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Phosphorus-efficient legume pasture systems
Phosphorus (P) fertiliser is a critical input for productive pasture systems in southern Australia but the cost of fertiliser has risen substantially. There is a major opportunity to counter rising costs by improving the efficiency of P-use on farms. This project determined the critical soil test P requirements (i.e. soil test levels needed for near maximum growth) of alternative pasture legumes to establish soil fertility benchmarks for pasture management. Two species of serradella (Ornithopus sativa, O. compressus) were found to have very low critical P requirements relative to subterranean clover (Trifolium subterraneum) and it was estimated that their use in fertilised pastures could reduce P fertiliser costs by ~30% annually. When grown in moderately P-deficient soils the serradellas also achieved about twice the yield of subterranean clover. Low-P pasture systems can be developed immediately in areas where serradellas are already grown. Wider adoption hinges on understanding how widely serradellas can be grown in permanent pasture areas. High P efficiency was associated with long, fine roots that have long root hairs. This allows a plant to forage effectively for nutrients in soil. This knowledge is being used to identify more P-efficient lines of subterranean clover to improve yields in moderately fertilised paddocks and to push subterranean clover closer to the very high P efficiency of the serradella species.
This page was last updated on 28/12/2017
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