White clover or nitrogen fertiliser for dairying?

Abstract

Annual production in New Zealand dairy pastures is limited by nitrogen supply and therefore requires nitrogen fertiliser to increase annual pasture production. This paper summarises the advantages and disadvantages of clover nitrogen and fertiliser nitrogen including the effects of both nitrogen sources on feed quantity and quality, factors limiting nitrogen fixation and nitrogen fertiliser response, defoliation effects on white clover (Trifolium repens L.), animal health problems associated with clover and nitrogen fertiliser, and environmental effects. UDDER, a dairy farm simulation model, is used to predict the nitrogen fertiliser rate and white clover content in pasture necessary for optimum pasture production and feed quality. Maximum gross margins per ha and a high level of milksolids production per ha and per cow can be best achieved by combining nitrogen inputs from white clover and nitrogen fertiliser. The model predicts best results would be achieved with clover contents of 30-40% and nitrogen fertiliser rates of 100-200kgN/ha/yr. Keywords: dairying, feed quality, nitrogen fertiliser, nitrogen fixation, Trifolium repens