Phosphorus for Pastures
Phosphorus for Sheep and Beef Pastures
Farm profitability is linked closely with the correct use of fertiliser.
To make the phosphorus fertiliser decision for Victoria sheep and cattle producers easier, we have combined the results from the Long-term Phosphate Experiment at Hamilton with a fertiliser decision method developed in New Zealand.
This publication assists producers to:
- decide how much phosphorus to apply to particular paddocks
- decide what type of phosphorus fertiliser to use
- plan a soil phosphorus monitoring program
- decide which paddocks have the greatest need for fertiliser
The key message of this publication is that the old rule of thumb of one kilogram of phosphorus per dry sheep equivalent can be greatly refined to improve profitability, and minimise environmental impacts.
Research indicates that the amount of phosphorus per dry sheep equivalent (kg P/DSE) needed to maintain productivity varies for 0.42 to 1.46 kg P/DSE depending on rainfall, soil type, pasture species and grazing management.
Adequate amounts of all other soil nutrients need to be present to get the full benefit from phosphorus fertiliser.
Making Informed Decisions on Phosphorus Fertilisers
This publication brings together many results from the Long-term Phosphate Experiment conducted near Hamilton, Victoria. The experiment started in 1978, and has been instrumental in quantifying the production, economic and environmental effects of applying phosphorus fertiliser to pastures stocked with sheep. Its key findings include:
- Applying more phosphorus (P) fertiliser and running more stock per hectare can dramatically increase profitability.
- Pasture composition, nutritive value and pasture growth are all improved with increased fertiliser applications.
- To make a profit from applying extra fertiliser, animal production systems must utilize the additional pasture grown.
- Running more stock per hectare does not increase internal parasite or other health problems provided weights and condition scores are not allowed to drop below the normal targets for livestock.
- To maintain soil P, fertiliser needs to be applied at a rate of 10-20 kg P/ha annually, depending on the current soil test.
- At the Hamilton site (typical of the basalt plains), 80-90 per cent of the P is still in the topsoil but there has been considerable movement of sulphur (S), either off the site or deep into the soil profile.
- Sustainability indicators, such as earthworm activity and organic carbon, suggest there are no major environmental problems provided stocking rates and fertiliser input are managed to ensure that minimum pasture targets are maintained.
- At Hamilton, the amount of P required for maximum profit varies with the stocking rate. About 1 kg of P per ewe (approximately 0.8 kg P/DSE) is needed in this environment.
- On this soil type (a well-buffered clay loam), the level of P applied does not affect surface soil pH.
- Set-stocking at high stocking rates can lead to deterioration of botanical composition.
Full report: Making Informed Decisions on Phosphorus Fertilisers