THE EFFECT OF FERTILIZER NITROGEN INPUT ON THE STOCK-CARRYING CAPACITY OF RYEGRASS WHITE CLOVER SWARDS CONTINUOUSLY GRAZED BY BEEF-CATTLE

An experiment was carried out over 5 years to examine, under a continu ous grazing management system, the beef producing capacity of ryegrass (cv. Talbot)/white clover (cv. New Zealand Huia) swards receiving 60 or 360 kg of fertiliser N per hectare. There were two stocking rates a t each N level with two replicates per treatment and six animals per r eplicate. Initial stocking rates in the first 2 years of the experimen t were 7.2 and 9.0 animals/ha for the low-N swards and 10.8 and 13.5 a nimals/ha for the high-N swards. These stocking rates were reduced by 33% in June by extending the grazing areas to include silage aftermath s. In the subsequent years, initial stocking rates on the low-N swards were increased to 9.6 and 12.0 animals/ha and these were reduced by 5 0% in June. Mean clover proportions over the second to fifth grazing s easons for the low-N grazed swards and silage aftermaths were 78 and 1 65 g/kg dry matter, respectively. Although the proportions of clover i n these swards were low, it was evenly distributed and the proportion of clover in the herbage consumed was estimated to be more than double that in the herbage mass. The stock-carrying capacity of the low-N sw ards was 74% in the first year, and 86% in subsequent years, that of t he high-N swards.