'Cal Col'. Deniliquin. NSW 2710
High productivity and good quality are most important attributes to strive for in pastures, but a past emphasis on these factors alone has not served us well. The other attribute that we must also address is that of pasture stability. How long does a pasture last before it runs down, either in terms of composition or productivity? What types of pastures might give a more even production across the seasons with less boom and bust? And how might we manage pastures to maintain the species we want, without the need to resort to cultivation and resowing? These are some of the issues that I want to raise at this Conference.
The associated factor of pasture management is something that we have also largely ignored. Continuous grazing has been regarded as the norm and if a pasture cannot stand hard continuous grazing, then that is the pasture's fault and it should be sent back to the research station to be rejigged. But such an attitude is responsible for a lot of pasture rundown and many a dollar lost because otherwise valuable species have not been planted. Lucerne is a simple example of a plant that can fatten plenty of lambs, but has a reputation for being hard to manage and for having a short life. Yet in the right hands it can be planted across whole farms and remain productive for 10-15 years.
I have boldly called this the biological control of the future. Biological, because it arises from the
manipulation of defoliation, seed set and plant survival by grazing and resting at appropriate times. The future, because I believe we will see pasture management increase considerably over the next 10 years, both as a science and as an art of the farmer. The end result will be pastures that will last a lot longer, with the desirable species dominant, than they do at present. Farmers do not resow often (areas resown are as little as 2% of pastures annually). Why spend $200/hectare resowing a pasture, and a whole year out of production, if it soon degrades again to a bent grass or vulpia sward?
In this paper I present some thoughts on both pasture stability and management. This is drawn partly from my scientific background, which is mainly in the rangelands, supported with my recent experience of pasture management on my small farm at Deniliquin.
The main purpose here is to present some of the principles of stability, which I think are often ignored. However, I need to first address the matter of what 'stability' is and why it is important.
Under this heading of stability I include three attributes - stability, resilience and sustainability which I have lumped together under the heading 'stability' for convenience.
Stability refers to the degree of variation, both between seasons and between years, the latter arising mainly from variation in rainfall. A pasture with a high variation is less useful than one with a low variation, because of the feasts (usually in spring) and famines (usually in autumn or winter). As an example, on my farm the species with the most variation in value throughout a year would be the annuals, wild oats, barley grass and annual ryegrass. They have excellent growth and quality in late winter, but no growth or quality in summer. In contrast, the native whitetop (Danthonia caespitosa) never grows fast, but has a long growing season and will respond to rainfall at any time of the year.
Resilience refers to an ability to withstand shocks, without being changed. The usual shocks to a pasture are drought, flood and heavy grazing. Fire might also be a factor. Whitetop is also high on the resilience scale, being tolerant of most situations in my area. However, resilience is not an attribute to be pursued by itself: bent grass could also be described as very resilient, but of no value because of low productivity and quality.
Sustainability refers to long-term trends in composition and productivity. Downward trends might appear because of changes in soil pH or fertility, or because of the cumulative impacts of grazing.
Whilst the ecologist might distinguish between these three attributes, it is a workable generalisation to combine them under the one heading of stability.
The importance of 'stability' can be simply illustrated by a glance at a seasonal feed budget, where growth exceeds demand at one time of the year and is below demand at another time. Forage grown (or stored standing) may be worth
$100 per tonne (the cost of purchased fodder) in the trough period, but only $10 per tonne during the peak of the growing season. The value of stability can also be illustrated by a look at pasture renovation budgets. Pasture resowing can be expensive, particularly if a nuisance mat-
forming grass has to be eliminated in the process and the paddock is out of production for
a year or more. The budget looks a bit sick if the real pasture life is only 5-7 years, compared to the expected 15-20 years.
High pasture productivity is not enough. Pastures have to last, and management can be one of the ways to ensure that they do.
PRINCIPLES OF STABILITY
It will always be difficult to specify in any detail the types of pastures that are stable, mainly because every mix of soil type, rainfall, season of rainfall, crop/grazing rotation and farm forage demand will have a different best pasture type. Under these circumstances, it is more useful to outline some of the principles that we might look for in a stable pasture. Some of these are as follows.
1. Dominance of perennial species
It is now quite clear that perennial pastures have a lower seasonal variation in production, are more resistant to weed invasion and have less soil acidification than annual pastures. This does not necessarily mean that they will be more productive in terms of animal weight gain. Annual species may produce more forage than perennials when rainfall is ample, and this may be of higher quality. However, annuals fail when rainfall is low or out of season. Annual pastures fail to use moisture that comes over the summer (e.g. in summer when some farmers think it shouldn't), so that burrs and other weeds take up the slack, and soils deteriorate from lack of cover.
The assumption often is that perennials are only for higher rainfall areas. The work of Kemp and Dowling (1991) showed that pastures with rainfall above 800-900 mm are the only ones dominated by perennials, whilst pastures with
rainfall below that level are dominated by annuals. I accept that lower rainfall pastures will always have a proportion of annuals, but there is no need for annuals to dominate. At 400 mm rainfall, I have paddocks dominated by the native perennials whitetop and curly windmill grass, whilst others are dominated by lucerne. It is simply necessary to choose or find perennials to suit the soil and climate.
There is also an assumption that perennials are incompatible with crop/pasture rotations. However, I believe that this is simply a matter of our current mind set. Perennials can be sown in the longer rotations and some native perennials can be retained in 1-2 year crop cycles that do not destroy the seed bank in the soil. Some work is proceeding in the Victorian Department of Agriculture at Bendigo on sowing cereals directly into existing lucerne stands that are retained under the winter cereal crop. Research is still incomplete, but it would seem that it can be successful if the lucerne is a winter dormant lucerne variety, the crop is vigorous and if there is some chemical suppression of the lucerne. I believe that it should also be possible to sow cereals into native perennial pastures where there is some weakening of the pasture by non-lethal doses of chemicals (e.g. Roundup) and control of root diseases, but that is something for the distant future. Perennials can and will be used in crop/pasture rotations in the future as our knowledge of how to do it is developed.
2. Native perennials
We have mostly ignored the local perennial native grasses that we have, or once had, on our farms. Yes, they are of lower productivity than the introduced species, and they are of lower quality. But they are more stable. They are adapted to the soils and climate, and so withstand the droughts and floods. Last year I had an encroachment of the flood water onto 'Cal Col' for several weeks during the spring. The result was a dead lucerne stand, and some rather sorry subterranean clover and ryegrass, both of which failed to give any forage from the subsequent summer rains and provided no check to the excellent strike of Bathurst burr. In contrast, the perimeter of the paddock, which
still retained the original whitetop pastures, recovered to provide an excellent green sward through until April. I have also mentioned earlier their ability to respond to rainfall whenever it occurs and I am still utilising the forage that grew after the March rains. This is not to argue that natives will always be best, but rather that they have a place, particularly where fertility is low, soils shallow or stress of drought or flood is high. They have the advantage of low cost and stability, which can more than make up for their lower quality and productivity.
Pasture legumes are important for both soil fertility and forage quality. They must be a part of any pasture. A reasonable target would be 25%. This is generally understood and no further case need be presented.
4. A variety of species
We commonly think of the Riverina as being winter rainfall, but on average 40% of the rainfall comes in the summer 6 months. The average also masks a great deal of variation. Sometimes the rainfall is mainly in winter, other times it may fall in summer and occasionally it may fall in both winter and summer. This variation is only a problem if we are not prepared for it. A mixed pasture or, alternatively, different species in different paddocks, where some species can respond to rainfall whenever it occurs, means that rain is always used to advantage. If we rely solely on winter annuals, we will be missing out on an important part of potential pasture production and facing a risk of soil degradation and weed invasion. Alternatively, if we rely solely on perennials, we will be foregoing an important source of forage quality and winter production (which can come from the gaps between the perennial tussocks).
My experience of species response on 'Cal Col' is shown in Table 1. Annuals are the most useful species in winter, lucerne the most important species in summer and the native whitetop the most important species during autumn. The autumn advantage comes mainly from stored half-green grass, rather than from growth, but this is quite satisfactory at a time when the sheep demand is for maintenance rather than growth. Annuals and lucerne are the most variable (but these can be grown together), whilst the perennial grasses are the most even producers. Phalaris is not recommended for rainfalls below 450 mm and may die out in a drought, so it remains experimental. The native whitetop, which is dominant where the plough has been kept out for 10 years, is clearly the most stable, despite the lower productivity. This is not to say that it is the choice of species for the whole farm. The higher quality of lucerne and annual subterranean clover and ryegrass are important for putting weight on animals and should be grown on at least part of the farm. This may not be true when the enterprise is wholly wethers for wool, when pasture quantity is the main target and it is unlikely to be rewarding to pay extra for pasture quality. These pastures (annuals and lucerne) also fit more easily into a crop rotation on the better soils.
Table 1. The species by season matrix of value for common dryland pastures at Deniliquin (400 mm rainfall, 60% cool season).
Annual ryegrass Barley Lucerne Danthonia
and subterranean grass
Winter: wet + ++ +
dry + +
Spring: +++ + +++ ++
Summer: wet +++ ++
dry + + +
Autumn: moist ++ ++ ++
It is apparent to me that stability is a most important attribute of a pasture, yet it is one that is never mentioned in research results. Indeed I do not think that we even know how to measure it. Furthermore, it is probably not correlated with animal productivity in any single year. There are several recent research results from the rangelands which suggest that annual pastures will yield better cattle and sheep
production than perennial pastures in average and above average years, but the reverse applies
in the dry years. Annual species have a higher digestibility and protein content during the growing season, but do not persist over the dry season (Ash and McIvor, 1995).
5. Not continuous grazing
Continuous grazing, which is the norm on most farms, is probably responsible for much of the gradual decline that we get in many of our pastures. Continuous grazing places a heavy burden on the more palatable species, particularly those components which stay green longer than others or grow out of season. These are the very species we wish to retain because of their contribution to extending the period of weight gain and because of their ability to reduce land degradation. Once again this may not correlate with highest animal production, which usually comes from continuous grazing, at least in the short-term whilst the pasture lasts. Systems of grazing management must be viewed in terms of their ability to encourage the target pasture composition, not in terms of any ability to deliver short-term gains in animal productivity.
I have argued that farms should be using some type of grazing regime other than continuous grazing. But what regime? Once again you will not get a prescription. This is partly because I do not have one, and partly because I believe that the prescription will be different for every pasture type and every farm. Management is a matter of encouraging one species and discouraging another, so the best regime will depend principally on the characteristics of those species. It will also depend on the soil and the climate. The one species may be easy to retain in one situation where it is really at home, but difficult to retain in another where it finds the habitat more marginal. Hence the grazing system needed for Goulburn may be different to that needed for Wagga or Deniliquin, even if the species is the same. Finally, the demands and opportunities for management will vary with the farm. Each farm will have different mixes of soil types, hills and flats and sheep or cattle, and hence the optimum system will be unique to it, not a clone from another farm, region or country.
So once again I resort to presenting a few principles.
(i) Manage towards a species target
Every grazing management system needs a specific species target. What species is wanted? What species are not wanted? We can mostly ignore the large body of species in between that do not matter that much. Quality species will be important for breeding enterprises, whilst high carrying capacity species will be required for wether enterprises. As an example, phalaris might be the preferred species for wethers, whilst lucerne might be the preferred species for growth in young stock. As with other objectives, you will not make progress if you do not know where you wish to go.
(ii) Manage competition
Competition between species achieves most of the end result in grazing management. Annual ryegrass reduces Vulpia, perennial grasses reduce weeds such as Paterson's curse, lucerne squeezes out heliotrope, to name just a few. So grazing management is targeted at favouring the desirable species and disfavouring the undesirable species. This is the opposite of continuous grazing, which disfavours the desirable species.
(iii) Manage seed set
Annual species depend on seed banks to establish their place in the pasture. So the species that sets the most seed in spring will start next year with an advantage. Hence we can encourage subterranean clover by avoiding tall pastures and improving phosphorus nutrition. We can encourage annual ryegrass by undergrazing in spring when stock eat the seed heads. We can discourage Vulpia by heavy grazing early in the spring when the seed heads
are forming and by resting later in the spring when the ryegrass is flowering.
(iv) Manage survival
Some species need rests at certain times of the year if they are to survive. Lucerne needs some rests between hard grazing. The newer phalaris cultivars need some leniency during spring. I recently visited a farm near Kilmore, Victoria. I was surprised to see a dense sward of phalaris in the stack paddock and along the plantations, which was in stark contrast to the surrounding paddock of sweet vernal and bent grass. The paddock was continuously grazed by sheep. The contrast suggests that there is a great management opportunity being missed on that farm, simply through the encouragement-discouragement principle, affecting the relative survival of the two dominant species.
(v) Manage establishment
Most species are more sensitive to defoliation when they are young. I attribute the re-establishment of the native whitetop and curly windmill grass in my pastures to resting during the wetter springs, when establishment occurs. Within this principle there is no requirement for regular resting or even resting every year. Resting at a critical time, only perhaps once every 5 years, at a time when resting is easy because of the abundance of forage, is all that is required.
(vi) Manage total grazing pressure
If total grazing pressure (usually termed stocking rate) is too high there will be no resting options. Conversely, if grazing pressure is too low there will be no hard grazing options. The best grazing pressure will probably be a variable one, given that the rainfall in Australia is variable. On 'Cal Col' I achieve this not by buying and selling, but by lambing in July-August and selling those lambs in February-March, so that grazing pressure is least during the low production period in autumn-early winter. For some graziers in the west, managing grazing pressure can most easily be achieved by limiting the offtake of pasture by feral animals and kangaroos.
(vii) Manage with the aid of technology
An emphasis on management to control pasture composition does not exclude the sensible use of low cost technology. Fertiliser is needed for legumes, fodder conservation might clean up the seed of an undesired species (needs attention to timing - cut early) and spraytopping might shift the species balance in your favour (e.g. many native perennials are tolerant of Spray.Seed). Roller wipers can be used to great advantage to remove taller weeds, such as speargrass and rushes. The native speargrass (Stipa spp.) appears on the lighter soils of the western Riverina after some years of no cultivation and may require spraytopping or roller wiping to keep it in check.
(viii) Be farm specific
As I mentioned above, the optimum management system will be farm specific, because of the unique characteristics of each farm. Sometimes a subtle change in soil texture or moisture (runon or runoff) is sufficient to shift the species dominance and each farm's livestock types and forage needs will differ. It may be possible to separately fence the soil types, but in other cases this will not be feasible and management must adopt to this situation. This will mean that each farmer has to devise his or her own management system. Research can be critical in devising methods that can be trialled, but this cannot replace the keen observation by the person who is on the spot.
Options will arise according to the mix of hills/flats and heavy/light soils on a farm and these are options that cannot be considered on a research station. On 'Cal Col' I have three soil types, each one being best suited to different species combinations, and each having a different season of major use. These are presented in Table 2. The clay-loam soils with Danthonia provide the grazing emphasis in autumn-winter (much of it on standing-stored forage), the heavy clay soils with annual ryegrass and phalaris provide the grazing emphasis in spring and the sandy clay soils with lucerne provide the grazing emphasis in summer.
Table 2. The principal pasture types on 'Cal Col' and their emphasis of use
SOIL BEST SPECIES PROBLEMS MAIN FEATURES
Red clay- Native Stipa Autumn- Low cost,
loam (spear winter long growing
Heavy Annual Spring High
grey ryegrass nutritional
clay Native value
Light Lucerne Flooding, Summer High nutritional
sandy (+subterr- Bathurst burr value
*Experimental - not recommended at this rainfall
I also have the unique option of a zero cost supply of mulch in the form of waste rice hulls from the local rice mill. Rice hulls are a rather harsh type of organic matter, but I have found that they provide an excellent barrier to evaporation. I have them spread over the perennial pastures at about 40 tonnes/ha (4 cm deep). All current forage is covered over and lost, but there is a growth advantage of 30-40% on native whitetop and phalaris in the following year. It also encourages the germination of weeds, such as rushes, horehound and Bathurst burr, so it is not all gain. I am hoping that there will also be a long-term improvement in soil organic matter.
(ix) Monitor the outcome
A useful aid to observation is to record the pasture composition, annually, paddock by paddock, at about the same phenological stage (e.g. peak of flowering of annuals). A scientist might cut and weigh, whilst a farmer will be satisfied with a visual estimate. This has a few pitfalls: paddocks are not even, many differences arise simply from the amount of rainfall received that year and estimates can have a fair degree of bias towards the tall species with larger seed heads. Also, composition changes over the spring, with an apparent early dominance of short season annuals and a late dominance of perennials. Furthermore, you have to know the species! It also takes some discipline to remember to record each year. Its value is very long-term, because it takes about 5 years of records before they become useful.
This has been a rather personal view of two issues in pastures that I have given much thought to in recent years. The first of these is the need to consider stability as an important pasture attribute, which can be as valuable as productivity. Stability requires a shift to perennials, right across our pasture lands, including the croplands. The second is to use the
options that we have for managing our pasture composition, by using low cost means, such as when they are grazed and when they are rested. Grazing management, when combined with the low cost technologies that we can use to control the input of seed to the soil, is the biological control of the future.
The latter interest has come as a practitioner, and is contrary to my previous conclusion whilst engaged in pasture research, where I was interested mainly in the short-term results that can be measured by weighing sheep. The gains from better pasture management will not be realised in short-term weight gains, but from longer pasture life and reduced costs. In working towards this objective, the individual farm can take advantage of variation in landscape and paddock history, whilst researchers find such variation confounding.
This does not mean that I am enamoured with the current promotion of cell-grazing. Cell-grazing does not meet my criteria of managing to the needs of the species present on each farm and allowing for the options available on that farm. It is a system that is imported and applied
without thought and ought to fail in more places than it succeeds. But I do believe that continuous grazing is one of the causes of many of our pasture ills. On many farms it seems to be the only option because every paddock is apparently occupied in separating classes and ages of stock. But is the separation of classes and ages as important as it seems?
Native perennials may be one of the ways of restoring stability to some of our pastures. These species will be particularly useful for the soils of lower fertility and lower moisture holding capacity, where the returns from cultivation and sowing will be low. The value of native species arises from both their stability and from their low cost. Management to retain them, rather than sowing (domestication is now proceeding for both Danthonia and Microlaena) may therefore be the main method of farming these species. Retention begins with low tillage, because ploughing is the main enemy of native perennials.
1. Kemp, D.R. and Dowling, P.M. (1991). Species distribution within improved pastures over central NSW in relation to rainfall and altitude. Aust.J.Agric.Res. 42:647-59.
2. Ash, A.J. and McIvor, J.G. (1995). Land condition in the tropical tallgrass pasture lands: 2. Effects on herbage quality and nutrient uptake. Rangeland J.. 17: "in press".