Nitrogen use on Canterbury dryland pastures

Abstract

Results from the first two years of a farmlet trial carried out on a dryland Lismore soil near Ashburton, Mid Canterbury are reported. Farmlet treatments were 0, 25 (25 N) and 50 (50 N) kg N/ha applied as urea in mid-April of 1992 and 1993. Stocking rates for each farmlet were 9.5, 10.5 and 11.5 (Year l), and 11, 12 and 13/ha Borderdale ewes/ha (Year 2). For both years of the trial, there were small increases in mean pasture cover from N use despite the higher stocking rates on the N farmlets. Both mean clover content (14%) and N fixation rates (36 kg N/ha/year) were low but only declined slightly with N use. Average lamb carcass weight was lower on the 25 N and 50 N farmlet than the nil N farmlet (16.9 cf 18.3 kg). Despite this decrease, lamb carcass production per ha was significantly higher on the 50 N farmlet (216 kg/ha) compared with the nil N farmlet (199 kg/ha), Similar wool weights per ewe between farmlets resulted in an increase in wool production per ha from both N farmlets (25 N - 34.9 kg/ha, 50 N - 38 kg/ha) compared to nil N (30.8 kg/ha). Keywords: clover content, lamb production, nitrogen fertiliser, nitrogen fixation, stocking rate, wool production