The role of differential fertiliser application in sustainable management of hill pastures

Abstract

New targets for increased productivity from the sheep and beef industry are about 4% annually, at a time of ever heightening environmental awareness. A major part of this will occur by applying current technology to increase the productivity from the presently lowerthan- average farms. However leading farmers will also have to increase efficiency or productivity if they are to remain economically viable. One prospect is to examine the natural variability in hill pastures and determine if this can be more appropriately managed to improve economic returns. Hill farms have soil and topographic var iability, which can result in a wide range in pasture production. Yet a uniform rate of fertiliser is usually applied to such land. This results in under prescription of fertiliser for high yield potential zones, and similarly over prescription for low yielding zones. The conversion of easier hill land to dairying has shown how pasture productivity can be improved by applying higher rates of fertiliser and utilising the extra pasture efficiently. This approach could be applied within parts of hill farms. The main fertiliser used on hill farms is superphosphate which supplies phosphorus (P) and sulphur (S) for legume growth. This assumes that there is enough clover present to make it worthwhile. However most hill pastures, especially on steep slopes, are low in clover and as a result most are predominantly nitrogen (N) deficient for a large part of the year. The pasture responses to P and S are therefore limited by low soil N levels and N fertilisers give a better economic return. The application of a high rate of N fertiliser to hill country could more than double pasture production. The technology is almost ready to allow accurate, differential application of fertiliser to hill farms from fixed wing aircraft. This should further improve economic benefits. A differential fertiliser management plan has environmental benefits through improved soil stability and associated water quality from hill catchments. Keywords: differential fertiliser application, hill country, hill country variability