The effects of the nitrification inhibitor dicyandiamide (DCD) on herbage nitrogen uptake when applied in late summer or early autumn

摘要

Dicyandiamide (DCD) has been shown to reduce nitrate leaching by slowing the conversion of ammonium to nitrate in the soil, thereby increasing the quantity of available nitrogen (N) in the soil for uptake by herbage. The objective of this experiment was to observe the effects of DCD on annual herbage N uptake when applied to the growing sward in late summer and early autumn. The experiment was a block design with three replicates of each treatment at two sites. The sites were: (1) a free-draining acid brown earth of sandy loam to loam in texture at Moorepark (MPK), and (2) a fine loam soil with imperfect drainage at Johnstown Castle (JC). The factors examined in the experiment were as follows: urine application, DCD rate and time of DCD application.Annual herbage N uptake increased significantly in both measurement years at MPK when urine was applied (P < 0.01). There was a significant effect (P < 0.01) of urine application date on annual herbage N uptake at both sites. There was no significant effect of DCD rate or application date on annual herbage N uptake at either site.