Evaluation of nitrogen fertiliser in a beef production system

Abstract

This paper reports and discusses the results of 4 years of trials (1985-1988) involving 2 farmlets, one receiving 3 nitrogen applications (50 kg /ha) in autumn, winter and spring (+N) and one receiving no N fertiliser (-N). Stocking rags were 3.3 animals/ha on -N farmlet and 4.3 animals/ha on the +N farmlet for the first 3 years, with the objective being to utilise the extra N-boosted grass with extra animals/ha but not to sacrifice individual animal performance. In the fourth year the stocking rates were kept the same on each farmlet (3.3 animals/ha) in an endeavour to utilise the extra grass grown on the +N farmlet by way of increased per head performance. In 2 of the 3 years (1985 and 1987) where the +N farmlet supported the higher stocking rate, liveweight gain (LWG) did not differ between animals. In 1986 the extra animals on the -l-N farmlet had a lower LWG, whereas in 1988 the LWGs were similar for the 2 farmlets stocked at the same rate. The apparent DM responses (kg DM/kg N applied) ranged from 2 to 12. The rates of N fertiliser used in this trial do not appear to result in economic increases in pasture production for the beef production system reported here. Nitrogen fertiliser did not reduce the clover content of pastures rotationally grazed by beef cattle. Keywords beef production, nitrogen fertiliser, pasture composition, livewieght gain, economics.