SUSTAINABLE PASTURE MANAGEMENT
In the past, pastures were managed with the aim of achieving maximum plant growth and productivity. This is increasingly changing. The primary aim today should be to care for the plants and the soil; and in turn the grazing animals needs are better met by improved soils and plant productivity. Sustainable pasture management depends upon a good understanding of the biological processes involved in pasture growth and health. Ideally it involves:
- Observing the factors that affect the condition of a pasture, i.e. soil, plants, animals, weather patterns, etc.
- Influencing the factors that affect the condition of a pasture to curtail any degradation. For example, if soil condition is deteriorating, fertiliser may need to be added, or the number of animals grazing may need to be reduced. If growing conditions for plants are becoming strained, the number of animals per hectare should be reduced.
Sward dynamics is the study of growth responses to different grazing management practices. Most sward dynamic research has been confined to common cool temperate pastures (e.g. perennial ryegrass and/or white clover) growing in relatively uniform climates such as England or New Zealand. There is only limited information available about how pastures respond to different treatments in warm climates, unpredictable climates, or with less common grasses (eg. native pastures in Australia). Given the lack of solid information, sustainable management in many pastures may require close observation coupled with a degree of caution.
SUSTAINABLE PASTURE VARIETIES
Understanding and managing pasture is highly complex. Pastures differ in terms of both the mix of plants of which they are composed, and in the way those plants grow (ie. general plant health and vigour). For effective grazing, the pasture needs to match its use: the number and type of animals being grazed should be appropriate.
Some of the more important pasture varieties in Australia are:
- Grasses: Rye grass, Fescue, Cocksfoot, Kikuyu, Paspalum, Phalaris, Prarie Grass, Sorghum, Oats
- Legumes: Lucerne, Clovers, Vetches, Lotus, Sainfoin
- Other Plants: Saltbush, Chicory
Saltbush is particularly useful in salt-affected, arid or semi arid areas. It is a very nutritious fodder plant. Compared with seaweed (often used as stock feed supplement), saltbush is higher in most nutrients, including iodine.
Its value as a stock feed is considered comparable to or better than most other feeds including clover pasture, green or dry grass pasture, barley, oats, silage or lucerne. With the exception of lucerne, saltbush is around 28% above most other pasture species in dry matter.
Saltbush also appears to have some health effects for livestock. Sheep grazed on saltbush appear to have fewer health problems. It appears high in sulphur (a characteristic shared by garlic). This may suppress both fungal and pest complaints within the body.
At Narromine in N.S.W., a property is planted with saltbush (on 2 m x 4 m spacing) then later seeded with pasture mix of lucerne, snail medic and Bambatsi makarikari grass. This treatment has been shown capable of increasing the stock carrying-capacity fourfold, largely because saltbush can survive much better during dry periods.
At Donald in Victoria, a property planted with saltbush is used for grazing goats. Plants are on a 1 m x 1.25 m spacing, planted in late autumn. Here, goats are let onto saltbush for 1-2 hours then removed to another paddock for remainder of the day. Even when plants are eaten back very hard, they still recover, irrespective of whether it rains or not!
The main varieties used in farm situations are:
- Atriplex nummularia – old man saltbush
- Atriplex vesicaria - bladder saltbush
- Atriplex semibaccata - creeping saltbush
- Rhagodia hastata
- Rhagodia linifolia
- Chenopodium triagulare
Atriplex is the saltbush of the black soil country and forms the most important genus. Rhagodia species have succulent fruits. Chenopodium favour the sandy and light-red soils.
Reference: Farm Management by John Mason. This book has an excellent chapter on pastures.
HOW MUCH GRAZING?
Overgrazing can be a serious problem resulting in:
- An increase in weeds
- A change in relative proportions of pasture specie
You must watch the animals on a pasture and move them or provide supplementary food before overgrazing occurs. Pastures will, however, respond to heavy grazing followed by a period of rest. It is like pruning a rose or fruit tree: removing part of a plant will promote a flush of new growth.
Management of grazing requires an understanding of the following terms:
- Pasture Mass - Measured as kilograms of dry matter per hectare (Kg DM/ha).
- Occupation Period - When different groups of animals are using the same paddock, this refers to the combined length of time that the paddock is grazed per rotation.
- Period of Stay - Length of time a group of animals is left in a paddock, per rotation.
- Recovery Period -This is the period that the pasture is left without being grazed - commonly 12 to 50 days in reasonably fertile, well watered, temperate climate pastures.
HOW LONG TO GRAZE?
The big question is: when should animals be grazed on a particular paddock, and for how long? Various formulae have been devised to calculate answers to this problem. Stocking rates are commonly stated in terms of 'Dry Sheep Equivalents' (DSE). This is affected by many factors, including rainfall, recovery periods (in turn affected by type of pasture species) and soil fertility.
In South Australia R.J. French developed a system for determining DSE based upon rainfall. An example of one way this system might be applied gives a potential stocking rate of 1.3 DSE per hectare for each 25 mm of annual rainfall which exceeds 250 mm.
Potential stocking rate = Annual rainfall in mm - 250 mm)
25 x 1.3
Principles to Follow When Resting a Paddock
- Paddocks growing nitrogen-fixing plants (eg. legumes) should be fallowed with nitrogen users such as grasses.
- Grow a weed-suppressing crop in a paddock which just finished with a relatively non weed competitive crop.
- Alternate cool and warm season growing plants in a paddock.
- Allow an adequate period between repeat plantings of the same type of crop in a paddock, so pest and disease problems can die out (for most crops, three years is adequate; for some, longer may be preferred).
- Grow shallow-rooted plants in an area to follow deep-rooted plants.
- Alternate higher and lower users of water.
- Follow heavy feeders with light feeders.
- Use weed-suppressing plants periodically where possible (eg. sorghum and oats).
- Use pest/disease-suppressing crops periodically where possible and appropriate (eg. garlic for fungal diseases; marigolds for nematodes).
- To maintain the vigour of native pasture species, follow the general rule of "Graze half and leave half" (i.e. allow no more than 50% of the leaves to be removed, then move stock elsewhere).
The two main methods of grazing management are continuous or rotational.
Here animals are left in the same paddock throughout the entire growing season (they may be moved elsewhere over winter, or when it is time to sell).
- This works well in areas with dependable climate (eg. England).
- It is not appropriate when growing conditions are variable (eg. areas that have spurts of growth, or dry and wet periods).
- It is not suitable in pastures containing a variety of species with different growth rates - some species can be over-grazed, and others under-grazed.
Research has shown that overgrazing is not related so much to the number of animals in a paddock; rather it is affected by the time the animals spend in the paddock. Rotational grazing is usually preferable for farm sustainability.
- It has sometimes has involved rotating a herd between several paddocks, ignoring the status of pasture in each paddock - sometimes under grazing, sometimes overgrazing.
- This method should be used to minimise over-grazing and under-grazing.
Voisin Grazing Method
Voisin was an academic and scientist in France who devised a grazing method that interferes minimally with the pasture environment.
The concept involves dividing a pasture into small paddocks and rotating animals through them. The rate of rotation is dependant upon growth rate of pasture plants, and the pasture mass.
The aim is to keep plants as close to the peak of their growth curve as possible. Pre and post grazing pasture masses are estimated for each paddock, and this then forms a basis for deciding when to move animals on to the next paddock.
Problem: When animals are given a greater choice for grazing they can become selective; hence certain plants in the pasture can be eaten out and disappear, while other less-favoured species remain relatively untouched.
Answer: Restrict animals to a small area and they become less selective about what they eat, so the area can be grazed more evenly.
OTHER AREAS FOR GRAZING
During drought or other difficult periods, extra temporary grazing may be found on public land or other sites in your locality.
Roadsides often provide extensive areas of suitable foodstuffs for stock. In areas where remnant vegetation is scarce there may be long stretches of grass suitable for cutting as hay, or for grazing stock on. Grazing such areas has the added advantage of reducing fire risk by reducing fuel loads. It may have a detrimental effect on any small patches of remnant vegetation that may still exist, particularly if the vegetation is very palatable for your stock.
Control of stock is critical!
- They should not impede traffic or create a safety risk (eg. risk of car accidents).
- They can be controlled by temporary electric fencing, but this should be regularly checked, or by being herded at all times (eg. by stockmen and dogs).
It is important to check local regulations regarding roadside grazing. You may require a permit, or it may not be allowed at all. Consider the damage that may be done to the public of vehicles if an accident should occur.
In some states established droving routes have been gazetted in state legislation. Regulations governing grazing on these reserves should be checked out before contemplating such grazing.
As with stock on your property, it is very important that stock grazing on roadsides have access to a suitable water supply. Access to such supplies should be controlled to prevent damage to the supply and its surrounds.
In some areas it may be possible to obtain permits or leases to graze public land. These may be temporary (eg. as a means of reducing fire risk) or ongoing. Check with your local Department of Agriculture or Land Management to see if this is possible in your area.
Commercial Timber Plantations
Large pine and hardwood plantations may have areas of grass (eg. between rows) large enough for grazing. It may be possible to obtain permission from plantation managers/owners to graze these areas. (This practise helps them by reducing fire risk and competition for their trees.)
Council approval is needed.
Industrial Areas (Around Factories)
Consider any approval needed from local council or factory owners. Some factories allow agistment on the surrounding fields as this reduces labour and costs for slashing. Caution is needed to ensure that no toxic waste which may harm animals is dispersed onto the land.
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