Pasture and grazing management
Stocking rate is a major determinant of profitability. To optimise profitability the objective is to maximise the number of livestock carried at the least cost per livestock unit. This can be done by either:
- Growing more pasture during the times of year when feed is limiting (usually autumn/early winter in southern Australia) and running more livestock at the same level of efficiency, or
- Growing the same amount of grass and improving its utilisation by running more livestock more efficiently, or
- A combination of both
Growing more pasture
During winter in southern Australia, pasture growth is mainly limited by temperature. However, the level of soil fertility, the type of pasture species/varieties present and the way the pasture is grazed all have a major impact on the pastures growth rates at this time of year. These factors influence the length of the growing season and how quickly the pasture responds after the autumn break or after drought. They also impact on the quality of the pasture.
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Utilising more pasture
How much pasture you can utilise is essentially driven by stocking rate. However, your management calendar (time of lambing or calving, time of sale of lambs or culls) also impacts on how well you can match pasture supply with the feed demand. For breeding flocks or herds it may only be possible to utilise 50-60% of pasture grown. Some pasture must be left at the end of the growing season to provide feed for stock over summer/early autumn, provide litter for the soil biota and to protect the soil from erosion. The greater the variability in pasture production from year to year, the more difficult it is to achieve high levels of pasture utilisation. The only exception would be for those businesses running livestock trading enterprises.
The Mackinnon group provides an on-farm consultancy service and can advise you on:
- Soil testing and fertiliser programs
- Grazing systems
- Pasture renovation
- Selecting an optimum time of lambing /calving
- Optimising stocking rate and managing risk
Fertiliser is essential to maintain productive and persistent improved pastures. Responses in pasture growth and stocking rate from fertiliser applications can be in the order of 30-150%, depending on soil fertility and the species present.
Fertiliser can represent a large annual cost - so it is critical that fertiliser decisions are economic. The first step is to take soil tests and have them analysed by an ASPAC accredited laboratory. This will give you the objective information to make rational decision about what your paddocks require.
The most common macro nutrient deficiencies in sheep and beef pastures are phosphorus (P), sulphur (S), potassium (K). The trace element molybdenum (Mo) is deficient on acid soils and needs to be applied once every 6-7 years. A soil test will indicate the P, K and S levels in the soil. Soil nutrient targets are shown below. Also request the laboratory to provide you with a phosphorus buffering index (PBI). Note: The need for trace elements should be determined by conducting a plant leaf analysis not a soil test.
Phosphorus (Olsen method)
Potassium (Skene method)
150 mg/kg (light soils)
220 mg/kg (medium soils)
300 mg/kg (heavy soils)
Sulphur (KCl40 method)
* Targets are for improved pasture species. Native perennial grasses are adapted to lower levels of soil fertility and will be out-competed by exotic species as soil fertility increases. To protect native grass based pastures, fertilise at lower rates just to maintain some subclover (eg. 10-20% of the composition).
Capital applications of fertiliser are aimed at lifting the soil nutrient levels to target levels based on optimising growth and persistence of improved pasture species. They involve making one or more applications over and above the amount required to replenish nutrients lost through the export of farm products. Capital applications often involve phosphorus but can refer to lime. How quickly you build up nutrients will depend on cash flow/access to capital and how quickly you can build up stock numbers to utilise additional pasture grown.
Maintenance applications of fertiliser are aimed at replacing the amounts of nutrients exported off the farm in produce (meat, wool, hay, silage) or tied up in the soil. These applications are designed to maintain the target soil levels for each nutrient and maintain the current level of productivity. Maintenance rates of P are based on the phosphorus buffering index (PBI) of the soil. For example: apply 0.8 kg P/DSE when PBI is low (0-100), apply 1.0 kg P/DSE when PBI is moderate (100-300) or apply 1.2 kg P/DSE when PBI is high (greater than 300).
Role of Nitrogen
Nitrogen should be considered as an alternative supplementary feed, rather than as a regular part of your maintenance fertiliser program. Nitrogen (N) can be used to boost winter pasture growth rates and reduce the need for feeding supplements. The best nitrogen responses occur in improved pastures with good soil fertility. Typical winter pasture responses to N range from 5-15 kg dry matter (DM)/kg N applied. The decision to apply N to pasture or feed grain, silage or hay will depend on the relative prices of the options at the time. In most circumstances, N application works out to be a cheaper option on a cents/kg DM and cents/MJ ME basis.
The way a pasture is grazed has a large impact on pasture growth rates, pasture composition, persistence of perennial grasses and how evenly the pasture is eaten by stock. Victorian research indicates that resting a perennial grass based pasture via some form of rotational grazing, rather than set stocking, can enable an increase in stocking rates by 10-20%.
The way the rotation is managed gives different results:
- A rotation which rested the pasture for 6 weeks in autumn, winter & summer, and 3 weeks in spring (but allowing each paddock to be grazed for 2 weeks at a time) gave a 10% stocking rate benefit compared with set stocking.
- A more flexible rotation, which rested the pasture for 4-6 weeks in autumn, 6 weeks in winter, 3 weeks in spring and 10 weeks in summer, but reduced grazing time to 3-4 days in each paddock, gave a 20% stocking rate benefit compared with set stocking.
Capturing the benefits
Modifying your current grazing system is an area where you can get pasture growth and stocking rate benefits at relatively low cost. On most farms there is an opportunity to use your existing infrastructure (paddocks, water supply) to get noticeable improvements.
Improved weed control is another benefit from improving grazing management. This will reduce herbicide use and costs.
Sowing improved species of clovers or grasses or more winter active cultivars will increase seasonal and total pasture growth. This option also represents a large capital cost of $150-300/ha depending on inputs required. Sowing pasture can be profitable but certain criteria needs to be met to guarantee this. The criteria are:
- Contain the capital costs of establishment - Get it right the first time. This requires careful planning and preparation at least 12 months before sowing. Choice of species and cultivars suited to your climate and soil types is critical. The Grassland Society of Southern Australia has a data base of currently available pasture cultivars and the conditions to which they are suited.
- Ensure the pasture persists - The shorter the life of the pasture, the shorter the time you have to get your money back. Your fertiliser and grazing management will affect how long a perennial pasture persists.
- Increase stocking rate - How many extra stock you need to run will depend on the two factors above. The shorter the pasture's life the higher the stocking rate or the higher the enterprise gross margin $/ha needs to be to get your money back. Sowing short-term pastures (eg. Italian ryegrass) or fodder crops will not be profitable if significant lifts in stocking rate cannot be achieved or if they cannot provide the feed at a lower cost than other supplements like grain.