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Bulletin 4690
Geoff Moore, Paul Sanford and Tim Wiley
Perennial pastures for Western Australia is designed to become n essential tool for producers in agricultural areas, farm advisers, agribusiness and students.
In 250 pages it covers all perennial options from herbaceous legumes to temperate and sub-tropical grasses, herbs, fodder shrubs and salt land pastures.
The comprehensive descriptions, information on current and potential uses, establishment tips, soil and climate requirements, management and other details are also accompanied by great colour photographs.
Chapter 1
1.1 Why perennial pastures?
There is a strong interest in perennial pastures due to the growing realisation that farming systems based solely on annual crops and pastures are not sustainable in many regions of south-western Australia. Environmental and management issues facing agriculture include: rising groundwater and the spread of salinity; herbicide resistant weeds; soil acidity and; wind erosion. Perennial pastures offer a sustainable and profitable alternative in many areas.
Potential production benefits from perennial species include:
- ut-of-season green feed.
- Increased carrying capacity due to improved seasonal distribution of feed and pasture use.
- Ability to reduce or replace supplementary feeding in autumn.
- Ability to increase production from land with a low carrying capacity.
- Ability to turn-off animals at target liveweights all year round.
- Reduced wool faults and maintenance of wool fibre diameter and staple strength.
- Reduced fodder conservation.
- Increased winter feed.
- Opportunity to rest annual pasture paddocks after the break of the season.
Soil conservation benefits include:
- Increased water use and reduce deep drainage to groundwater.
- Maintenance of plant cover in summer to reduce wind erosion.
- Increased perennial cover for waterways.
Stock grazing green feed all year round - is this possible or simply a pipedream in Western Australia with its strongly Mediterranean climate? As recently as 5-10 years ago, most people would have thought the latter. However, innovative producers have lead the way in demonstrating that the large scale planting of perennial pastures are a viable alternative. Some producers are even close to achieving the goal of stock grazing green feed all year round.
While there is still a long way to go, there has been a change in attitude to growing perennial pastures, which in years to come could result in large areas of the rural landscape in WA being transformed. Annual pastures are the main component of grazing systems in WA and will continue to remain that way. Most perennial pastures are a mix of annual and perennial species, with the dominant component varying with the season.
In general, perennial pastures are still a minor component of grazing systems but several economic options have been developed for different parts of the landscape. By selecting species that are compatible with the physical environment (soil, climate) and the farming enterprise, some of the least fertile and most fragile soils can be transformed into productive, sustainable areas with an increase in farm profit and reduced land degradation.
- Alleys of tagasaste have transformed some of the poorest, deep-leached sands into productive paddocks. Tagasaste provides out-of-season green feed and increases carrying capacity, while also reducing wind erosion and deep drainage.
- Warm season grasses with companion annual legumes are turning waterlogged land that was previously over run with reeds into some of the most productive and profitable pasture paddocks in the State.
- Phase farming with lucerne is creating sustainable and profitable rotations with annual crops in medium and low rainfall environments. The area of lucerne increased from ~5,000 ha in 1995 to about 170,000 ha in 2001.
- Alleys of saltbush are being used strategically to keep highly saline groundwater at depth, allowing productive non-halophytic pastures to be grown in the inter-row.
- Perennial pastures are enabling an increase in stocking rates and are reducing land degradation on large areas of sandy soils susceptible to wind erosion on the south coast.
The impetus for the increased interest in perennial pastures in WA has largely come from innovative farmers and farmer groups such as Evergreen Farming, the WA Salt land Pastures Association, the Western Australian Lucerne Growers and regional grower groups.
These groups have played a major role in the promotion and the widespread, on-farm testing of perennial pastures. It has been dynamic individuals largely from within these groups who have demonstrated the full potential of perennial pastures. These producers have mastered the practical aspects of successful establishment and management and then captured the benefits of perennials in new farming systems. They have transformed the landscape of their farm and translated the production benefits of perennials into whole-farm benefits by developing more sustainable and profitable farming systems. However while these innovative producers lead the way in the integration of perennial pastures on-farm, they are still a minority.
New farming systems will develop over the next decade which continue to challenge traditional conventions as innovative producers strive to improve their medium- to long-term sustainability. New species and varieties of perennial pastures will be developed to expand the options available to producers.
Potential new species and cultivars that could be available within 5-10 years and which will significantly increase the area sown to perennial pastures include:
- Acid tolerant lucerne varieties.
- Grazing tolerant lucerne varieties developed for southern Australia.
- Perennial herbs like chicory, with new varieties developed specifically for southern Australia.
- New perennial legumes like sulla and perennial Lotus with desirable attributes such as condensed tannins.
- New, warm season grasses specifically developed for southern Australia.
Some producers may have concerns about the potential negative effects from growing perennial pastures. A range of these issues are discussed in Table 1.1.
With this publication, we aim to help producers and farm advisers make well informed decisions about perennial options - where to grow and not to grow different species, how to successfully establish and manage perennial pastures and how to integrate them into the farming system.
All the perennial pasture options both currently available and those being developed are discussed including a few which are not recommended because of the associated environmental weed risk. The weed potential of these species has been flagged.
Table 1.1 Negative effects of perennials - are they perceived or real?
|
Perceived negative effect |
Discussion |
|
Risk of establishment failure or of poor establishment. |
'The most expensive pastures are those that fail to establish'. In general, perennial pastures are more difficult to establish than annual crops and pastures. Seedling growth is relatively slow compared with annual species, so good control of annual weeds is essential. However, proven methods of establishment with a high success rate are now available for most perennial pasture types. Ensure all of the steps for successful establishment are undertaken to minimise the risk. Last minute decisions to sow perennial pastures can be expensive if the necessary paddock preparation has not been carried out. |
|
The perennial pasture establishes well, but subsequently fails to survive if there is a dry summer. |
Well-adapted perennial pastures have proven highly drought tolerant. Ensure that the most suitable species are selected for the environment (soil, climate) and that all of the factors for successful establishment are undertaken. Perennial plants need to develop a sufficiently large root system in the establishment year to survive the first summer. Excellent weed control during establishment is essential. Even when perennial plants survive weed competition during establishment, the result is smaller plants at the start of summer that will struggle to survive if there is a prolonged summer drought. |
|
Do perennial pastures have more management requirements than annual pastures? |
Most perennial pastures require some form of rotational grazing to persist and be productive in the medium- to long-term. Rotational grazing of annual pasture paddocks can significantly increase pasture production and utilisation. Compared with the set stocking of annual pastures, there will be additional stock movement required with perennial pastures but this is more than off-set by the reduced need to supplementary feed stock in autumn. |
|
Perennial pastures exacerbate problems with worm control in sheep. |
This is not necessarily the case, as perennial pastures can change the dynamics of the worm population. There is reduced selection pressure for resistant worms as non-resistant worms can survive summer on perennial pastures. As a result, the worm count is sometimes higher on perennial pastures, but the proportion of resistant worms may be lower (Section 2.4). |
|
Perennial pastures become difficult weeds to control in crops. |
The main perennial pasture species that are likely to be weeds in crops are lucerne, which is often grown in a phase rotation with crops, and kikuyu, which can be spread by stock in dung. A low density of lucerne plants in a cereal crop can adversely affect crop yields. Methods for successfully removing lucerne before the cropping phase have been developed (Lucerne - Section 3.4). Most perennial grasses are established as permanent pastures and the risk of spread around the farm is negligible. However, kikuyu can be spread by stock, so stock movement from kikuyu pastures into paddocks that will subsequently be cropped should be controlled. |
|
Perennial pastures produce less feed than annual pastures. |
Total dry matter production from well-managed annual and perennial pastures is usually comparable but perennial pastures have a more even seasonal distribution of dry matter production. The term 'perennial pastures' is somewhat of a misnomer as most perennial pastures are a mix of perennial and annual species. At certain times of the year, the annual species may be the dominant component of the pasture. Overall production can increase with a perennial-annual pasture, or at the least should be similar to a good annual pasture but with a better seasonal distribution. Spring production from annual pastures is often higher than for many perennial pastures but perennial pastures are more productive in summer, autumn, and/or winter (depending on species and period of active growth) - when feed is often limiting. Consequently, each unit of production is more valuable than the same production in spring when there is a surplus of feed resulting in poor pasture utilisation. |
|
The 'green bridge' created by perennial pastures increases the incidence of pests and diseases in annual crops and pastures. |
Perennial pastures do provide a 'green bridge' that can assist viruses and other pathogens to persist over summer. This risk can be reduced by only sowing virus-free seed and manipulating grazing to minimise potential problems. The risk of 'green bridge' is reduced for diseases that are carried only on green foliage, as the seasonally dry conditions, which often extend from late spring to mid- to late autumn, ensure a substantial, continuous bridge of green foliage is rarely present away from isolated 'wet' areas (Section 2.5). |