is only rarely realised, as erratic and insufficient rain more often than not creates a moisture deficit that halts white clover growth . Production is pretty much a function of rainfall and can vary hugely from year to year. Summer is when grasses are insistantly going to seed, and little can be done to stop them, although 'topping' the seeding sward delays it. Once seeding is 'out of their system', grasses become vegetative again, to build up reserves for next seeding season. But, as with clover, post-seeding vegetative grass growth is rain dependant. In a typical dry year there is not much growth. In a wet summer post-seeding, high quality grass growth abounds. Seeding ryegrass has particularly high levels of endophyte toxins, and may cause scouring or have neurological effects.
Lambs, being smaller, need less feed to simply maintain body weight. But for a newly weaned lamb (say 20 kgs or so) to grow well (100 grams plus increase in liveweight per day), the sward needs to be able to provide the equivalent of slightly more than the maintainance feed requirements of a 50 kg ewe. As the lamb gets bigger, its daily feed requirement for both growth and increased energy supplies for its bigger body increases. By the time it can be sold in summer or early autumn, say at 30 kg liveweight, the sward needs to be able to provide around 3 kgs to 4 kgs of fresh pasture a day to the now large lamb if it is to continue to grow even larger (it can maintain its weight without further growth on less). It can be seen that while the heavy pasture dry matter demands from the lactating ewe start to decline toward the late spring, the demands on the sward from maturing lambs are high right into summer. In fact, they are close to equivalent to the daily needs of a small ewe. If the summer is dry, the needs of the orchard and the needs of growing lambs clash.
The larger home orchardist is primarily concerned with
the trees in good shape through the dry - especially if irrigation
available. Thus, while the farmer cuts and stores the grass for
home orchardist, if a mower is available, is more concerned with
the grass to mulch the trees. Mulch is a precious commodity, and
rank spring growth, it never seems to produce enough mulch to do
trees. When there is not enough grass for both sheep and trees,
in some bales of hay for summer feed may be an answer. In any
be tempted to severly graze the sward - lower than about
3 cms and the growing points are damaged, and the autumn regrowth needed for conditioning the ewes for mating (once rains do come) will be much slower. Overgrazed summer swards tend to result in shorter and weaker grass roots, and death of the weakened suceptible grasses. Bare patches result, which, come autumn rain, become broadleaf weed patches. In severe drys, even dry resistant species such as tall fescue should be left ungrazed if possible to ensure their survival.
This is, of course, the counsel of perfection. Sheep will graze
areas very hard, while leaving other areas, such as in the shade,
merely 'nipped'. Leaving them in the paddock in the hope they will
the longer grass in the shade is futile, as they will simply take
short grass further 'down to the deck'. As the soil becomes very
their urine burns out patches. As always, dung patches will be
creating numerous islands of relatively lush grass that will not
eaten unless very hungy. The decision to move the sheep out has to
made on the balance of how much damage is being done in the sun
how much 'wasted' grass is there in the shade.
The summer post-weaning-period sward quality is critical to
sward is 'feral endophyte' perennial ryegrass or 'feral endophyte'
fescue dominant and has little clover composition, conditions are
'illthrift' due to endophyte toxicity in these grasses in the
water stress. The effect is exacerbated if summer has been wet,
ample growth, followed by a dry early autumn. Lambs heat stressed
effect of endophyte toxosis tend not to eat as much, and their
is weakened, lowering resilience and resistance to worms. They
poorly developed worm resisistance in the first year of life, and
high quality pasture to repair damage to their gut from parasites.
the time they most need to be eating good quantities of high
pasture, the endophyte effect inhibits their appetite. Little can
done about it now, but it underscores the need to incorporate
free or novel endophyte perennial ryegrass and tall fescue in the
and work on increasing the clover content.
Extending sprinkler irrigation for the orchard rows so the interow sward is also irrigated is an excellent solution if it is affordable. Irrigation is as good as early autumn rain in relieving moisture stress on endophyte containing grasses, and dramatically reduces or eliminates the risk of endophyte fungus toxicity. Failing irrigation, in exceptionally dry years, or where there is no endophyte free sward to shift the sheep onto, supplements may have to be fed.
A 25kg bale of good hay is about 80% dry matter, containing 720 megajoules of metabolisable energy (there are about 9 megajoules of metabolisable energy per kg of dry matter in good hay). As an average ewe needs roughly 10 megajoules a day to maintain its body weight, about 1.4 kg of good hay a day will meet that need. Therefore, a bale of good hay will feed one ewe for about 18 days in summer (or in winter). However, this is a large amount of dry feed for a sheep to eat (let alone a lamb), and while some breeds will eat enough hay to meet their energy needs, other breeds may not eat sufficient quantity. Sheep pellets and other concentrates are a useful supplement, as they usually have about 13 mejajoules per kilogram, but sheep usually need to be trained to accept them, and they should be fed with hay or other roughage anyway.
The strategies available to the home orchardist sheep manager are
1. Destock. Anticipating summer dry, sell or kill lambs in December or January when things are getting tough (early lambing is an advantage). If you are running old or cull ewes you will have to put the tough mutton in the freezer, or find a local agent willing to buy a very small number of low value ewes.
2. Move the sheep to a conserved pasture. You may have drives, areas around the house, a small forestry lot or similar that has some 'step - through' feed. Or you may have a moist lower pasture area that you have rested for the summer feed shortage.
3. Use supplementary feeds. Most larger home orchards aren't big enough to make hay, and have already converted it to mulch for the prime concern, the fruit trees. But hay can often be bought relatively cheaply in early summer and will do for both summer dry and winter feed shortage. Many willow shelter species are palatable to stock, and these can be trimmed for summer feed (never ever use conifer trimmings - some are lethal to stock). Odd corners - or even steep unusable faces - can be fenced off and summer and winter pod-bearing trees planted. Drought tolerant tagasaste is very nutritious, and can be grown in a hedgrow close (not too close) to fences and cut for emergency feed.
4. Sow, or encourage, more drought tolerant grasses and herbs.
When the soil is dry, the roots in the upper soil zone become inactive. Roots in deeper zones of the soil will become more active, and are able to actively take up nutrients such as phosphate if they are available at deeper levels. However, as the soil profile dries out, only the most deeply rooted grasses and legumes can continue to produce. In extended drought, only extraordinarily deep rooted lucerne and chicory are likely to remain green.
Tall fescue - very deep rooted, ideal for dry sandy or volcanic soils, can be grazed at approximately 10 day intervals, bouncing back well in between. But it's very vigor means it has to be relatively intensively grazed or it will tend to get away. Sow novel endophyte, or endophyte free varieties.
Cocksfoot - deep rooted, usually upright, but there are prostrate cultivars particulalry suited to sheep grazing
Red clover - has a tap-root, so survives drought better than white clover, and, especially if superphosphate was applied in late spring to give it a boost, continues growing where white clover closes down. Unfortuneately it is not very persistant, often fading out of a mixed sward by about the fourth year.
Chicory - selections of this herb are renowned for producing high quality sheep feed over the warmer part of the year. It can be grown alone or combined with grasses and with clover. On the minus side, it only persists for 3 to 5 years, needs some care in getting it established, and prefers a fertile, well drained soil.
Plantain - tolerates low fertility soils, but unless modern cultivars are bought, it is a semi-prostrate rosette forming plant, so it takes up a in inordinately large area relative to its feed value. New varieties are significantly more upright.
Lucerne - very productive in spite of drought, deep rooted, but subject to pests, and has to be grown and weeded as a 'pure stand' as it can be 'swamped out' by other species when rains return. Fits with phalaris quite well, as phalaris is a strong winter grower, but goes semi-dormant in summer, allowing the lucerne to take over.
If there is good summer rain, kikuyu should be mown to at least 5
if the sheep can't keep on top of the growth. On the other hand,
kikuyu very hard at this time will tend to prevent late flowering
of subterannean clover (if you are using this annual clover) from
a good seed set, which in turn means fewer plants germinating in
for winter production. The balance is preventing rankness but not
too much subterranean clover flower.
Perennial grasses will resume nutritious leafy growth once they
seeded, and the biggest problem may be an embarrassment of grass.
pasture re-growth from a mowing for mulch earlier in the year
a further useful cut for a mid summer mulch to help seal in
If there has been a dry period long enough to stress ryegrass
the rain, the rapidly growing new ryegrass may have high levels of
and mowing to reduce the problem may be advisable. In addition,
continues to build up in the soil even when the grass can't grow
drought. Once the drought breaks, the sudden growth spurt can
high nitrate levels in the foliage, even when no nitrogen
has been applied. Beware of nitrate toxicity.
If the summer has good rain white clover will grow away strongly - as long as lime and phosphates are adequate. Nitrogen applied to damp soils now will boost the growth of summer responsive grasses, but in excess, may suppress nitrogen fixation by the clover. If the soil has been well fertilised previously, and the clover is growing well, there is little need for a nitrogen application at this time beyond 'spillover' from an opportunistic light feeding of subtropical fruits.
If pasture potassium is needed and late spring/autmn split
are not being used, a heavier application can be applied once the
have been weaned (late summer), although there won't be much
unless it rains.
Fertiliser and soil types
Sand based soils are notoriously 'hungry' (and drain quickly, tending to wash some minerals through), partly because they lack clay which tends to (reversably) bind and hold minerals. Sandy soils may need regular application of potassium, perhaps as often as every other year. They are more likely to need phosphates, and more likely to run into magnesium shortages. While sandy soils don't need as much lime as heavy clays and peat soils, sandy soils can still become acid if liming is neglected, and iron (in particular) can become unavailable. (Iron deficiency will extremely rarely affect grass, but more commonly affect some fruit trees, particularly citrus.)
Clay based soils are opposite to sandy soils - they hold applied nutrients well, and drain slowly. Clays are acid soils, and need regular dressings of lime to both maintain the pH and to help formation of better structure in the soil. Where citrus are to be grown, calcium sulfate (gypsum) is probably prefable to use to dig in to assist soil structure formation, as it doesn't make the soil too alkaline.
These contain variable amounts of very fine to large coarse particle, and their mineral holding capacity is broadly somewhere in between the fine mineral clay soils and the coarse mineral sandy soils.
Volcanic ash and pumice soils
The form of clays in these soils hold and release phosphate quites well. They also store sulphates well. Sulphates are important for grass growth, so these soils are well suited to pasture, especially as they they are less prone to leaching out of minerals than some other soils. Pumice soils may have low natural levels of magnesium, and with a tendency to slowly leach magnesium. Ash soils are less likely to be low in magnesium.
The role of humus
Humus is characterised as minute, black, structureless particle, or a formless 'jelly' coating on clay, silt, or sand particles in the soil. Humus is the 'residue' of decomposition by soil organisms. Soil organisms build up complex compounds, including a dark compound of oxidised and partly decomposed 'woody' lignin from plant cell walls. This, plus dead soil organisms and structureless bits of plant residue, together form humus.
Humus has some very useful properties, but chiefly the property of 'mimicking' some of the useful properties of mica clay. Mica clays are valuable in the soil because they have a very high potassium holding and exchange capacity. Soils with poor potassium holding capacity can have it improved by the building up of organic matter, some of which ultimately becomes humus. Humus also has the ability to 'sorb' ions, and can hold and exchange bases, such as calcium. Around 50% of the humus is in the form of humic acid, which combines with basic ions applied to the soil.
Humic acid has around 5% nitrogen content. (There is, of course, far more organic matter in the soil than the final humus portion.)
Humus and clay colloids can 'capture' proteins and amino acids released from decomposing plants and animals. These captured protein sources are only slowly mineralised, as soil organisms find them difficult to release. Thus a portion - one estimate is 1% - of the organically derived soil nitrogen is constantly both stored and slowly released by humus over the course of the year.
Organic matter as a whole - rather than humus - is also involved
the storage and release of phosphates. Phosphates combine with
compounds complexed with clay and silt particles in the soil, and
complexes release the phosphate when they are attacked by soil
As much as 50% (depending on the specific properties of a given
be held in this form. As a result, most phosphates from organic
are available to plants when soil organisms are most active - in
and in autumn (and in wet summers).
A biologically active soil with
organic content depends on a variety of factors, for example, pH,
sward species, and root penetrance. Having phosphate stored in
form is far more important in soils that bind phosphates strongly
in other soils (unless its binding capacity has been fully
extremely heavy applications of phosphate).
As a broad proposition, as long as both calcium and phosphate levels are maintained, no additional fertilser is really needed on most loamy soils for sward growth sufficient for sheep. But additional fertiliser may be needed for the fruit and nut trees at key points.
How much of what fertiliser is needed
The types and uses of nitrogen has been discussed extensively above in the context of increasing sward growth.
Lime is basically calcium carbonate, which provides the constant supply of calcium for plant growth in addition to maintaining the soil pH at a range where minerals are most easily available to plants. Broadly speaking, fruit and nut trees don't need much lime, so liming to maintain the best pH for grass and clover growth also takes care of tree fruit needs. Preventing nutrient imbalance and deficiency due to soils that are too acid or too alkaline is far more important for fruit and nut trees. The best soil acidity range is the one where the greatest number of plant nutrients are readily available in the greatest amount. For fruit and nut trees this is about pH 6 to about pH 6.5. Any pH test result (small kits can be bought from garden centres) below pH 5.8 indicates the need to apply lime.
There is a fairly steep pasture productivity response to lime up
about pH 6, when unfavorable pH is no longer limiting production.
'average' soil (not markedly sandy or clayey) 2.5 tonnes of lime
hectare will shift the pH by approximately 0.5 of a unit (250
metre) in the top 75mm. (The degree of change in pH effected by
of liming is less in a clayey soil, and more - up to 1 unit - in
soils.) Sward responds readily to changes in pH in only the top
this apparently modest depth of penetration is not limiting.
to the soil surface seems effective. Only on peat soil does it
be rotary hoed in to reduce the high acidity characteristic of
as deep as possible.
Once pH 6 has been attained, regular dressings
of lime will be needed to keep the soil at this pH, because animal
nitrogen fixation by clover, and applications of urea result in an
Lime is also important in mineralising soil organic matter,
resulting in increased availability of phophate ions (in
the soil solution.
The conventional 'broadbrush' recommendation to counter this natural process is to spread about 10 kg of lime per sheep carried per hectare per year. The amount of rain and the type of soil affect the rate that should be applied. Higher rainfall areas coupled with free draining soils are likely to need heavier applications.
While some commercial sheep farmers lime a third of their sward a year (or only apply a single heavy dressing - 2.5 tonnes/hectare - every fourth or fifth year), the pH can slip out of the optimum range in the two 'off' years. Keeping within the optimum with annual applications improves the availability of minerals, maintains the earthworm population, improves root structure. This results in better growth, better nutritional value, and better drought tolerance of the sward. Pasture seems able to be kept more or less in the 'optimal' pH range on most soils with applications of around 500kgs/hectare per year (50 grams/square metre per year; half that or less for sandy soils). Paradoxically, once a soil has been brought to pH 6 and the sward improves, earthworm numbers improve, calcium moves more quickly and more deeply into the soil due to the improved drainage, and heavier dressings of lime may be needed for a while to maintain pH levels at the soil surface.
Crushed and finely ground limestone rock (28% - 38% calcium content) is cheapest, with bulk spreading much cheaper than buying 'by the bag'; but 'by the bag' is usually more convenient for the large home orchard. Very fnely ground limestone washes more quickly intot the soil, and is more active, but more transient. Liming can be done at any time of year, but winter is probably more strategic if urea is going to be used.
While most soils do not lose a great amount of phosphate from leaching in rainwater, some of the total phosphate component are permanantly immobilised ('fixed') in many soil types, so while present, a variable portion is not readily available to the plants. In addition, phosphates are gradually removed from the soil. Every sheep that is sold or killed takes with it the equivalent of about 2.5 kgs of superphosphate. A similar amount per animal per year is transferred in dung to resting camps in shady areas. But applying 5 kgs of superphosphate a year for every sheep carried will not be enough to maintain levels of plant available phosphate in the soil, let alone build soil reserves.
Soils can be
to establish their existing useful (i.e. plant available)
Soils with a low 'plant-available' phosphate level give an Olsen
test result of 9 or less. Soils with high plant-available
Olsen test at 30. However, measure of pasture yeilds with
soil phosphate levels show that an Olsen P level of 20 gives
of possible increased yield response. Some soils will reach almost
full yield increase potential at Olsen 10; most soils reach 95%
potential at Olsen 15 (15mgP/kg soil). Response
is dependant on the fixation characteristics of the particular
and possibly other factors (such as increase in aluminum on some
Superphosphate contains around about 8.5 % of phosphate available
90% of which is soluble in weak acid (2% citric acid solubility is
test of its availability in the environment of the soil). It also
11% of sulfur in the sulphate form, sulphate being essential for
growth. Overall, the product is only very slightly acid, mostly
amounts of water soluble phosphoric acid. However, if it isn't
it can create temporary acid conditions around the granules until
and washed in by rain. (It can be as low as pH 1.5 in the
which is why care has to be taken using superphosphate under
fruit trees when conditions are damp enough to dissolve, but not
Superphosphate is generally sold granulated, or in the form of a coarse to fine powder, with some unground granules still present.
Ash soils have relatively high iron and alumnium components in their clays. The very acid conditions immediately surrounding the granules of superphosphate can dissolve out some of this iron and aluminium which react with the phosphate, forming various insoluble iron and aluminum phosphate precipitates. The phosphate in these compounds is then for practical purposes permanently unavailable to plants. About 10% extra phosphates are often applied to these soils to compensate for loss from binding and precipitation. These ash soils hold stores of sulphate quite well, so reactive rock phosphate may be the cheapest phosphate where additional sulfur is not useful.
Strongly phosphate fixing soils may initially fix 70% or more of the applied phosphate. Soils with low initial phosphate levels, and which also strongly fix phosphates by forming insoluble mineral precipitates, may benefit by very heavy initial superphosphate applications to react with as much of the receptive minerals in the top soil levels as possible. This allow less of the later maintainance dressings to be locked up by reaction with these minerals. With repeated applications, a steady state is reached - some phosphate applied is fixed, but some of the existing organic phosphate reserves that have been built up are mineralised and become available for plants.
Some of the phosphate ions are adsorbed onto the surface of fine soil particles. These are relatively readily available to plants. The amount of phosphate that can be held 'adsorbed' in the soil 'bank' depends in part on the type of soil. In some soils, the types of clay minerals present allow phosphates adsorbed onto their surface to become weakly available. Soils derived from volcanic ash and pumice have 'allophane' clays which bind tightly to phosphates and only release them slowly. Old pastures that have been regularly fertilised with phosphates and have good supplies of calcium, will build their percentage of organic material in the soil to maximum levels, and these soils, even when they do not have suitable phosphate adsorbing/suppling clays, hold reasonable quantities of phosphates in the form of complex organic minerals (eg humates) in spite of fewer, or poorly effective clay particles. Phosphate ions are slowly released from these organic minerals.
Quickest availability comes from application of superphosphate. As superphosphate has converted almost all the phosphate rock into highly soluble form, it is available relatively quickly, but its reactions with soil minerals - adsorbtion or precipitation - also happens relatively quickly. Being water soluble, amounts not temporarily adsorbed by soil organic compounds and clay mineral particles can be quickly leached into lower levels. There is usually less (or no) organic material at lower levels, and the phosphate is likely to be either bound on minerals (in medium and high phosphate fixing soils), or washed through (in free draining soils with very low phosphate fixing capacity) in the ground water. Rain washs the water soluble monocalcium phosphate out of the superphosphate granules fairly readily, and while a granular shell may be visible on the soil surface for quite some time, it is 'spent', being basically calcium sulphate (gypsum).
Reactive rock phosphate, in contrast to superphosphate, is alkaline. 1 kg of reactive rock phosphate has the same 'liming value' as applying 500 grams of lime. The genuinely reactive very finely ground rock phosphates (e.g. 'Gafsa', 'Sechura', and 'Kosseir') are highly reactive, with a minimum of 30% solubility as measured by the citric acid solubility test. They contain around 10% more phosphate than superphosphate, and while their available soil phosphate levels are lower than superphosphate, they are maintained for longer at useful levels - available soil phosphate levels don't fall as quickly between applications as they do with superphosphate. This is particularly important for clover, which source almost all its phosphate from the top 75 mm of soil (where ryegrass sources about half its phosphate from this surface zone, and the rest in the next 75 mm of depth).
Superphosphate can also be 'neutralised' with lime, forming
'dicalcic phosphate'. Some commercial
sward growers prefer dicalcic phosphate, because it is a
neutral pH) form
phosphate with a high calcium content. It is created by mixing
quantities of moist crushed limestone
rock and superphosphate and leaving it to react for a month or so.
phosphate content is around 5%. Although the phosphate from
superphosphate is not water soluble, it is present in the soil at
useful levels for a shorter time compared to reactive rock
but for a longer time in comparison with superphosphate. The
content is around 24% (lime is 28-38%) and is in the form of
carbonate and calcium oxide.
Sedimentary soils, especially in higher rainfall areas, tend to
sulphate leached out of them. In this case, superphosphate, with
sulfur (prefeably applied in split dressings to minimise
an elemental sulfur blended reactive rock phosphate is more
phosphate sources, such as 'triple super' (21% phosphate) are low
but can have fine elemental sulfur added ( 2%-10%, depending on
levels). Elemental sulfur is converted to sulphate gradually, so
pace with grass requirements with minimal leaching.
'Triple super', also known as 'double super', is made by reacting
the phosphate rock with phosphoric acid, thus increasing the
phosphate content. Generally, it is useful because the same
fertilising effect can be achieved with half the weight of
This phosphate fertiliser is usually manufactured as a coarse
fairly dust-free and able to store without caking. Depending on
it may be useful for hand-spreading on steepeer faces in the
In any event, whether the soil has high phosphate fixing characteristics or low, phosphate is usually retained in the top 50mm or so of the soil, and its availability to plants decrease rather quickly. After six months, only about half the applied phosphate is available to plants. The main effect of phosphate appplied to soils that are not actually phosphate deficient is to stimulate the growth of legumes, which fix nitrogen in the soil and thus stimulate grass growth. The effect starts more or less immediately, so long as the soil is moist, there has been sufficient rain to wash the fertiliser in, there is a good percentage of legumes in the sward, and it is warm enough for legume growth. The degree of response depends on the amount applied.
Amount applied should be based on a soil test to determine the reserves present and to determine whether your soil 'fixes' phosphates weakly, strongly, or in-between. A 'broad brush' approach in the absence of a test is to apply a heavy 'capital' application far in excess of growth needs for the first few years - 1,000 kg superphosphate/hectare - then cut back to 'maintenance'. As long as the soil is not too basic, finely ground reactive rock phosphate may be the most useful phosphate source for 'maintenance' dressings. It releases its phosphate more slowly than superphosphate (via weak carbonic acid naturally present in the soil), and for a longer period of time. If the soil is known to strongly fix phosphates, very heavy dressing - 1,500 kg/hectare, or even more - are sometimes used. In soils that are known to have very low phosphate reserves to start with, and which fix phosphates strongly, extremely heavy dressings are sometimes applied - as much as 2,200 kgs/hectare.
On most soils there is a greater initial response to higher rates of applications, albeit superphosphate never gives an 'immediate' response in the way applied nitrogen does. In good growing conditions, pasture yields can double in the three months following application of high amounts (e.g. 500 kg superphosphate/hectare). A year later, a sward dressed with 500 kg superphosphate/hectare (50 grams/square metre) will still be producing about 50% more growth of pasture than a comparable sward that received nothing. But the decision to try to boost pasture growth in a particular season (winter, for example) by phosphate dressing really depends on having a good percentage of legumes in the sward, moist soil, a sufficiently high soil temperature, and plenty of 'lead' time for nitrogen levels from legume activity to build up before cool weather halts it. If conditions for response don't exist, there won't be a response until conditions change, no matter how much is applied.
Autumn is generally the best time to apply phosphates as there is some response by legumes in late autumn and early winter, then a further response in spring. New grass seedlings often show a good growth response to higher than maintainance superphosphate dressings. Spring is also a suitable time, and the soil is moist and warming rapidly.
Superphosphate can be mixed with potassium chloride, although small amounts of hydrochloric acid are released over time (potential to rot natural fibre sacks). It can be mixed with lime, although it will tend to cake over time.
Phosphate deficient grasses may have a purplish tinge.
There are two major forms of potassium fertiliser - potassium chloride and potassium sulphate. Potassium chloride is cheaper, but some fruits are intolerant of the chloride form.
Most soils have good potassium holding capacity and good potassium reserves, almost entirely in inorganic form. Soils from long term grazing land (especially where hay is made) often end up with depleted potassium reserves. There may be ample potassium reserves in the soil, but the availability to the plant depends on the characteristics of the particular soil. Sandy soils often have less potassium holding capacity. Many volcanic soils, soils derived from andesite or basalt rock, and soils with kaolin clays have a low potassium supplying power. Vermiculite-containing clays have intermediate supplying power, and mica and illite based clays have high supplying power.
Some fruits, and stone fruit in particular, have a relatively high potassium requirement, particularly when grown on light, free draining soils.
A potassium deficiency in otherwise high fertility swards
vigor. Grasses compete vigorously and successfully with clovers
soil potassium. Perennial ryegrass, for instance, accumulates
the potassium in its tissues than does white clover in the same
conditions of low potassium application. Ryegrass, in particular,
able to take up far more potassium than it needs for normal
cellular functions. It may take up the equivalent of 200
per hectare, while clover in the same pasture might take up only
Moderate rates (285
about 30 gms/square metre) of potassium will supply both grass and
needs and boost clover vigor markedly, which in turns increases
fixation, grass growth, and consequent increased competition for
soil potassium. Grasses may once again outcompete clover, and
lose vigor unless a yet higher rate (380kgs/hectare, about 40
of potassium fertiliser is applied next time.
In sheep pastures, most potassium is returned
dung and urine. Sheeps urine is a concentrated source of potassium
potassium concentration in a urine patch are at levels equivalent
heavy potassium dressing (400kgs/potassium per hectare). Urine
concentrate nutrients (potassium and nitrogen) present broady
the sward into discrete patches, and, as long as the soil is moist
phosphate not limiting, results in localised patchy areas of lush
sward. If the soil is somewhat deficient in potassium, this result
potassium being depleted outside the urine patches. Grasses
vigorously and successfully with the clover for the remaining
potassium. Ultimately, clover will weaken and may be overgrown
the potassium deficiency is corrected. If the deficiency remains
uncorrected, the species composition will tend to drift toward
low-fertility tolerant grasses.
Potassium is taken up by
grasses and legumes relatively quickly, and available soil
quite quickly over six months. Most severe competition for
is in spring, when grasses are growing most actively, and also
their flowering heads.
If hay or silage is cut and removed elsewhere, potassium levels will progressively fall in many soils - unless replaced by potassic fertiliser applications.
Excessive potassium applications can interfere with both sodium
magnesium concentration in pasture, predisposing animals to 'grass
if heavy applications are made in early spring. Early spring might
best time to apply potassium to both encourage white clover growth
to co-incide with the needs of stonefruit. But, mindful of the
the high bloat and grass staggers potential of high white clover
in spring (and the magnesium depressing effect of potassium), it
be safer to split the application into two smaller applications,
and one in late autumn.
It pays to obtain foliage analysis to determine the true potassium needs, to prevent over-application and animal health problems.
Potassium chloride can be mixed with superphosphate (although the mix will release small amounts of hydrochloric acid over time, rotting sacks made of natural fibres); with lime; with sulphate of ammonia; but not with urea (unless the mix is going to be used immediately). The salt crystals tend to absorb moisture (hygroscopic), but don't 'cake' much.
Magnesium is an important element in soil fertility and animal health. Like calcium, potassium, and sodium, it is a cation. The ratio and concentrations of these four can either work against each other to create deficiencies, or, in balance, maintain fertility and animal health. Overliming can create a 'artificial' magnesium deficiency in a soil with good magnesium reserves. Excessive potassium applications in spring can reduce plant uptake of magnesium at the very time when magnesium is critical to lactating ewes. There are various forms of magnesium fertiliser, some more broadly useful in the orchard than others.
Serpentine superphosphate is a relatively cheap source of
It has, of course, large amounts of phosphate (4 kgs of serpentine
supplies the same amount of phosphate as 3 kgs of superphosphate).
1 kg of dolomite provides as much magnesium as 3 kgs of
phosphate is needed anyway, serp-super is a cheaper option
super can also be used around citrus, which often seem prone to
magnesium deficiency. If phosphate is already well supplied,
be best (for grass sward and pip and stonefruit).
Magnesium is most likely to be 'at a premium', if not actually
in pasture in late winter and spring. 'Grass staggers'
is a common deficiency in lactating dairy animals as low spring
in the foliage clash with greatly increased demand from the
animal. Where magnesium is insufficient for the ewes needs she may
develop hypomagnesaemia, which causes agitation, convulsions, and
extreme cases, death. Magnesium reserves in the animals body are
slim, and lactating ewes need to meet the largest part of their
increased magnesium requirements from the magnesium content of the
pasture plants. Younger ewes may be able to mobilise some
from their bones, so hypomagnesaemia is most likely to affect
lactating ewes, especially those feeding multiple lambs, albeit,
general it is not
quite as quickly in lactating ewes as it is in cows, as non-dairy
demand is less. Ewes that
have been poorly fed, run down and stressed are also suceptible.
best avoided by keeping the magnesium
up, and avoiding heavy potassium and nitrogen applications at this
time. Pasture growth is not reduced until soil magnesium level
are at about 5,
even in naturally low magnesium soils, soil test is more likely to
10. But there is a difference between plants minimal needs and
availablity to the animal at peak plant growth periods.
To maintain a relatively high magnesium status in the soil to help maximise plant tissue levels, about 20 kgs of actual magnesium per hectare per year may need to be applied. This can be obtained from any of - 400 kg/hectare of serpentine super, 180 kg/hectare of dolomite, or 38 kgs/hectare of magnesium oxide. Applying magnesium fertiliser in late winter or early spring seems the best timing to maximise foliar magnesium levels at the crucial spring pasture growth period.
If magnesium is being dusted on grazed pasture or hay to treat
animals that have started to be affected by insufficient
a suitably 'animal remedy' approved brand of dolomite is the form
use. Animals rapidly excrete magnesium in their urine when there
excess to their metabolic needs (and when they are severley
they excrete none).
Calcined Magnesite - a light, coarsely granular material derived from heated magnesium carbonate rock to form an alkaline fertiliser with around 50% magnesium. Like epsom salts (a very water soluble form of magnesium sulfate) it is quickly absorbed. As it raises the soil pH, it is best not used directly under citrus - acidic magnesium sources, namely epsom salts or kieserite (another water soluble magnesium sulfate) are suitable. It is safe to use on grazed orchard sward, and is spread on pastures to prevent hypomagnesaemia (grass staggers) in sheep.
Magnesium deficiency is most obvious in citrus and in some pasture weeds. It may show as a lighter green between the darker green leaf veins, becoming yellow, and in more severe cases, reddish purple.
Minor elements - required in minute amounts
Whether micro-elements are present, or present in sufficient quantity (or excess) depends on the nature of the parent soil (primarily) and on the history of application of micronutrients. While the 'natural characteristics' of your areas soil might provide an indication - some soils are deficient in copper, for example - corrective amendments may have already been made in the past. In the case of a stone fruit orchard, relatively large amounts of copper may be in the soil due to repeated sprays with fungicidal copper compounds. Conversley, excessively high amounts of molybdenum (which can 'induce' a copper deficiency even when copper is present) may exist due to heavy use of basic slag in early years.
'Deficiency symptoms' in plants are hard to pick, and temporary response to adverse evironmental conditions such as waterlogging may mimic them. Plants may not show any deficiency symptom at all, yet there may be insufficient levels of an element - cobalt is a good example - for sheep health. Without a doubt, the best guide to the micronutrient status of your soil is obtained from laboratory analysis of foliage samples (soil samples are less reliable for a variety of reasons).
Some soils in a country might be selenium deficient, and others not. For instance, in New Zealand, only soils in most of the east coast of the South Island and parts of the volcanic plateau and Waikato are selenium deficient, most others aren't. Deficiency can be corrected by applying a dressing of superphosphate that has had selenium prills added at the appropriate rate. Selenium is required in extremely minute amounts (less than 0.1 part per million), and excess (more than 2 ppm in the feed) is toxic, so a safe option is to dose each animal with proprietary selenium 'pills' rather than treat the soil. In selenium deficient areas, typically 1.5 kg of selenium prills are added to each tonne of superphosphate (about 1.5 grams per kilogramme, or 37 grams/8 level teaspoon per 25 kg sack of super).
Zinc deficiency appears to be a problem that occurs sometimes in some fruit and nut trees, but rarely in pasture species. Most soils have adequate available zinc for pasture growth, and superphosphate contains useful amounts of zinc anyway. Zinc deficiency in citrus, stonefruit and pecans is best addresssed by repeated foliar sprays of a trace mineralised liquid fertliser containing zinc. As zinc is essential both for sheep and for plants, the regular use of a trace mineralised fertiliser (typically containing 0.02% zinc) beyond the drip line of the orchard trees will meet both plant and animal needs.
Only 5-6 ppm are required for both grass growth and stock health. Copper becomes much less available if the soil pH falls below pH 5 (as may happen on some peat soils), or if gross over-liming takes it above pH 8.5, or if the soils are naturally very high in molybdenum. At this point, it is important to correct the soil pH so the copper in the soil becomes available, rather than add more. Genuine low soil copper levels do sometimes occur, usually on very free draining sandy soils in higher rainfall areas.
Sheep are more sensitive to excess copper than other ruminants. Cases of copper poisoning in sheep have been recorded, one cause specifically linked to high intake of copper from copper-spray coated pasture under recently sprayed fruit trees, and in other instances from eating leaves of fruit trees with heavy applications of copper on them. Copper poisoning is made more likely if the sheep have eaten toxic plants, particularly ragwort, and have damaged livers as a result (the liver is an animals main 'de-toxifier'). There are also breed differences in sensitivity, with Texels noted as being more susceptible to copper poisoning than other breeds, and merinos supposedly less sensitive than other breeds. It would be sensible not to graze sheep under recently copper-sprayed fruit trees until the copper has washed off, or unless the sward is subsequently mown and left a while. (Be wary of commercial salt licks - those formulated for cattle and dairy animals may contain relatively high levels of copper.)
Molybdenum deficient soil types ( growing plants with less than 0.2 ppm molybdenum) often have a patchy distribution. Molybdenum is probably required in tiny amounts by ruminants as an integral part of the enzymes involved in waste metabolism. While minute amounts of molybdenum are also needed by plants - for example, molybdenum is absolutely essential for clover to be able to fix nitrogen (0.5 -1.0 ppm in plant tissues indicates adequate levels) - excess molybdenum (more than 20 ppm) in the sward can make copper unavailable and cause molybdenum toxicity (copper deficiency) in sheep. Where copper is naturally low in the sward, this effect cuts in earlier (when pasture molybdenum is at 8 ppm or more). It is better not to apply molybdenised superphosphate (the usual method of application) unless your soil is known to be molybdenum deficient. Applied moybdenum is strongly sorbed on most soils, and tends to accumulate with repeated applications. Once adequately supplied, further applications may not be needed. The rate commonly used is 50 grams of sodium molybdate per hectare. It is usually applied as no more than 100 kg per hectare of a superphosphate mix of 100 kgs of super plus 50 grams of sodium molybdate ('0.05% Mo Super').
Boron deficiency in pasture is relatively rare. Soil types that might develop deficiency are light, fast draining soils low in organic matter in higher rainfall areas. Available boron is mainly released from organic forms. Inorganic forms are very soluble and therefore leachable. Symptoms of boron deficiency mainly affect white clover, and appear first in young tissue. Growth is stunted or distorted, and the young clover leaflets may become purple or red. Flower, pollen, and seed production is markedly reduced. Actual deficiencies can be countered with applications of small amounts - about 2% - of borate in superphosphate. Clay based soils retain applied borate quite well, but sandy soils don't.
Over-limed soils also cause existing boron in the soil to become markedly less available. An overliming induced 'deficiency' is much more likely on sandy soils than heavier soils which have some clay component. The effect of overliming induced boron deficiency (actually lack of availability) may be greatest on shallow rooted plants, as calcium tends to be concentrated in the surface layers of the soil, and available boron is normally concentrated in the top horizons of soil. Overlimed soils will gradually have their pH lowered by urine, or applied urea.
Not required by plants (other than in minute amounts for clover nodule bacteria). Required by rumenate animals for rumen health, with sheep having the highest sensitivity to inadequate amounts. A concentration of about 1 part per million in the consumed herbage is required for sheep. It is relatively rare for soils to be deficient in this element. Some highly weathered acidic sandy soils, some pumice soils, some sedimentary yellow brown earths are most likely to be susceptible to low levels. Cobalt 'deficiency' - actually unavailibility - can be induced by overliming. Some soils with a high content of manganese oxides can 'lock up' cobalt, induce deficiency, and show little responsiveness to additional cobalt.
On soils known to be low in cobalt, and likely to leach it out due to high rainfall and free drainage, dressings of 15 to 20 grams of cobalt sulphate/hectare/per year applied in spring (when rapid growth dilutes its prescence in sward plants, and when growing lambs need it most) will usually provide adequate foliage levels over this critical period. It can be either included in superphosphate or sprayed on the pasture at the rate of 20 grams cobalt sulfate (21% elemental cobalt) per hectare. Genuinely deficient soils may need a 'capital input' of about 300 grams cobalt sulphate/hectare a year for 5 or so years, applied in superphosphate (equivalent amounts in 'prill' form are useful on very free draining soils because they do not leach away as quickly). The amount can be halved after this time. Improving the organic content of the soil may help bind cobalt in plant available form.
Applying fertiliser - integrating sward and orchard needs
The traditional advise is to apply fertiliser evenly from the trunk of orchrad trees to about a metre beyond the extent of the branches ('drip line). This more or less co-incides with the extent of the roots. As a result, the sward under the trees and between the rows is largely 'fed' by the nutrients intended for the trees. This is a major reason why commercial growers spray out the grass under their trees - they want the nutrients to feed the fruit, not the sward.
Applying 'set' rates of fertiliser without knowing the nutrient status of the soil could be wasteful when soil reserves are already ample; or could be too low where a soil is markedly low in a nutrient to start with. Being guided by laboratory soil and leaf analysis is best if you can afford it. It is usually one step too far for most home orchardists. Traditional 'one size fits all' recommendations of 150 to 350 grams of a Nitrogen:Phosphate:Kalium ( = Potassium) mix of around 5:5:5 per well established tree for each year of growth and with a maximum of 3 - 4 kilogrammes for any one tree is a useful 'rough guide'; albeit slanted to full size pip and stonefruit, and far too generous for some trees on dwarfing rootstocks.
The conventional wisdom says highly productive deep and moist soils sown in highly fertiliser responsive grass species should have Olsen tests of 25-30 to maximise grass productivity. Drier and 'thinner' soils such as on hills can only support hardier but less fertiliser-responsive grasses which will be producing near their genetic potential, (within the constrained soil limitations of poorer soil types) when phospate levels give an Olsen test result of around 18. Sheep farmers trying to reach a 'high plateau' of phosphate reserves in the soil apply as much as 400kg of superphosphate per hectare per year until the target level is reached. The rough expectation is that 400kgs will increase the Olsen test measure by 4 units over the original base line measure.
Side dressing nitrogen using urea
Urea is a concentrated source of nitrogen, the cheapest form to buy, and is easy to handle and apply. But unless it is put onto a moist soil and is 'rained in' soon after application, part of the nitrogen is converted to ammonia and volatised to the air. Even in the best conditions of rainfall and soil moisture, as much as 5% of the nitrogen can be lost within a day through volatisation, although the rate falls steeply after that, with little being lost after 4 days. An additional about 10% of the nitrogen will typically be lost by leaching, for a total loss of about 15% or so of the nitrogen content.
Light rain (4 mm or less) or heavy dew is insufficient to wash the urea in, and, if it is warm, causes greater volatisation losses than if there no rain at all. Up to 40% of the nitrogen content of the urea can be volatised as ammonia from the moist urea that is on and near the soil surface.
Conversely, under conditions of warmth and fairly heavy and persistant rain in free draining soils, as much as 25% of the nitrogen applied (especially when applications are heavy) can be lost to the ground water as it is converted in the soil to soluble nitrate.
Urea in high concentrations tends to inhibit clover under the trees, which is a good thing if you intend to spray out under the trees before summer. (Clover is hard to kill due to its water repellant leaves - larger than normal amounts of surfactant 'spreader stickers' have to be used).
There is some evidence that heavy urea use will effectively halt nitrogen fixation in clover. Once clover loses effectiveness and vigor, urea may be required to keep grass growing. Increased urea use may further decrease clover nitrogen fixation, and with excessive use, a spiral set in to the point that grass growth is largely urea-dependant rather than legume dependant.
Urea has an acidifying affect on the soil, which suits citrus and pinenuts.
Sward grasses and herbs
(Orchard Grass) Dactylis glomerata
A tall, dull blue-green leaved, tuft forming, perennial grass that is deep-rooted (around 1.7 metres, depending on soil type), thus adapted to dry-land conditions and able to withstand root feeding grub damage. Cocksfoot has a long history as a dry-land grass, and is known for its relative drought-tolerance and the ability of some cultivars to produce leaf in drier summer as well as in cooler winter conditions. Its most rapid growth is in early spring and in autumn. It tolerates light shade, making it particularly suitable for orchard inter-rows. It grows on all soil types, is productive under wide climatic conditions, and tolerates grazing reasonably well, regrowing quickly if well managed. In fact, like most clump forming grasses, it needs to be kept grazed to ensure large numbers of nutritious young leaves are continually being produced, so long as it is grazed no lower than about 4 cm.. When sown thickly and kept grazed it forms an even sward, partly through continued production of tillers throughout the growing season; but low plant numbers in a sward that is badly managed can result in stemmy over-mature clumps amongst the shorter grasses and legumes. Many summer active cultivars have a raised crown, and can be killed if grazed too hard at this time. Cocksfoot is nitrogen responsive. Well established cocksfoot swards have more than doubled their production when high rates of nitrogen (300kgN/hectare) were applied.
Of the improved cultivars, 'Grasslands Wana' and 'Tekapo' are probably best for a sheep grazed orchard sward because they have prostrate rather than upright growth, are densely tillered, and vigorous, and consequently tolerate close grazing reasonably well. 'Tekapo' is suceptible to leaf diseases, so may not be as suitable in humid areas. 'Grasslands Vision' is semi-erect (one parent is the erect cultivar 'Kara') is open enough to allow other grasses and larger clovers to grow well, and has good winter activity. 'Ella' is summer active, and is finer leaved and non clump-forming.
Cocksfoot grows well with clovers, especially if autumn sown - its slow growth allows white clover to establish well. Sowing in autumn with subterranean clover allows the sub clover to establish very well, as it is a cool season active clover, resulting in a relatively large percentage - up to 35% - of the sward being sub clover by springtime. The sub clover becomes dormant by summer, whereas cocksfoot remains active. Strong early spring clover growth means additional nitrogen fixation - important for maintaining the palatability of cocksfoot. Cocksfoot also grows well with tall fescue, perennial ryegrass, and phalaris.
Cocksfoot is slow to establish relative to ryegrass (ryegrass seedlings are twice the size of cocksfoot seedlings sown at the same time by six months from sowing), so should be sown seperately; or, if sown with ryegrass, grazed lightly but frequently to keep the ryegrass seedlings in check. Cocksfoot is best sown while the weather is still warm in early autumn, or in spring. Although cocksfoot usually germinates and grows well, adequate soil moisture and relative freedom from weeds and more vigorous grasses is the prime determinant of success. Thereafter, it should ideally only be grazed lightly over its first spring/summer (if spring sown) to allow the young plants to establish well. It should be fully established by about 12 months from a spring sowing given adequate summer moisture. The seed is small, so shouldn't be sown deeper than 1 cm.
Perennial Ryegrass Lolium
A smaller, glossy, smooth leafed grass with non-branched flower heads. Basically a cool climate plant, the main growth period is autumn and spring, and with a useful winter growth in response to nitrogen applied in late autumn. It is one of the most valuable winter grasses not only because it actively grows in cold conditions - albeit at a lower rate - but it recovers well from treading in winters cold boggy conditions. Growth is not very good in summer (and some varieties may become somewhat toxic under certain conditions) and even with summer rain, high temperatures inhibit its growth. However, ryegrass still persists under dry conditions, even if it doesn't grow. Perennial ryegrass bounces back quickly in autumns wet warm conditions. It has high feed value, being low in fibre and high in carbohydrates relative to other grasses, but must be kept well grazed in spring to maintain this quality. While widely adapted to soil type, this grass does best on heavier soils, so long as they are not waterlogged for long periods. It can 'run out' in drier areas, and is best suited to areas with summer rainfall. It is easy to establish in winter, and the seed is relatively cheap.
fescue, perennial ryegrass often contains a fungus called
within its tissues (and perpetuated from the fungus moving into
seed). Not all cultivars are affected. Of those cultivars that are
affected, the degree
of infected seed may vary from a low of 25% to a high of 70%. When
the endophyte is concentrated at the base of the plant and in the
head. There are various strains of the endophyte fungus which can
ryegrass cultivars. Cultivars with the 'wild' or 'feral' strains
endophyte fungus resist attacks from Argentine stem weevil, black
and other root and stem chewing and sucking insect pests. But the
effect is from one or more of three toxins (alkaloids -
B, peramine, and ergovaline) produced in variable amounts
the natural variability of the various 'strains' of wild fungus.
B toxin may cause 'ryegrass staggers', especially leafy grass
by a wet spring and early summer becoming water stressed in dry
and early autumn conditions and where it is 'undiluted' by
amounts of other grasses, herbs and clover.
Ergovaline effects are
associated with tall fescue rather
but this may be because they are lost in the more dramatic
ryegrass staggers. Ergovaline is produced when plants are either
stressed, or there is high nitrogen concentration in the plant.
may reduce animal growth due to heat stress, shade seeking, and
feeding. In high concentrations it affects the neuromotor system,
stiff gait and apparent lameness, and even rigid tetany and
down if the sheep are put
under stress. Most animals fully recover once taken off the toxic
but some sheep, especially lambs, may lose their resilience to
their weakened state, compounding their ill thrift. The
toxic endophyte is high when the grass is seeding in summer, so
from seeding ryegrass can be as toxic as the fresh green leaf
safer, as the fermentation helps break down the toxin).
Peramine has no apparent negative effect on animal health.
(also known as 'festucine', as it has also been found in tall
been found in some annual ryegrass cultivars, but not yet in
ryegrass. It has also been found in some meadow fescue strains.
endophyte which produces loline (Neotyphodium uncinatum) will
ultimately be introduced into ryegrass cultivars under the novel
endophyte designation 'U2'. This alkaloid is in higher
in autumn and winter, a time when some important subterannean
root eating grubs are most active.
In a 'low input' orchard sward situation, there is no good
for using ryegrass cultivars whose endophyte status is unknown,
might contain antinutritional strains of feral endophyte. Unless
otherwise, ryegrass contains endophyte.
'Low endophyte' cultivars, for example 'Grasslands Nui', have less than 25% of seeds with feral endophyte infection. While the ryegrass won't cause ryegrass staggers, it has little protection against insect damage. Low endophyte ryegrasses are best used where summers are relatively moist and insect damage less serious.
'Endophyte free' cultivars have less than 5% of seeds with feral endophyte present. Grazing trials have shown that, in summer, sheep have a very strong preference for endophyte free ryegrass over ryegrass with feral endophyte. No endophyte ryegrasses are also best used where summers are relatively moist and insect damage less serious.
'Novel endophyte' strains also have almost no toxin, but do
to insect feeding, the response varying with the strain of novel
and the cultivar. Because of the great animal health advantage,
are invariably coded with their novel type code, or with a
AR1 endophyte only produces peramine, inhibiting
feeding insects (except black beetle). This is the safest novel
as peramine is not known to be associated with any negative animal
effect. An advantage of AR1 infected ryegrass cultivars is
stock are more likely to eat the seed stem, helping keep the grass
AR5 and AR6 endophytes have both peramine and ergovaline, and
resist all insect pests, including black beetle, but have no
(and thus no grass staggers, but may have vasoconstriction effects
AR37 released in 2006, this latest endophyte seems to help
ryegrasses develop a better rootsystem (relative to other AR
endophytes), improving persistance in difficult conditions, and
increasing growth in good coditions. It gives protection against
aphid, porina catipillar and some protection from black beetle.
insect repelling compounds produced by AR37 haven't been clearly
identified. AR#& does not produce peramine. The insect
compounds might be janthitrems, only very mildly 'tremorgenic',
then only in very adverse conditions of stress on the plant.
NEA2 endophyte has all three toxins, but the levels of
B is much reduced.
Novel endophyte-containing cultivars are
where the soil dries out badly, exacerbating insect damage.
the seed dies out over time in common storage. Therefore, only
or seed stored at 5 degrees celsius or less, should be bought.
harvest date with the merchant. Merchants may code seed containing
endophyte as HE (high endophyte), SE (standard endophyte), WE
endophyte), or WT (wild type). If it has no code it can be asumed
contain wild endophyte.
Winter and early spring active cultivars generally are the first
seed in late spring and summer. Cultivars for warm temperate areas
'Bronsyn' - noted for its superior autumn growth and better summer growth (if in association with novel endophyte) than most perennial ryegrass cultivars. It flowers about mid spring.
'Meridian' - an early flowering cultivar, (several weeks earlier than 'Bronsyn') noted for strong growth in its pre-flowering period of late winter and early spring. While it loses ME earlier in spring than other standard spring cultivars, quality can be held for longer by heavy grazing or topping with a mower. This cultivar may be particularly useful for supporting the large nutritional requirements of winter lactating ewes of those sheep breeds that drop their lambs in autumn.
'Extreme' - very low aftermath heading, densely tillered, good summer quality.
'Grazmore' - a tetraploid perennial ryegrass that is very late to flower, and is better adapted to heat and drought than most cultivars.
'Aries' - broadly adapted, low aftermath heading, good summer quality.
'Commando' - a very high yeilding cultivar primarily with improved rust resistance and with better tolerance of hot summer temperatures bred for high yield in warmer, humid areas with mild winter conditions. It is primarily a highly responsive ryegrass suited to intensive production and better soil fertility.
'One50' - bred from north-west Spanish lineages and rust and pest tolerant northern New Zealand strains, this cultivar is noted for exceptional high total production and for late heading, making it particularly useful in summer and autumn.
'Hillary' - improved summer dry tolerance in a finer-leaved, densely tillered plant that does not require high fertility to grow well. It is noted for its grazing tolerance, and as a result makes a good long term pasture.
'Samson' is derived from persistant, disease tolerant old ryegrass pastures across New Zealand, and is noted for its broad adaptability and long term persistance as a permanant pasture even in more difficult environments.
'High sugar ryegrass' - there are a range of cultivars which carry a gene for increased sugar production in cool weather. The gene was found in ryegrass in the Swiss Alps, and the extra sugars help the ryegrass resist cold snowy conditions. These ryegrasses perform as well as any other grasses, but in conditions of cold nights and relatively warm days they have a higher leaf sugar content than othe cultivars. As a result, in spring and autumn, animals retain more protein from the feed, and excrete less nitrogen. The high sugar series have also been bred for extra leafiness. The performance of the sugar gene in warm temperate conditions has not yet been assessed.
Ryegrass seed is relatively large, so can be sown a little deeper than other grass species, but no deeper than 20mm. New ryegrass swards should be left ungrazed until it is well enough established it won't pull out when grazed - about 6 to 8 weeks, when, under conditions of good fertility, it will be 25 to 30 cms high. Even then, it should be lightly grazed. At this stage it has 3 or 4 leaves per tiller, and the light trim encourages it to form more new side tillers from the base of the plant. Well established ryegrass can be grazed when 100 mm or more high, but never grazed lower than about 30 mm. Some scientists suggest a good guide is to recommence grazing only when there are three fully expanded leaves per tiller. At this stage, carbohydrate reserves in the leaf should be restored, and root reserves are no longer being compromised.
Italian hybrid ryegrass
These hybrids ryegrass cultivars usually contain a higher percentage of Italian ryegrass parentage than perennial ryegrass. They are more persistant than Italian ryegrass cultivars and grow almost as much winter feed. They are not as persistant as some perennial ryegrass cultivars. 'Impact' is a fine leafed variety with better persistance (due to relatively low introgression of annual parentage), very good winter growth, and delayed - late spring - flowering (several weeks later than most perennial ryegrass cultivars), meaning high quality spring and early summer growth for lactating ewes and growing lambs.
Italian ryegrass (Annual
perenne ssp. multiflorum
A subspecies of perennial ryegrass, it has at least 10 florets on each spikelet of the flowering head, differentiating it from perennial ryegrass, which has fewer. Its leaves are a little larger and coarser than perennial ryegrass. Italian ryegrass is an important form of annual ryegrass ('Italian' ryegrass is also called simply 'annual' ryegrass), and it is distinguished by the important attribute of behaving like a biennial or a short-lived perennial. . In contrast to some other annual ryegrass forms, it can be sown or overseeded in early spring without risk of it running out to seed. It then continues to grow vigorously over the subsequent winter and early spring when feed is short, before finally flowering and running out in the second year. Autumn sowings will also last two years in warm areas. There are tetraploid varieties which are noted for very fast establishment, and normal diploid varieties. "Flanker' is a fast establishing winter active cultivar, 'Barextra' is a rust resistant, high yeiling tetraploid cultivar with good persistance. 'Tabu' is very fast to establish and has very high spring yeilds.
Annual ryegrass (Westerwold
perenne ssp. multiflorum
Another form of the annual version of Lolium perenne, the Westerwold annual ryegrasses, are noted for their rapid establishment within a sward, which gives high productivity in the season of planting. It is usually overseeded into the sward in autumn, as spring overseedings almost invariably flower and run out by winter.
fescue hybrids Festulolium (Lolium perenne ssp.
pratensis and Festuca
These relatively recent inter-generic hybrids between the genera Lolium and Festuca capitalise on the disease resistance and palatability of Festuca, and the very good grow rates of Lolium. The most sucessful cultivars have been 'back bred' so that they look and perform like perennial ryegrass, but retain the desirable meadow fescue traits. Best cultivars are strongly persistant across many soil types (as persistant as the most persistant perennial ryegrasses such as 'Impact' and 'Bronsyn'). Most cultivars follow the perennial ryegrass pattern of rising growth rate from mid winter, peaking in spring, and slowly declining into summer with summer seed head formation and drier weather. Some cultivars have a very quick summer rain growth response (relative to ryegrass), presumably due to the meadow fescue influence, and head 3 weeks later than standard perennial ryegrass. These growth attributes, coupled with resistance to leaf area being degraded by ryegrass rust, means that higher dry matter and metabolisable energy per hectare can be produced. These cultivars can be assumed to contain wild endophyte unless stated otherwise. The cultivar 'Matrix' is claimed by its breeders to grow 13,000 kgs more dry matter per hectare per year (an additional 1.3 kgs per square metre per year). The resistance to crown rust (one of the most damaging foliar diseases in Italian ryegrass) may be very useful to orchards in humid areas. Other cultivars include 'Agula', 'Felopa', 'Hycor', 'Rakopan', 'Revolution' and 'Sulino'. Some of these cultivars are available with novel endophytes.
Tall Fescue Festuca
A tall, clump forming grass, somewhat similar in appearance to ryegrass with a slightly glossy leaf undersurface (dull on top), with a loose, branched, seed panicle. In exceptional conditions this perennial grass will grow up to 1.8 metres high if left ungrazed, although it more usually grows to about 1 metre or so. It tends to grow in discrete clumps which develop tillers from basal buds when exposed to the light (by grazing or cutting). This grass is somewhat unpalatable due to rather rough edged leaves with high lignin content - although strong browsing breeds of sheep probably aren't put off. Tall fescue has a deep root system that allows it to survive and grow in soils that dry out very badly in summer. It is a little less drought tolerant than cocksfoot. While it is tolerant of low soil pH and relatively low fertility, it is a grass that responds very well to good fertility. Some of the newest varieties really only meet their high productive potential on heavier soils with relatively high inputs of fertiliser.
It will continue to grow for far longer as conditions become dry - continuing to grow when ryegrass has stopped - and 'bounces back' from drought more quickly than most. It also tolerates waterlogged conditions better than other pasture grasses. Tall fescue is one of the first grasses to start into growth in spring, at which time it is very leafy and palatable. In average years tall fescue will produce green leaf throughout summer, and newer varieties out-produce ryegrass in the critical summer and winter period. It grows strongly in autumn. Some trials have shown better animal weight gain in summer using improved tall fescue cultivars compared with ryegrass. It is both persistant and grazing tolerant.
Its deep roots helps it tolerate root feeding grub attack better
most grasses, and varieties with novel endophytes (low or no
are maintaining insect protection while minimising the negative
(heat stress etc) from the naturally occurring alkaloid-producing
(Neotyphodium coenophialum) that affects many cultivars of
grass. Alkaloid toxicity - chiefly ergovaline - is associated with
stress, or with high nitrogen concentration in the soil. (The
peramine and loline are also found in tall fescue, but no effect
has been documented yet). The alkaloids are found mainly in the
the plant, and 'antinutritive concentrations' are usually
the summer or autumn season, and only some seasons (depending on
and soil conditions). Tall fescue swards infected with 'wild type'
fungi are also less palatable to sheep than swards made up of
that are endophyte free or infected with novel endophyte.
Cultivars that are free of all endophyte may die out after only 3
so years in areas where root feeding insects are prevalent.
Mature tall fescue is not a very palatable grass, but palatability is improved in the new cultivars (e.g.‘Grasslands Roa’ and its succesor 'Advance', 'Barolex' and 'Dovey' ), with some being more palatable than others. New low toxicity 'novel endophyte' strains are almost as palatable as endophyte free strains, but retain the advantage of insect resistance.
Many cultivars have been 'cleaned' of their toxic endophyte fungi
are available as endophyte free (e.g. 'Dovey'). Newer varieties
'Vulcan' and 'Jesup' are available endophyte free. Some very old
endophyte infected varieties, such as 'Kentucky-31', are now also
in endophyte free versions. Some varieties are available either as
free or with novel endophyte, e.g. both "Quantum' and 'Jesup' are
available with no endophyte and are also available with the
endophyte MaxQTM. Some new
'ArkPlus' are available only with
Cultivars with the novel endophyte MaxPTM gives
(as do all endophytes) that may result in a greater than 20%
in pasture production. MaxPTM,
wild endophytes, has no obvious negative animal health effects.
There is no good reason not to grow endophyte free or novel endophyte tall fescue; there are compelling reasons not to grow tall fescue whose endophyte status isn't known.
Those upright cultivars with relatively tough leaves such as 'Dovey' and 'Au Triumph' withstand heat, dry conditions, and lower fertility better than the more palatable low-lignin soft leaf cultivars such as 'Advance' and 'Vulcan'. On the other hand, some soft leaf cultivars such as 'Barolex' have a higher annualised pasture dry matter content per hectare, partly due to their later flowering characteristic, and in the case of 'Advance', partly due to increased rust resistance. Some cultivars, e.g. 'Advance' and 'Vulcan', have strong spring, summer, and autumn production, but are winter dormant.
There are also cultivars adapted to mediterranean type climates (e.g. 'Flecha', 'Resolute'), but many of these types show strong summer dormancy. They produce well in winter and spring, but so does ryegrass, so their advantage is unclear.
Early autumn is the best time to establish this grass. It is slow to establish (although 'Advance' and 'Dovey' have high seedling vigor), and the moist relatively warm conditions of early autumn allow it to become well established before growth slows right down in winter. It can be sown in late winter or early spring, but is more likely to fail in a dry summer. As it is a 'bunch' grass, very lightly grazing once the seedlings reach better than 100 mms height promotes tillering from the basal bud. The grass should not be grazed lower than at least 75 mm high in the first year, but mown or grazed if it gets to 250 mm. Reducing excessive height allows sunlight to stimulate the basal buds to produce more tillers, helping close the sward. Once well established, the sward can be grazed down to 50 mm if soil fertility is good and the soil not too drought prone. Grazing to no lower than 75 mm is better if the soil is very free draining and light.
Clover grows well with tall fescue, and could be mixed in with the tall fescue seed at the time of sowing. This is particulalry important for varieties with 'wild type' endophyte, as clovers - or other grasses - help dilute the amount of alkaloid the sheep ingest. Sowing mixed in with ryegrass seed is not recommended because ryegrass is so fast to establish it out-competes the germinating tall fescue and suppresses it. Tall fescue establishs well when slower establishing grasses such as cocksfoot and phalaris are included in the mix, and also grows well with chicory.
Meadow fescue Festuca
A perennial clumping and tillering 'bunch grass', not as much used as tall fescue, but much more palatable, and will be preferentially grazed by sheep. It is slow to establish, but in the best cultivars its production rate is similar to ryegrass, and on better soils its summer production is superior. The wild plant is widely adapted to soil type, drought, wet soils, and can be disease tolerant. So far, cultivars have tended to be selected for specific local conditions in Europe and Canada, and are not as widely adapted. Wild strains in some countries have all but disappeared due to strong stock preference and slow regrowth from grazing. Cultivars include 'Barbarossa', 'Barkas', 'Ensign', 'Festina', 'Mimer', 'Pradel', S-215' and Sturdy'.
Timothy Phleum pratense
A dull green perennial grass tolerating wet, heavier and peaty soils. Timothy doesn't starts growth until mid spring, which means it flowers much later than most cultivars of major sward species such as ryegrass. The advantage of timothy is that it is highly palatable at the seed head stage, and as a result it makes high quality hay. The disadvantage of timothy as a sward grass is that it is intolerant to drought, it has no resistance to Argentine stem weevil, and, except for a few cultivars, is intolerant of grazing, being slow to recover. It is also slow to establish. Improved persistant, late flowering cultivars that better tolerate grazing include 'Grasslands Kahu’, 'Charleton' and 'Barleza'. The seed is very fine and shouldn't be covered too deeply.
This is a deep rooted (around 2 metres) and an exceptionally drought tolerant perennial grass, surviving even severe droughts (paradoxically, it also withstands waterlogging very well). Surviving doesn't mean growth - it is able to survive extreme drought by becoming semi-dormant after seeding and making barely any growth until late summer or early autumn rains. If summer rains do comes, it does have the ability to make modest amounts of growth.
It is a productive winter grass, producing about twice as much as ryegrass at this time, and its main flush is, like most pasture species, spring and autumn. Like tall fescue, it will not tolerate constant rounds of close grazing. A minimum ungrazed residual height of 75mm should be left after grazing. The spring growth may need to be topped to about 10 cms to keep it vegetative. It should not be heavily grazed immediately prior to summer (i.e. 'spell' phalaris dominant swards in late spring). The ability of well established phalaris to spread into bare areas in the sward is useful in keeping the sward 'tight'. Phalaris is noted as being exceptionally resistant to grass grub and other insect pests of pasture plants. This resistance may, in part, be due to the prescence of indole alkaloids in the plant. These may reach levels high enough to be toxic to stock at certain times - after a drought, for instance. These alkaloids affect the central nervous system, and cause tremors and staggering, or sudden death. Symptoms appear as the alkaloids accumulate, and this in turn depends on the level of toxicity, the amount of phalaris in the sward, and the time spent grazing it. In extreme instances, symptoms can appear in days, or it may even take months. There are, however, low alkaloid cultivars available (e.g. 'Grasslands Maru', 'Holdfast', 'Maraton', 'Palaton', 'Venture', 'Perla' and 'Sirosa' - this last cultivar is a selection of a North African species). Under extreme conditions, even low alkaloid cultivars may cause toxicity. As cobalt assists breakdown of the toxin in the rumen, low cobalt levels may predispose animals to the toxins affect.
Because of the potential for toxicity at certain times, phalaris is never grown as a pure phalaris sward, it is mixed with other dry-tolerant, strong winter grasses such as cocksfoot and tall fescue. Phalaris grows well with clover (once well established), and its semidormancy in summer helps clover to survive this high stress period. It needs a warm soil to germinate, is slow to establish, the seedlings have low vigor, and are easily out-competed by more vigorous species. Although widely adapted to soil types and tolerant of low pH, it performs best on heavier, more fertile soils. Phalaris is a persistant species in the sward.
Prairie Grass Bromus
A drought tolerant annual or perennial 'clump forming' species that grows up to a metre tall. It is not as free tillering as some other clump forming grasses. It has glabrous leaves, and a large, open, drooping flower spike and relatively large seeds in a slightly flattened spikelet. It re-seeds freely so long as it is not grazed too heavily early in the growing season. It not only withstands drought (it is semi-dormant in summer), recovering very well in autumn, it also produces very good winter feed (of a quality comparable to perennial ryegrass) so long as it is well supplied with nitrogen, to which it is very responsive. Its annualised productivity is usually greater than ryegrass. Spring regrowth is particularly high in water soluble carbohydrate (over 12% on a dry weight basis). This is a valuable attribute in helping to reduce the danger of bloat caused by high protein/low carbohydrate grass which is the norm at this time of year. Its magnesium content in spring is lower than ryegrass when grazed hard. Although prairie grass is valuable for its winter growth, high winter feed value (better than 10 MJoules per kg of dry matter of metabolisable energy) and year round feed quality, it is somewhat difficult to manage. Prairie grass withstands quite hard grazing in the cooler part of the year, but, as it is a 'joint grass' whose growing point is elevated as it enters the reproductive phase in spring, it can be badly set back if it is grazed at this time. For greatest persistance and self re-seeding in autumn, it is best left ungrazed until it has regrown three leaves per tiller. It is more resistant to root feeding grubs than ryegrass. It is adapted to free draining soils, and simply will not survive on heavy soils. It is intolerant of heavy trampling when the soil is wet. Unless it is allowed to reseed, like ryegrass, it does not persist in the sward for longer than about seven years. Improved cultivars are 'Grasslands Matua' and 'Lakota'. Sowing is normally done in autumn or in spring when the soil is warm. It is slow to establish, and competes poorly with other vigorous grasses at the seedling stage.
Yorkshire fog (Velvet grass) Holcus
An adaptable, vigorous, mat forming grass from Portugal (not Yorkshire) with soft velvety leaves, doing particularly well in damp situations, and whose main production period is late autumn, winter and spring. Ungrazed, it will grow 50 cm or more. Yorkshire fog grows on a wide range of soil types. If well fertilised it grows well over winter (producing a little less than ryegrass), but it is usually suppressed by sheep selectively grazing new growth very hard. It is one of the first grasses to become active in spring. Later in spring, it tends to produce large amounts of leaf litter, which may create good conditions for the fungus that causes facial eczema in sheep under warm damp conditions. This litter persists into summer and early autumn, when better re-growth prior to winter then obscures it. It can spread vegetatively by forming roots at the nodes when shoots are prostrate on the ground. These newly rooted shoots can form a 'mop' of profuse new tillers. If allowed to flower, it seeds prolifically. Ungrazed swards mature seed from early in mid summer on. It is not very summer active. Most seed is immediately viable, but a small percentage of seed can remain dormant deeper in the soil for up to ten years. As long as it is kept well grazed the young leaves are very palatable to sheep. Rank mature growth, however, is unpalatable. An improved cultivar is ‘Massey Basyn’.
Soft Brome, Goosegrass Bromus
(syn. Bromus mollis)
An erect annual spring-flowering grass growing to 80cm tall. Soft brome has flat, hairy leaves, and a dense flowering panicle about10cm long. Soft brome prefers moist areas. An improved cultivar is ‘WT Whatawhata’.
Browntop Agrostis capillaris
A fine grass with underground rhizomes, it is often regarded as a grass of poorer, heavier soils. It forms delicate feathery flower heads in summer about 45 cms high. When closely grazed by sheep it forms an almost lawn-like sward, so long as summer rain is sufficient. An improved cultivar is ‘Grasslands Egmont’.
Sweet Vernal Anthoxanthum
Much liked by sheep, this sweet smelling, shallow rooting perennial grass does well in a permanent sward, starting into growth early and is one of the first to flower, flushing and flowering in early to mid spring. Seed matures in ungrazed swards from early summer on. Although shallow rooting, it is persistant, tillering profusely, but is not greatly productive, carrying only three or so leaves per shoot. Sweet vernal is well adapted to surviving in low fertility swards; but productivity is much improved with fertiliser. It does not persist in very wet soils. Sweet vernal smells sweet due to the prescence of 'coumarin' a harmless fragrant phytochemical. Hay composed largely of sweet vernal can become dangerous if it becomes damp and mouldy. Common mould fungi convert coumarin to dicoumarol, a vitamin K antagonist, which can result in internal bleeding. ‘Grasslands BZ 2330’ is an improved cultivar.
Annual Poa (Annual bluegrass) Poa
A relatively small but vigorous annual that seeds whenever conditions of growth are good. It produces dense, fine leaves, mainly in spring. This grass is a rapid colonizer of bare areas, and grows well in the shade of shelter belts. It grows fairly well in summer, and is palatable, but flowers early in spring. It will flower at a height of only 4 cms, so is hard to keep vegetative.
Kikuyu Pennisetum clandestinum
A vigorous, drought tolerant, prostrate perennial which forms dense stoloniferous turf. In warm and moist conditions it spreads vigorously above and below ground (via rhizhomes). The rhizomes penetrate about the top 60 cms of soil, and a few roots may penetrate to about 5 metres deep. The short, leafy branches produced by actively growing stolons have a high protein content, and are both highly palatable to sheep and highly digestible (new growth is better than 70% digestible). It has to be grazed much harder than other swards to keep it short (about 2 cm) and at its most leafy and nutritious. Kikuyu also has the advantage of being responsive to nitrogen fertiliser, and providing feed in dry summers; but it has the distinct disadvantage of browning off if frosted in winter - and growing exceedingly slowly even if unfrosted. This can be compensated for by oversowing with white or subterranean clover, which will grow well with kikuyu and provide winter feed - so long as the kikuyu it is kept closely grazed (and so long as there is ample phosphate for the clover). If conditions in autumn are right (heavy rain and moist soil) annual ryegrass can be sown into a very hard grazed or severely mown kikuyu sward for additional winter and early spring feed.
Kikuyu responds so vigorously to wet summers that it will almost certainly need to be mowed to prevent it overgrowing and suppressing the clover. Its ability to travel under the soil and rob moisture in dry weather means it is undesirable anywhere near fibrous and shallow rooted fruit trees.
Kentucky Blue Grass
Meadow Grass) Poa pratensis
A relatively low growing, dense 'sod forming', perennial, cool season grass with smooth stems. It has the virtue of spreading laterally to fill in open areas due to its rhizomatous nature, and is persistant even when overgrazed. It is palatable, tolerates heavy grazing, but becomes semi dormant in dry summers. Relative to most grasses, it produces poorly. White clover grows well with Kentucky blue grass as it is not so severely shaded compared to other cool season grasses. It tolerates dry and relatively infertile sites well, but is intolerant of waterlogging.
Smooth Brome Bromus inermis
A productive sod-forming species notable for its hardiness and relative drought tolerance. Because it has an elevated growing point, it is rather intolerant of close grazing, requiring long intervals to recover, which limits its usefulness as a component of the sheep sward .
Weeping rice grass Microlaena
A creeping grass native to Australasia that tolerates some shade and tolerates drier conditions. More drought tolerant than cocksfoot. The cultivar 'Shannon' is available in Australia.
Chicory Cichorium intybus
A deep-rooted, drought-tolerant perennial herb valuable for its palatable high-quality (10-30% crude protein, depending on growth stage) leafy summer feed (of 70-80% digestibility) produced in large quantity from its crown as long as soil moisture is adequate. It also produces very well in autumn. Quality declines if the plants are allowed to start to form their tall flower heads in late spring. (If it is not grazed hard enough at this time, regrow tends to be from leaf buds on the flower stem instead of the crown.) Relative to other sward species, chicory contains relatively high levels of potassium, calcium, magnesium, sulphur, zinc, iron, copper and sodium. It grows well on most soils and its large tap-root has an outstanding ability to penetrate compacted subsoil to access moisture at deeper levels, able to attain depths of 75 cms after only one seasons growth, and, at maturity, 1.3 metres. It only persists for 3-5 years and is winter-dormant, persisting as a low rosette of leaves. It can be incorporated into a grass-clover sward, or sown as a pure block. Its high palatability to sheep in summer makes it difficult to maintain strongly in a hard grazed sward, as the slightly raised crown becomes exposed and the growing point eaten out.
Pure stands can be used as a 'lamb finishing' summer feed to fatten lambs for sale at a time of year when pasture crude protein and metabolisible energy concentrations are often low. In the critical late spring and early summer period when lambs need to be 'finished' to slaughter weight before pasture growth slows down in summer, dedicated 'lamb finishing' inter-rows comprised of mixed chicory and white clover are significantly superior to swards of ryegrass and clover, or tall fescue and clover (around 50 chicory plants per square metre maximises production).
The best known cultivar is 'Grasslands Puna'. Recently, 'Choice', a selection of 'Puna', has been released. It is claimed to be a true perennial chicory, have 'improved' persistance, and to grow into cooler weather for longer before becoming dormant. This chicory has also been selected for lower levels of lactucin and lactucopicrin, sesquiterpene lactones responsible for the bitter taste of chicory. The reason for doing this was to reduce 'taint' in cows milk. However, these bitter compounds also protect the plant from grazing early in the season where other feed is abundant, thus helping it establish. Other cultivars include 'Chico', 'Forage Feast', 'Grouse' and 'Lacerta'.
It is possible to establish chicory in autumn if it is sown early enough to establish before becoming dormant, but it is most successfully sown in spring. Chicory usually establishes well in spring once soil temperatures are over 12oC, even if the growing season after establishment is dry, as the roots of young plants are able to quite quickly penetrate the soil to relatively deep levels (45 cms after 3 months). Sow the seed very shallow, at about 5 mm deep. It takes a bit less than 6 weeks to reach the four leaf stage, when it is counted as established.
Plantain (Buckhorn plantain,
A relatively drought and heat tolerant perennial palatable to sheep. The leaves are long and narrow, and held erect in improved selections. The root system is normally adventitious (branching, usually without a single distinct taproot), but plantain is still relatively drought tolerant. Plantain is widely adapted to soil types and pH levels, and grows well even in soils of relatively low fertility. Seed matures in ungrazed stands from early in mid-summer on. Irrigated pure plantain summer swards have given very good lamb liveweight gains of 222 grams per day. Plantain/legume mixed swards give as good grow rate for sheep as grass/legume swards. Grazing has to be managed to make sure vigorous clover and ryegrass growth don't shade out the plantain. Trials with irrigated plantain compared to irrigated high endophyte perennial ryegrass showed lambs grazing the plantain had double the selenium and copper liver levels than those grazing the pure high endophyte ryegrass. P. lanceolata has unidentified phytochemicals which are active against brown stomach worm, Ostertagia ostertagi. Whether concentrations consumed in normal grazing are useful to reduce worm burden isn't known. Rank and flowering plantain is less platable to sheep; young leaves have the highest feed value. Strategic nitrogen applications keep it vigorous and growing new leaves. Plantain will continue to grow in dry conditions, with yields similar to dryland grasses such as cocksfoot. Like most sward species, it must either be allowed to retain sufficient leaf area to fuel regrowth, or spelled long enough for regrowth from reserves (and left ungrazed long enough for subsequent reserve replenishment). Several cultivars have been developed, with improved tillering, greater productivity, and more upright growth.
Cultivars are `Ceres Tonic' and `Grasslands Lancelot'. 'Tonic' has large leaves, a higher crown, maintains its erect growth habit under hard grazing, and has better winter production; 'Lancelot' is bushier and tillers freely when closely grazed by sheep; but when very hard grazed it may become a prostrate rosette. Like chicory, plantain takes around 6 weeks to grow to the established four leaf stage. Plantain can be sown in autumn or spring, but spring sowings are generally much more successful. Sow relatively shallow - no more than about 1 cm. Plantain emerges quickly (about 3 weeks after sowing); the germinating seeds have long narrow seed leaves, and can easily be mistaken for grass. Seedling plantain doesn't compete well with strong growing ryegrass seedlings sown at the same time; it is better sown with slower establishing grass species such as tall fescue or cocksfoot. The seed is very long lived.
Sheeps burnet salad burnet, Poterium
A prostrate, pinnate leafed perennial that is relatively deep rooted (tap roots have been measured at greater than 60 cm) and highly palatable. While its deep rooting character allows it to withstand moisture deficit, its very high palatability to sheep makes it difficult to maintain in a hard grazed sward. It tolerates infertile soils, but grows best in less acid soils. It grows well in mild winters, growing best in spring, and persisting in summer even on poor and dry soils. Anecdotal evidence suggest it may help sheeps resilience to intestinal worms.
Yarrow Achillea millefolium
A spreading, finely dissected leafed perennial very palatable to sheep. Yarrow is extremely drought resistant, but can suppress some grasses and clovers unless it is grazed hard in spring. As long as it is not allowed to seed, it can be a useful adjunct to a permanent sward, especially in light well drained land subject to drying out.
White Clover Trifolium
A productive and persistant perennial clover species adapted to both high and low fertility soils, including moderately acid soils. White clover has white flowers, smooth trifoliate leaves and creeping stoloniferous stems which root at some nodes. There are both upright and more prostrate forms. Upright clovers are best suited to cattle, whereas prostrate clovers are less likely to be grazed out, and therefore the best clover to use for swards grazed low by sheep. Intermediate height forms suited to both sheep and cattle have recently been developed. A high proportion of white clover in the daily grass graze is strongly preferred by sheep in summer, and is high quality feed, but most cultivars are only moderately water deficit tolerant (but tolerate wet soils reasonably well). On sandy soils with slopes facing the sun, more drought tolerant cultivars should be used in the orchard inter-row. Other cultivars are liable to die out under these drier conditions.
A prostrate, densely stoloniferous, very persistant, small leafed
Tahora'. 'Grasslands Huia' is a widely adapted strong
weak autumn/winter clover, being more upright than 'Grasslands
Tahora' but still suitable
for sheep grazing as long as it is not grazed too close for too
is an intermediate height clover that persists under sheep
drought tolerant, clover root weevil tolerant, and with improved
growth. 'Triploi' is a New Zealand cultivar of North
with outstanding drought tolerance. 'Bounty' is a persistant,
cultivar with good autumn activity, 'Sustain' has good
and improved winter growth; 'Demand' has twice the number of
of most popular cultivars, making it very persistant under
grazing. 'Apex' has very good production
across seasons, is
relatively disease resistant, resists clover weevil, is
drought tolerant (and flowers and seeds early, important for
re-establishment in drought), spreads strongly, has many growing
on its stolons, thus making it very persistant under grazing.
'Grasslands Pitau' has improved winter activity
relative to 'Huia'. The
large leafed 'Kopu II'
one of the highest winter and total seasonal productions of
`Daeno' is one of the few clover cultivars that grows markedly
the cooler temperatures of late winter. 'Emerald' is a large
cultivar most suited to beef and dairy, but it also has a high
Seed germination of fresh seed of about 80% falls to around 60%
four years and decreases quickly in germinability and vigor after
although some germinability will be retained for many years. White
seed needs more warmth than ryegrass to commence growth, so is
in early autumn in order to establish before winter stops its
it can also be sown in spring once the soil warms. It should not
sown any deeper than 5mm, and must be sown into a firm bed, and
well after sowing. White clover should not be grazed too hard in
first year; grass should be 'held back' by avoiding nitrogen
applications in order to favor the maximum growth and spread of
White clover is self infertile, and requires pollenizing insects (mainly honeybees and bumblebees) to set seed. It ripens and drops seeds from early summer onward in spelled pastures. Some seeds have hard coats and will survive in the soil for some years, other seed is soft coated and germinates in favorable autumn conditions.
Red Clover Trifolium
A biennial or short lived perennial with dull foliage covered in fine hairs and somewhat conical pinky purple flowers, red clover is taller than white clover, and has a deep rooting system, allowing it to produce very strongly in dry summers where white clover becomes dormant and unproductive. However, it is not very active over winter. Like white clover, red clover tolerates poorly drained and clayey soils. Red clover is highly nutritious, with a greater proportion of rumen digestable protein than white clover. The older cultivars had relatively high levels of phytoestrogens (the isoflavone formononetin) which, in excess, can interfere in the ewes reproductive cycle. Newer cultivars, such as ‘Grasslands Pawera’ are lower in phytoestrogen, and thus safer for the breeding flock, have more disease resistance, and are more persistant. 'Sensation' is an early flowering newer cultivar with improved persistance, and has superior overall production, with very strong early season growth that continues on into summer. Red clover is often sown with white clover in the ratio of 2 of white clover to one of red. Red clover is not very persistant, the original plants often disappearing after four years, but its vigorous seedlings establish particularly well - in contrast with the much slower establishing white clover. As the seed is about three times larger than white clover, the amount sown needs to be higher.
Subterranean Clover Trifolium
This prostrate, large seeded annual clover has dull, broad leaves covered in fine hairs, and small florets. It is very persistant in free-draining quick drying swards; but its persistance is primarily due to self-seeding in summer, with the plant having a mechanism to bury its seeds in the soil surface ready for autumn germination. A portion of the mature seeds are 'hard' seeds that remain dormant for several summers. Its summer production is thus poor - or even zero. Its strength is as a winter clover that can survive severe summers as seed. In winter, it can out-produce both white and red clovers. It is often used with intensively managed kikuyu swards to help provide winter production when the kikuyu is dormant. For moist areas, a mix of white and subterranean clover will meet both summer and winter production. Sub clover should not be grazed heavily once flowering starts, or there won't be enough seed set for regeneration. Earliest varieties commence flowering in winter when every bite of pasture is needed. Hard seeds need to be at least 20% of the total seeds set if the clover is to persist longer term. Subterranean clover has very low levels of phytoestrogens, and thus does not affect sheep fertility.
Cultivars include 'Denmark', 'Goulboune', 'Grasslands AK 1003’, and 'Mt.Barker'. 'Daliak' is a mid season variety, and matures a high percentage (about 50%) of hard seeds in mid spring when there is less grazing pressure. 'Leura' is a very prostrate cultivar.
Sub clover is sown in autumn, and is compatible with most perennial grasses, including tall fescue and cocksfoot. Sowing rates need to be higher, as the seed is large. Ideally, around 150 subterranean clover seeds per square metre will give a good sub clover component when sown in a mix with white clover (at 280 seeds per square metre) and grass seeds. Light grazing can be started about 6 weeks from germination.
Caucasian Clover (Kura) Trifolium
A highly palatable long-lived perennial clover with a strong tap root and masses of underground rhizomes that allows it to both grow well in summer (when it produces leafy growth from short stems near the soil surface) and to persist in spite of drought. (But conversely, unlike both white and red clover, it is intolerant of temporary flooding). However, while persisting in drought, it tends to stop producing. It ceases producing new foliage before red clover. Kura recovers well from very hard grazing - an important attribute for a summer feed species. It is also productive in spring when stem production and extension occur. It has some ability to spread via its underground rhizomes into bare patches in a sward. Its ability to significantly surpass white clover in legume mass in spring and summer is a plus, but, unlike white clover, it is fully winter dormant. Although it is capable of producing very good amounts of feed due to its leafy nature, and is superior to white clover in very free draining droughty soils, the lack of winter production allied to its very slow establishment means it perhaps should form only a part of the legume component of the sward. It perhaps should be sown with white clover, given white clover is at least somewhat winter active (Caucasian clover gows well in association with red and white clover, and with birdsfoot trefoil). It might have an application as a specialised summer sward, in tandem with a summer and winter active grass such as tall fescue, perhaps on sunny slopes, where it seems to establish best.
Caucasian clover should be sown shallow, 6-12mm, and survival of the young plants is totally dependant on the correct rhizobial bacterial inoculant being present in the soil, or, for preference, only using inoculum coated seed. Sowing can be done spring or autumn, and typically would be done with a suitable slow establishing companion grass such as tall fescue, timothy, kentucky bluegrass, or phalaris. As caucacian clover is very slow to establish, the grass component has to be regularly cut or grazed to give the small clover plants every chance. Because ryegrass seedlings are so vigorous, it is best to oversow ryegrass (and festucaloliums) only after Caucasian clover has established. Weeds can be suppressed by grazing with hungry stock, being careful to promptly remove the sheep once the weeds have been knocked back. Control of weeds and of companion grass growth is essential for the first seasons growth if it is to have sufficient root mass to establish. As Caucasian clover is so uncompetitive as a seedling, it is very difficult to successfully oversow it into an existing sward. Cultivars include 'endura'.
Crimson Clover Trifolium
An erect growing annual clover with hairy leaves and elongated bright red flowers. Crimson clover is best adapted to reasonably well drained heavier soils, as it is relatively shallow rooted and is intolerant of excessive dry. Its strength is in its cool season growth, producing better than most species in winter. It also produces well in spring. Flowering commences in spring, and should not be grazed too heavily in late spring and early summer if seed is to set. Like other annual clovers, it regenerates from seeds matured in summer, and which germinate in autumn. Sow in early autumn. For best production, it ideally should not be grazed until it has made 15 cm of growth.
Balansa clover Trifolium
An autumn, winter and spring active semi-erect annual clover with whitey-pink flowers. This clover can grow nearly a metre high when ungrazed, but tolerates grazing well, when it forms a prostrate plant. Balansa clover is widely adapted to different soil types and can stand some waterlogging. Balansa clover is highly productive, especially in spring, and once well established, needs to be grazed regularly to maximise production up until its flowering time, when it should be left ungrazed to form seeds. Reseeding occurs as the seed falls to the ground over spring and early summer. Much of the seed has a hard coat, which softens over summer, finally germinating in autumn. (Some of the hard seeds remain dormant in the soil for several years.) So long as the summer sward has been grazed down far enough to encourage the new seedlings in autumn, there will be good natural regeneration. Balansa clover will persist in the sward for some years by annual self seeding alone - if it is well managed. Balansa clover is usually sown in autumn, with full productive maturity being reached 3 to 4 months later. It establishes particularly well with slow-to-establish grasses such as cocksfoot, when it can make up as much as half the balansa/cocksfoot sward by spring. There are only low levels of phytoestrogenic compounds involved in reproductive disruption. 'Frontier' is an early maturing cultivar, 'Paradana' mid season, and 'Bolta' is a late season cultivar.
Lucerne Medicago sativa
A very deeply rooted (2 metres or more) legume that is capable of producing feed in the driest summer - if pests and diseases are kept away. Newer more pest and disease resistant cultivars such as 'Otaio' are available, and may prove more persistant. It does not compete well with grasses, so has to be sown as a pure stand, or in alternate rows with grass. Alfalfa requires high fertility and good management if it is to succeed. Lucerne can increase the risk of bloating at certain times of year. Newer varieties include 'Dekalb', 'Mycogen', 'Land-O’-Lakes', and 'Pioneer'. The best new varieties have increased disease resistance and markedly improved grazing tolerance (recovery).
Birdsfoot trefoil (Lotus
A deep rooted (to 2 metres) perennial summer legume with small heads of bright yellow flowers (usually 5 flowers per umbel) of variable strains and regional types, providing dense, non-spreading patches of nutritious foliage, but tending to become dormant in extended dry periods. Better adapted to less fertile areas than lucerne (although slightly less drought tolerant), but does not compete well with vigorous grasses and clovers in higher fertility soils. Its rhizobia are different to L. pedunculatus, and it does not establish where they are not present. Birdsfoot trefoil tolerate more acid, low fertility soils better than white clover. It is tolerant of wet soils. It will not stand continuous hard grazing, and does not have the insect resistance of L. pedunculatus. Birdsfoot trefoil is naturally a teraploid plant. Cultivars include 'Empire', 'Mansfield', and 'Viking'.
Burr medic Medicago
A low, prostrate to semi-erect annual with lotus-like glabrous leaves and tiny yellow flowers. The seeds are in the form of a small burr, many of which are drought resistant 'hard' seeds, and thus reseed well. It requires a medic-specific rhizobium inoculum (type 'N' Rhizobium). Burr medic is not as deep rooted as some clovers, and fixes less nitrogen as a result. Cultivars include ‘Armadillo’. It can be sown in spring or autumn, and if the soil is moist, a summer sowing can give feed into late autumn and early winter. As it is both relatively shallow rooted and winter dormant, it may have a place in the citrus inter-row sward.
The conventional system is to spray out the existing sward with a broad spectrum herbicide, rotary hoe to a fine tilth, either hand broadcast or tractor drill the seed of the improved sward species, and finally tractor harrow or hand roll to firm the seedbed and lightly cover the seed.
Direct drilling without rotary hoeing
If the trees are spaced widely enough, the inter-row sward can be reduced to a very low height by intensive grazing or mowing, very carefully sprayed out with glyphosate (once it has recovered a little from mowing or grazing), and several weeks after the sward has died, a contractor with a seed drill on the tractor can be hired to direct drill seed of new pasture species of choice.
Using large machinery is probably neither warranted or possible between the rows of even the largest home fruit orchard. Walk behind rotary hoes are certainly possible, although they may struggle if there is a lot of dead herbage to contend with, and they will definitely struggle to deal with dead kikuyu. In addition, there is the damage to tree roots.
Mow, spray, and 'scratch sow'
It is sometimes possible to very heavily mow or graze pasture in early autumn and surface broadcast white clover seed in expectation that autumn rain will enable it to germinate even altho it is not buried. If it rains soon after broadcasting (washing the fungicide and insecticide coated seed off the foliage), sheep can be returned for several days to help tread it in. This idea is somewhat successful so long as there is no extended dry period. Obviously, it can only be used for a portion of the pasture at a time, or, if strike is poor, winter feed reserves may be comprimised. It is also time consuming and laborious, and results are very variable.
A similar small scale row by row approach can be used to establish preferred grass varieties, except that the existing sward will have to be mowed, the clippings removed, then sprayed out once regrowth starts. Several weeks after spraying, and in conditions of fully moist soil and impending rain, the dead weed and grass stubble has to be removed as best as possible with a three pronged hand cultivator, a rake or a hoe.The grass seed has to be broadcast and crudely scratched in with a rake, then firmed by foot. On heavy soils, it may be better to lightly sprinkle sand over the seed (or mix the seed with the sand ) rather than try to scratch the firm surface. This is a tedious, difficult, and not particularly reliable method, but the establishment of patches of better performing grasses may make it worthwhile in small scale home orchard conditions. This approach is really only suited to grasses such as ryegrass with vigorous seedlings and which are relatively fast to establish in autumn. Trampling by sheep contained in the grazed out sward is also useful for helping the grass seed make contact with the moist soil surface.
The same technique of grazing (preferably) or mowing, followed by spraying when regrowth starts, and then broadcast into the raked thatch can be used for sowing herbs such as chicory, except the operation is usually done in spring.
Every time the sheep are shifted to another part of the orchard the eaten - out sward can have bare patches sown to better species, small areas can be skimmed clean with a sharp hoe and resown, or potted plants of long-lived spreading legumes like caucasian clover planted out. Obviously, this can only be done in autumn (and to a limited extent spring). So long as it is possible to temporarily fence off the young sward for a couple of months, the renewed patches should survive.
However the sward is renewed, most newly sown grasses and clovers should be left ungrazed for about six to eight weeks. It is important to either mow or lightly graze it after this time to encourage the grasses to thicken up by forming new basal sprouts (tillers), and to allow light to the new clover (if it was sown with the grass). But the new sward must have enough root growth to securely anchor it against being pulled out by grazing sheep. This can be roughly checked by the 'pull test'. Hold a young plant about half way up its height and pull on the leaf blades . The leaf blades should tear off rather than the plant pull out of the ground. Seedlings in a finely rotovated tilth from a fully sprayed out seed bed take longer to anchor firmly than plants oversown into a minimally disturbed existing mown or grazed down sward.
Clover and other legumes sown into a heavily grazed sward will get the best start if the grass regowth is grazed heavily one more time, when the young clover has just established (but not so heavily the sheep start on the small clover plants). Ideally, the sward would then be left for the clover to grow on for six or so weeks.
Unseasonal dry spells in autumn can put young grass seedlings at risk. Their roots are still mainly at the surface, preventing access to moisture deep down. But this disadvantage can be turned to your favor. Timely light showers and heavy dew will help young grass survive as its surface roots can respond quickly to moisture, and it doesn't have a large leaf surface area to support. But it needs water regularly if it is to survive until good rain. If there is a gap in showers, or little dew, even a relatively small amount applied from hose and domestic sprinklers, applied in the evening when it won't just evaporate, may 'step' the young plants through and make the difference between wasted effort and an invigorated, more productive autumn sward of better pasture varieties.
Unless the sward is on a very fertile soil, a light dressing with
helps the young grass re-grow quickly after its first light
or three weeks later, with the nitrogen in place, the root system
be well established, nitrogen should be available, and the sward
be near its full growth potential.
Grazing sheep in an orchard - JJ brief notes on selecting sheep that are easy care ("low input") in an orchard situation
The information in this site is largely the personal opinion of the author, although it is written in good faith. It is up to the reader to criticize, read alternative opinions and assertions, and come to an independant view. Do not rely on anything in this site being current, correct or factual.
The author rejects any responsibility for any decisions about life, sheep management, fertiliser rates or practices, or anything else other than his own. Any action you take after reading the material here is soley your responsibility - seek advice from others, read critically and widely, don't accept everything you read here. You have been warned! Question everything.
Use the information
as a starting point for questions. Don't believe what is
Form your own opinion on these matters after reading widely
appropriate professional advice.