HERBAGE PRODUCTION AND NITROGEN RECOVERY FROM SLURRY INJECTION AND FERTILIZER NITROGEN APPLICATION

An experiment was carried out during 1986 and 1987 to examine the effects of mid‐season slurry injection and fertilizer‐nitrogen (N) application on herbage dry matter (DM) yield and N recovery. Cattle and pig slurry were injected at 56 and 112 m3 ha−1 into an established sward. Five rates of fertilizer‐N, as calcium ammonium nitrate, ranging from 0 to 120 kg ha−1 in 30‐kg increments, were superimposed on these treatments, and in both years DM yield was measured in one cut after 70 d regrowth. Slurry treatments increased herbage DM yields significantly (P < 0‐001). The efficiency of slurry total N compared with calcium ammonium nitrate‐N averaged 53% in 1986 and 86% in 1987. The mean apparent recovery of slurry total N in herbage was 55% in 1986 and 40% in 1987. Fertilizer‐N application increased (P < 0.001) the mean yields of herbage in both years but when combined with some of the slurry treatments, DM yields over the five N‐levels did not differ significantly, giving rise to interactions in 1986 (P < 0‐001) and 1987 (P < 001). It is concluded that mid‐season injection of slurry can be an effective means of utilizing slurry‐N in terms of herbage DM production and consequent N use. Copyright © 1990, Wiley Blackwell. All rights reserved