Sown pastures in Queensland: their place, their role and the things to watch
Sown pastures can offer flexibility in your beef enterprise and can provide solutions for land degradation problems but you need to carefully consider the benefits and be aware of some of the pitfalls. In most situations it is not economical to replace a productive native pasture with a fully sown pasture.
What are sown pastures?
There are several definitions of sown pastures. The most easily recognised type of sown pasture is the fully sown pasture or ‘improved’ pasture. This type of pasture development usually involves removing the existing vegetation, preparing a seedbed and sowing exotic grasses and legumes. This is often referred to as ‘high input’ pasture development.
The other major form of sown pasture development is where perennial legumes are ‘oversown’ into an existing native pasture and is often referred to as a ‘low input’ development option.
Ley pastures and browse legume forage systems are unique forms of sown pasture development. Ley pastures are used in rotations in cropping situations to help restore soil fertility and structure and to break disease cycles. Ley pastures are relatively short-term (two to five years) and are restricted to cropping lands. Leucaena is grown as a browse legume forage system.
For the purpose of this page we refer only to the high input development option of a fully sown ‘improved’ pasture.
What are the benefits of sown pastures?
The benefits of sown pastures include:
- improved pasture productivity
- management flexibility
- land rehabilitation
In the short- to medium-term, sown pastures can be more productive and have a higher carrying capacity than native pastures. Sown pasture species often provide higher quality feed and have a longer growing season than native pastures. The combination of improved quantity and quality of pasture can result in more cattle gaining more weight for longer.
Special-use sown pastures offer management flexibility. They can be used to finish sale cattle earlier than can be expected on native pastures and allow for the separate management of different classes of stock such as bulls, weaners or first calf cows.
Sown pastures can also be used for rehabilitating degraded pastures and often provide an option for weed management by providing vigorous pasture competition. They can be used to strategically spell native pastures.
What are the potential problems with sown pastures?
There are three major potential problems with sown pastures:
- risk of failed establishment
- pasture run-down
Establishing a fully sown pasture is not cheap. Major costs are associated with owning and operating tillage and sowing equipment and purchasing seed and fertiliser. Other costs can include herbicides and legume inoculant. To enable establishment and seed set, the pasture should not be grazed for several months after sowing. Therefore, this immediate loss in cattle production that needs to be taken into account.
Environmental conditions influence establishment. There is always a risk of failed establishment due to dry conditions following sowing. Heat wave conditions can seriously damage establishing pasture seedlings and early frosts can prevent seed set in late sown pastures.
The major restriction for the cost effectiveness of sown pastures is that the benefits in terms of pasture productivity are not sustained. This is known as pasture ‘run-down’.
When land is first cultivated, a lot of nitrogen that has been present in the soil in a form unavailable for plant up-take is released. As a result the sown pasture receives a boost known a pasture ‘run-up’. However, over time much of the available nitrogen once again becomes locked up in a form that is unavailable to the plant and pasture productivity declines.
Generally, the higher the inherent fertility of the soil the slower the run-down. In the run-down situation, most exotic grasses are no more productive than the natives, and in fact, are less competitive than the natives and often disappear. Run-down of sown pastures can take up to 20-30 years on a fertile brigalow soil or just two years on an infertile sandy soil.
So do I use sown pastures or not?
Before rushing into a pasture development program you should consider:
- The need for the sown pasture (what purpose will it serve)?
- The availability of suitable country.
- The availability of suitable farming and sowing equipment.
- How long-lived are the benefits?
- Ongoing pasture management requirements.
- Are the benefits economic in both the short and long terms?
You need to be clear about the intended purpose of the sown pasture and have realistic expectations as to how long the benefits can be sustained. Simply sowing an exotic grass pasture into breeder country is unlikely to turn it into top class finishing country. However, if you have some country that is reasonably fertile, such as a large creek flat or old scrub country, and you intend to use a sown pasture for finishing sale cattle, then it is likely that the sown pasture will provide an economic return.
Another consideration is the availability of suitable equipment to establish the pasture. You’ll require farming equipment such as off-set discs or a tyne implement for the land preparation, a fertiliser spreader, seed drill or seeding drum for sowing the pasture. It may be more cost-effective to use a contractor rather than purchase equipment.
How you prepare for and manage a sown pasture largely determines its establishment, longevity and productivity. The pasture run-down described above is inevitable but the rate at which the pasture runs down can be managed by sowing recommended pasture species and through careful pasture management. Grazing management and/or fertiliser application to maintain the legume component will slow the run-down. Renovating the pasture with a tillage implement may also temporarily increase pasture productivity by releasing some of the soil nitrogen that has become ‘locked up’. Generally, the more you put into a sown pasture, the more you are likely to get out of it.
For a fertile land type where run-down occurs slowly an alternative is to accept the run-down and adjust stocking rates in accordance with the reduced carrying capacity to maintain individual animal performance. In either case it is necessary to consider the cost of managing run-down in the economic analysis prior to sowing the pasture.
Only consider sowing a pasture when the potential benefits, in terms of improved productivity, outweigh the costs of establishment and run-down management. In most situations it is not economical to replace a productive native pasture with a fully sown pasture.
- Sown pastures offer flexibility in your beef enterprise and can provide solutions for land degradation problems.
- Sown pastures can be expensive and risky to establish and their productivity and persistence often declines due to pasture run-down.
- Clearly define the intended purpose of the sown pasture and critically assess land development potential.
- Use recommended grass and legume species and appropriate sowing techniques and equipment.
- Be aware of, and be realistic about, the costs associated with pasture maintenance.
- Carefully consider the benefits and risks of sown pastures long before you put fuel in the tractor or seed in the planter.
Bill Schulke, formerly Queensland Government.