RESPONSE TO NITROGEN FERTILISER APPLIED TO DAIRY PASTURES IN AUTUMN AND SPRING IN TARANAKI

Abstract

Nitrogen response trials conducted in Taranaki on dairy pastures over a 10 year period are summarised. At both high and low altitudes responses were variable in winter but very consistent in spring(September and October) with the higher altitude pastures being more responsive. Nitrogen applied in autumn(early April) at low altitudes gave consistent responses over a three year period at one site despite markedly different summer climatic conditions between years. Further investigations at a range of altitudes and climates throughout Taranaki indicated extreme variability, and the only consistent and worthwhile responses ( > I I kg DM/ kg N) were obtained at the lower altitude sites. The efficiency of response to nitrogen (kg DM/ kg N) applied in autumn and winter declined little with increasing rates from 25 to 100 kg N/ ha and responses to higher rates occurred over a longer period. The occurrence of grass grub affected the relative responsiveness of pastures to nitrogen but the yield increments to nitrogen were similar on pastures of low and high grass grub numbers.