Selection of a legume to use in a low phosphorus loss pasture

Abstract

© 2016 The Royal Society of New Zealand. Phosphorus loss from pastures can impair surface water quality. Losses can be partly minimised by maintaining a low soil Olsen P concentration, but there is still potential to reduce these further by minimising P lost from plant shoot material. Furthermore, although ryegrass can produce well at low Olsen P, many legumes cannot. We tested and categorised the potential for P losses (as water extractable P) from shoot material for 10 species (ryegrass, legumes and herbs) and the supporting Pallic soil over a range of Olsen P concentrations. White clover was categorised as having low potential for P loss from shoot material while exhibiting high yield relative to other species. This was especially the case at an Olsen P concentration of 15 mg kg-1 - targeted as the minimum Olsen P required for good ryegrass yield, but requiring little P inputs, and likely to lose little P to surface water. However, other legumes may be more suitable under different soil or climatic conditions.