The composition and quality of pastures is often less than desirable for sustainable, productive agriculture (Wilson and Simpson, 1993). We often accept pastures as they are, but know that they could certainly be better. There are many reasons for this lower quality, from declining fertility and acid soils to imperfect species and cultivars, and inappropriate management. We usually know if something extreme has been done that affects a pasture, but more subtle influences are poorly understood. There are many aspects to management of a pasture. One aspect that has been among the least understood is grazing management (Kemp and Michalk, 1993).

Grazing Management: what is it?

Grazing management is a general term that is interpreted differently by different people (Hutchinson, 1993). To those who are only interested in animals it often simply means the feed supply for livestock and how much comes from grazing. The rules they use to decide when and where to move animals and the claimed benefits from different systems are based largely on the condition of the stock. The major problem with this approach is that pastures can often deteriorate to non-sustainable conditions before animals do, such that damage is done before a decision is made to move animals. The time for a pasture to recover, if at all, is then considerably greater than may have been necessary. This animo-centric strategy can work if it is cheap to resow pastures and you can afford the time delay before pastures become productive again.

The animo-centric approach is also evident in those who have taken some consideration of how plants and pastures grow and develop. They have often concluded that some sort of a rotational grazing system should improve both pasture and animal performance. However, they then impose a rigid rotational grazing scheme on the pastures and animals that is maintained throughout the year and through good and bad years. Such schemes have rarely shown any advantages over continuous grazing, set stocking strategies (Hutchinson, 1993), except for specific species such as lucerne. This approach was the subject of a lot of research from around 1940 to 1970.

In retrospect, rigid schemes cannot be expected to work consistently as both animal demands and pasture growth rates are not constant throughout the year. Unfortunately, the main emphasis in this research was on animal measurements and little emphasis was placed on changes in pasture composition that may have been beneficial. The normal funding cycle of three years also meant that any changes which may have had a longer term effect could rarely be followed.

What has developed over recent years is an attitude that grazing management needs to consider the pasture as much as the animal in deciding what practices to follow and that a more flexible approach is needed. Grazing management now means more about managing

the grazing process (Hutchinson, 1992, 1993; Kemp, 1993). Continuous grazing of a pasture at a constant stocking rate is in effect zero management. The way animals graze a pasture is influenced by the state of development of the plants, the time they are on the pasture, the time the pasture is rested between grazing and the ability of the animals to choose. Stocking rates have the major influence on choice.

An important part of the current interest in grazing management is the realisation that the same tactics do not need to apply to all paddocks on a property at the same time. Most properties have a diversity of pastures and some diversity in stock. These can be used in combination to optimise management across a property. Only some paddocks may need special management in any one year.

In this paper, I will expand on the biology of grazing management and include some examples of the effects we have found from testing different grazing tactics on the composition of a range of pastures. I hope this will give you some ideas you may find useful in managing your own pastures. We consider that maintenance of a desirable pasture composition is the key to maintaining quality, sustainable and productive pastures. My comments will be largely confined to perennial pastures where the aim is to maintain them over the long term and assume that soil fertility is adequate for good pasture growth. Unless plants are able to grow then grazing practices cannot positively influence the pasture. I will, though, also make a few comments on annual pastures.

Grazing Management: a biological approach?

The biology of grazing is still one of the least understood aspects of livestock production. Good stockmen and the animal nutritionists have done excellent work in understanding what animals require for good production and pasture agronomists and farmers know reasonably well how to sow and make a pasture productive.

However, the interface between pastures and animals is still something of a black hole. We do know, though, the main components that grazing management can influence. Grazing management does need to take a biological approach. Both plant and animal requirements need consideration and the timing of events is important, the main aims being to manage the composition of a pasture to desirable ends while enhancing the performance of animals. A pasture is an ecosystem and needs to be managed as such. Pasture ecosystems also keep changing. Pastures today are different from those in the 1950s and management needs to adapt.

Grazing Management: why do it?

Why should you change from continuous grazing, or zero management, to something that may be more complex? There have to be some benefits. These benefits can be in terms of the pasture and/or the animals. The main gains may not be from greater animal production (Kemp and Michalk, 1993). Increasing the productive life of a pasture can pay dividends as weed control and resowing costs are reduced and desirable levels of animal production can be sustained for longer. Degraded pastures can be rejuvenated by appropriate grazing management, producing livestock products in the process. Once you know more about how to manage your pastures better you will be able to increase livestock production, but that should not be the first goal.

Pasture Plants: what are their needs?

The management of plants in a pasture requires consideration of their needs. Pastures are ecosystems that mostly have a mixture of desirable and less desirable species. Grazing management needs to encourage desirable species and suppress the less desirable (Wilson and Hodgkinson, 1990). Within a pasture most species have stages in their life cycles when they are most sensitive to competition from other plants and/or grazing. Grazing practices can be

used to target these stages and shift composition in a desirable direction. Grazing management requires a reasonable proportion of desirable species in a pasture in order to exert any useful economic effects.

The periods when most plants are sensitive to grazing are when establishing from seed and during flowering (Lodge, 1987). Perennial plants also need to build up reserves and to establish buds. Competition from other plants during the establishment phase can also reduce the incidence of a species. Other factors such as toxic litter can be important in this phase (Leigh and Halsall, 1994). When plants are flowering the production of new leaves, tillers and buds is often suppressed. Grazing the main growing points and leaves often results in plants being more vulnerable as they have to depend upon stored reserves for survival until any remaining buds are able to start growing (Kemp and Culvenor, 1994). Putting extra grazing pressure on undesirable plants during flowering is part of the strategy for controlling wire grass (Aristida ramosa) in northern NSW (Lodge and Whalley, 1985).

Plants need to grow and produce leaves so that they can photosynthesise and produce reserves that will be used for survival and further growth. Preventing plants from doing this by continuous, very heavy grazing would obviously result in the plant's death. This can be used for the control of weed species. However, the same rules apply to desirable species and grazing needs to allow for some growth, reserve replenishment and regeneration.

Pasture Growth Cycles: to rotate or not?

The greater the green leaf area per unit ground area the greater the growth rate of the pasture, until the pasture completely shades the ground and mature and dying tissues accumulate. This realisation leads to the argument that rotational grazing to maintain pastures in the (so-called) linear phase of growth (assuming a sigmoid or 'S' shaped curve) would be ideal. Pasture growth rates should then be maximised and plant survival enhanced. However, this theory has had some problems in application except for single species swards such as lucerne.

The growth rate of a pasture is not constant during the year and it is difficult to devise a system to maintain all pasture species in the ideal phase at all times. Maintaining a pasture at a level that maximises growth rates may also mean that lower growing species, such as some legumes, are shaded out and that plants become more erect and do not tiller as much. A further point is that at moderate stocking rates plants in a pasture are effectively rotationally grazed. Little is known in Australia of the frequency of grazing, but earlier work in the UK suggested that some weeks often elapse before animals return to graze a plant (Hodgson, 1966). The frequency with which plants are grazed increases as the amount of forage available per animal decreases.

The main instance where the use of rotational grazing has been exploited to increase pasture production has been in the New Zealand block (sometimes called ration or controlled) grazing systems (Clark, 1993), which has been adapted to Australian conditions (Beattie, 1993; J. Young, 1993; R. Young, 1993). In this case rotational grazing is restricted to the autumn-winter period when pasture growth is at a minimum and animal requirements are also low. The aim is to maximise the number of animals that can be carried through to spring. Pasture budgeting is used to ration the forage available to stock that are moved frequently, sometimes twice a day. Parts of a paddock may only be grazed once during the autumn-winter period so that the maximum amount of forage is available around lambing and calving times when feed demand is high. Just prior to lambing or calving, stock are put onto continuous grazing or a slow rotation until the following autumn (Sheath, Hay and Giles, 1987).

Pastures: adapted and developing?

The need for better management for pasture plants also depends upon the environment. Most pasture species will grow over a wide region. In the centre of that region they will probably persist no matter what management is imposed.

As you move closer to the edges of their area of adaptation, management becomes more important. Phalaris, for instance, will require more careful management at Wagga Wagga than at Orange. These effects also apply to the weed species. Weeds will be much harder to control in areas where they are well adapted.

The producer needs to consider the composition of the pasture suitable for animal production and appropriate to the phase of pasture development. These considerations provide the target composition for which managers need to aim. The nutritive value of pasture species is reasonably well understood; most producers have a reasonable idea of the species they would prefer in their pasture. However, to decide on the appropriate proportions of these species, the stage of pasture development needs to be considered.

Pasture composition does vary as a pasture develops. For example, pastures sown on infertile soils are often legume dominant in the first few years, assuming that phosphate and minor element deficiencies have been corrected. Over time such pastures become more grass dominant and as soil nitrogen increases nitrophilous weeds often invade. The pasture can be in (relatively) stable states during its development, with often rapid transitions between states (Westoby, Walker and Noy-Meir, 1989). Hutchinson (1992) found that a productive phalaris, white clover pasture at Armidale went through at least three states over a thirty year period, each state being different.

Our knowledge of pasture ecosystems is still limited, such that we cannot always provide appropriate guidelines for the better composition of a pasture suitable for different conditions. Current research aims to provide some guidance. This work is also based on the view that it is better to manage a pasture over a range in composition and biomass than to aim for a fixed point. These ideas have led to the development of the concept of a 'Pasture Management Envelope' (Kemp, 1993). To help in this work, benchmarks are being developed (Bell and Blackwood, 1993; Doyle, Grimm and Thompson, 1993) for a range of livestock and pasture conditions. The Prograze program being run by NSW Agriculture, with support from the Meat and Wool R&D Corporations, aims to improve producers' skills in pasture management.

Pure Swards: simple or a problem?

Management of pure swards is not necessarily easier than mixed pastures. Monocultures of one species tend to be unstable and require continuous intervention to maintain them as no one species is able to completely exploit any given environment to the full. There are always resources available that invading species can use. Pure clover swards can be particularly difficult to maintain, as can lucerne or phalaris pastures where, over time, other species invade and become part of the sward. Options for management in such a sward can, however, be simpler. There may only be one major invading species and it is possible to target grazing to the weak point in that species' life cycle. For annual grasses this could be in late winter/early spring when the plants are just starting reproductive development and are still palatable. Prior rest periods may be required to encourage elongating growth so that the growing points are easily grazed. Grazing practices that encourage growth of, and competition from, the lucerne or phalaris in autumn can also help to reduce germination and establishment of annual species.

Grazing Tools: what are they?

In practice, the tools available to producers for grazing management are the stocking rate, time and duration of grazing and time and duration of rest periods. Stocking rate is arguably the most important (Wilson and Hodgkinson, 1990). In practice, grazing pressure is a better tool than simply stocking rate. Grazing pressure (GP) is the ratio of pasture consumption rate to pasture growth rate (Doyle, Grimm and Thompson, 1993). To influence species composition, at times it is important to limit the ability of livestock to choose what they eat, i.e. GP > 1. At other times it may not matter.

The timing and duration of grazing and rest periods can be critical. Rest periods not only enable pastures to recover and grow faster, but can also bring plants to a developmental state where they are more susceptible to grazing. The aim of a lot of current research is to identify the periods when grazing can have a major effect on common pasture types.

Phalaris Pastures: can we manage them better?

Phalaris is often regarded as the most productive, persistent temperate grass available, a reputation derived from the original Australian cultivar. However, experience suggests that cultivar needs better management as you get closer to the limits of areas where it is adapted. The newer phalaris cultivars do not always persist as well. There are a few reasons for this. The more winter active types, for example, Sirosa, are synchronised in their development which means that more tillers are in a vulnerable stage at the same time (Kemp and Culvenor, 1994). Heavy grazing in early spring when most tillers are reproductive can kill plants. The impact of grazing at this time depends upon soil fertility and pasture growth rates. Where phosphate is adequate and the legume content high, cultivars like Sirosa are better able to cope with heavy spring grazing.

Grazing management of phalaris pastures has several aims:

Maintain phalaris plant densities by not grazing heavily during early reproductive development in spring. This is around October on the tablelands, and a little earlier on the slopes. Average stocking rates may not pose any problems as pasture growth rates usually exceed animal requirements (Kemp and Culvenor, 1994). Spring is the most sensitive time to graze phalaris. Seed growers often have the older phalaris pastures, probably because they do not cut or graze their pastures in spring. The original Australian cultivar of phalaris can be killed by continuous heavy grazing (Hutchinson, 1992).

Maintain the legume content at a reasonable level. On the tablelands, white clover can be maintained in a phalaris pasture by grazing to keep the pasture between 150 and 300 mm in spring (Kemp, Dowling and Michalk, unpublished data). This is best achieved by starting early, just before the spring flush starts and before the pasture becomes rank. There are no problems in animal acceptance of this tactic as the pasture remains green and leafy throughout spring and into summer. Using this approach the legume content was doubled and, even though we did reduce the Sirosa content in the first spring, the boost in fertility from the clover enabled the phalaris to recover such that a year or so later it was over 60% of the pasture. Subterranean clover is not so strongly influenced by phalaris growth in spring. However, pasture growth in autumn does need to be controlled to enable subterranean clover to establish. Direct competition from phalaris plants will limit subterranean clover establishment as will the allelopathic effects of litter (Leigh and Halsall, 1994). Closing phalaris pastures in a good autumn halved the subterranean clover content of the pasture.

Increase winter growth rates. New cultivars like Sirosa are among the most winter active pasture plants. To fully exploit this productivity some form of rotational grazing is required (Kemp and Culvenor, 1994). Research is still in progress, but a six week rest between each grazing may be the minimum to allow pasture growth to increase in winter. Plants should be eaten down at each grazing to encourage tillering. An additional benefit is that this approach helps to reduce the annual grass content (Morley, Bennett and McKinney, 1969).

That phalaris is influenced by grazing management is clearly evident along many roadsides. Phalaris often spreads along roadsides, establishing in competition with mature plants, but not in the adjacent, grazed paddocks. Current work aims to see if we can encourage recruitment of young phalaris plants naturally into poor phalaris pastures.

Barley Grass: can grazing management help control it?

Annual grasses, especially species like barley grass, pose both benefits and costs to agriculture. During winter they can be valuable sources of feed, but in spring become less palatable and their seeds are a health risk as well as causing economic losses in wool and skins. Annual grasses can also harbour diseases that can have severe effects on subsequent cereal crops. In pastures, the annual grasses often crowd out the more useful perennial grasses, lowering production, especially over summer and autumn. In a survey in central NSW, annual grasses averaged around 40% of the pasture in spring (Kemp and Dowling, 1991).

The management of barley grass often aims to reduce its proportion in the pasture and limit the potential seed problems. Two alternative strategies have been developed:

Heavy grazing through winter can be used to consume the forage available and to reduce the height of barley grass. In spring the seed heads can then be below the damage level for lambs (Michalk, Byrnes and Robards, 1976). This approach has worked to some degree and has also caused some reduction in the density of barley grass.

Winter rests and heavy grazing have the effect of reducing tillering in barley grass, allowing reproductive development and plants to be more erect so that growing points can be more easily grazed. Our work at Grenfell in recent years has shown this sequence of events does work (Kemp, Dowling and Michalk, unpublished data). We used a 12 week rest over winter and then grazed the pasture off at the end of August when the barley grass was in the boot stage. This reduced the barley grass population by 50%, similar to that achieved with a herbicide on the same pasture. Seeds germinating in the next year were also reduced by 50%. Results were consistent over three years. The long winter rests are similar to using a long rotation interval between grazings as done in New Zealand block grazing practices (Clark, 1993). We hope to continue this work to determine the better combinations of rest and grazing intervals. We are also exploring the same strategy for vulpia. At other sites where we were not able to graze pastures heavily at the end of the winter rest, the effect on barley grass was much less. An added benefit from the winter rests (long rotation) has been an increase in the clover content of the pasture at all sites where there was no, or little, perennial grass. This makes the pasture more attractive to stock and easier to graze off.

Cell Grazing: where does it fit?

In recent years there has been an increase in interest in Cell Grazing, sometimes called Time Control Grazing (TCG). This approach to grazing was developed by Savory (1988) in southern Africa, based on earlier ideas of Voison (1960) and was initially applied in semi-arid environments. More recently, the same approach has been promoted in higher rainfall environments across southern Australia. TCG is frequently promoted as a grazing management system, but in effect its promoters are offering a whole farm management system which combines some changes in grazing practices with a large amount of animal, financial and business management (Hacker, 1993). This has created some confusion as to what TCG is all about.

Many producers have probably benefited from adopting TCG, but those benefits may not have come directly from a change in grazing practices, rather, better organisation and financial advice may have been more important. Adoption and promotion of TCG has also meant that many producers are taking more notice of what is happening to their pastures. Their response to changes in their pastures has then improved and problems addressed earlier. A worthwhile part of TCG is the establishment of goals for resource management and then monitoring progress towards those goals. Where stocking rates are near the limit for a pasture, under current practices TCG may not result in any improvement in carrying capacity.

I will confine my comments on TCG to the grazing management components and in particular to the general patterns of stock movement which seem to be commonly followed. TCG is based on a theory about pasture growth and development that has been extensively reviewed (Hacker, 1993; Hutchinson, 1993). The main points that have come from those reviews of TCG theory are that there are not a lot of data to back it and that, while benefits can arise from producers using TCG, they are not predictable. There is also concern that some components of the theory, for example the herd effect, may be damaging to some soils and pastures. Simple theories about succession do not apply very well in practice as is evident in the debates on condition and trend by range managers. The role of legumes does not receive much consideration, which is disappointing given their importance in Australian agriculture. Producers though, do not need to adopt all aspects of TCG.

The common patterns of grazing used in TCG require the establishment of a cell. That cell should, ideally, contain 15-30 paddocks. Stock are amalgamated into larger mobs and move around the paddocks in sequence. The rate of stock movement depends upon pasture growth rates. The slower the pasture growth, the slower the rate of movement. This often means that in poor seasons the interval between grazing paddocks can be 90 days or so, and that stock graze each paddock for 3 days at a time, assuming 30 paddocks. In spring, the grazing period may be one day and intervals down to 30. Paddocks can be dropped in and out of a grazing sequence depending upon seasons. Paddocks can be set up so that the grazing interval is similar in each, allowing for variations in pasture quality and productivity.

Producers using TCG can get a better appreciation of how the season is going as the next paddock in a sequence is usually the longest rested. They can see how much feed is in front of them. Periods of rest also allow the species in the pasture to grow such that the composition of a pasture becomes more apparent. Producers do get a better appreciation of what they have.

Problems may arise with TCG at lambing or calving times with continual movement of stock. More planning may be required to decide on lambing and weaning paddocks. Rapid movement around pastures and light grazing during spring may result in under-utilisation of the available forage. This may help the perennial grasses to survive, but could also increase the annual grasses and reduce the legume content.

Producers considering TCG need to do so with an open mind. There are parts of the package, as currently marketed, that are of benefit. However, other parts are not predictable in terms of their outcomes. Assuming that the herd effect and simple succession will work could lead to problems. However, the grazing patterns used by TCG over autumn and winter are in line with data on better management for perennial pastures (Kemp and Culvenor, 1994) and similar to practices developed in the controlled grazing systems (Clark, 1993). The need to continue rapid rotations throughout spring and summer is open to question. All paddocks may not need to be treated in the same way.

We would suggest that more attention needs to be paid to the species in a paddock and that opportunistic and tactical approaches be used to exploit the diversity between paddocks. We suspect that producers adopting TCG will evolve their own systems in such a direction.

Animal Species: what advantages have they?

Sheep, cattle and goats are the main domestic livestock available to producers for grazing management of their pastures (Allan, 1994). Sheep are more selective than cattle and this can mean they remove more desirable species when given the ability to choose what to eat. On the tablelands cattle pastures often contain more clover than those grazed by sheep. Judicious use of cattle and sheep can help to maintain pastures. This is the subject of current research at Tamworth and Hamilton. The differences in selectivity suggests that more intensive management could be required for sheep than for cattle to sustain a desirable composition in pastures.

Goats are well known for browsing, preferring more fibrous plants over legumes. The complementary nature of grazing by goats and sheep is often used to advantage. A few goats in a flock of sheep do not influence the production from sheep, but are able to clean up many of the

weeds. Recommendations on the proportion of goats are available (Allan, Holst, Campbell, 1993). An important point is to use a few goats often rather than waiting until you have a major weed problem that would require a large number of goats to control. Some deer also prefer to browse and this could be exploited in the future.

Herbicides: do they have a place?

Herbicides clearly have a place in managing pastures. They are often cost effective and help solve problems that grazing or other practices cannot (Beattie, 1993). In the cropping zone herbicides are almost mandatory to clean up pastures prior to a crop, especially to remove annual grasses and minimise disease risks. Herbicides do, though, reduce the amount of forage available for animals. In some instances this forage could be consumed by livestock and converted into wool or meat. By utilising this forage, weed control can be achieved. Opportunities to use grazing instead of herbicides should always be considered. Our work with barley grass at Grenfell suggests that it may be more practical to control this species by grazing during the pasture phase, using a herbicide as a final clean-up in the last year before cropping again.

Hay and Silage: does it help?

Fodder conservation can be an important way to manage the forage supply to livestock (Kaiser, 1994). Hay and silage cuts can also help in the management of pastures, as many producers know. Anecdotal evidence is fairly common about how a forage cut dramatically cleaned up a pasture. Silage cuts can be more useful and less risky than hay as they are often taken earlier

in the season before there is much mature seed from weed species and the material is quickly removed. Pastures take longer to recover from a hay cut and the shading that occurs as material dries.

The cost of fodder conservation has often been considered as an impediment to making more hay or silage. However, the beneficial effects on pastures are often ignored in these calculations. A silage cut could easily replace the cost of a herbicide application for weed control.

Fodder conservation is best integrated with other aims. Producers in Tasmania and Western Australia who have adopted the New Zealand block grazing system (R. Young, 1993; J. Young, 1993) often use fodder conservation to help manage pastures and to transfer forage from the spring to late autumn. Once the autumn break actually occurs they then feedlot their stock in small paddocks to allow the rest of the pastures to grow and produce more forage before starting their rotation over winter. They have claimed that by doing this they have fed less forage during the year than they used to.

Grazing Management: practice?

Grazing management is one of the tools readily available to producers to sustain productive pastures. Many producers practice some forms of grazing management, though information is not always available to help them decide on the better tactics. The experience of producers and current research is being pooled at present in a large program funded by the Meat Research Corporation with additional support from Wool and the Land and Water Resources R&D Corporations. One aim is to determine the better practices to recommend for the main perennial pastures in the higher rainfall zone. Those results will not be finalised for a couple of years and hopefully will not be delayed by the current drought.

When is it most important to consider grazing management practices? In general the greatest impact will occur when pastures are actively growing. Animal production is also very dependent on the amount of green forage available (Willoughby, 1959). Desirable species need to be able to grow to be competitive against less desirable plants. In the short term, management that enhances vegetative growth can have a big impact on the proportion of a species in the pasture. In the longer term it is important to encourage changes in plant density so that the desirable species maintain dominance. Management during periods of critical feed supply can also be more important than during periods of abundance. The productivity of many pastures is likely to be very dependent on management from the autumn break until late winter.

Like many other practices, grazing management becomes a learned skill. You cannot learn all overnight and it is better to proceed cautiously. Not all paddocks will need a change in management to sustain them. Concentrate on those paddocks where there is some chance for improvement and where you can use grazing to help. Over time the practices that suit you, your livestock and your pastures will emerge. The better returns may come from better quality persistent pastures before animal production can be improved. Be flexible and consider the needs of the grazed as much as the grazer.

Acknowledgements

The ideas in this paper have benefited from many discussions with colleagues over the years, especially Drs David Michalk and Peter Dowling. Funds for the research outlined have been provided by the Australian Wool Research and Promotion Organisation and the Meat Research Corporation.

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