The profitability of nitrogen fertiliser applications on seasonal supply dairy farms : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Farm Management at Massey University

Abstract

Grassland farming in New Zealand is characterised by an almost complete reliance on pasture herbage as the diet for livestock throughout the year. Nitrogen (N) for grass growth is obtained from legumes, particularly white clover. The success of this grass-clover association can be largely attributed to the very high levels of N fixation possible under New Zealand climatic conditions 1√. The supply of available N in the system is not regular, however, and periods of temporary N deficiency occur annually in mixed pasture. Consequently, the question arises as to whether the productivity of the grass-clover pastures can be profitably raised by the use of fertiliser N. If the use of fertiliser N is to be economic, it must either allow a new farming system to become feasible and profitable, or improve the profitability of an existing system. Advocates of increased N fertiliser use in New Zealand are not in agreement as to which alternative shows the greatest potential. Mitchell (1969) anticipates a considerable decline in future fertiliser N costs and suggests that it could be used to substitute entirely for clover N. Animals are yarded throughout the year and are fed by high yielding summer and winter adapted crops, which are liberally dressed with fertiliser N, cut, and stored in silos 2√.[FROM INTRODUCTION]