Effect of ATC, N-Serve 24 E and thiourea nitrification inhibitors on yield and N uptake of barley fertilized with fall-applied N¹

Abstract

Solution urea and aqua NH₃ were injected in bands 9 cm deep and spaced 45 cm apart with and without nitrification inhibitors during October in 10 field experiments in north-central Alberta. ATC (4-amino-1,2,4-triazole hydrochloride), N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) and thiourea were used in two experiments, ATC only in another six experiments, and N-Serve 24 E only in another two experiments. Yield and apparent recovery of applied N in barley grain were determined. In the two experiments where fall treated plots were soil sampled in the following spring, 44% of the fall-applied N was recovered in the soil when inhibitors were not used. But where the inhibitors were added to the fall-applied N as NH₄−N in May was 4% and 31% without and with addition of inhibitors, respectively. Likewise, in experiments where three inhibitors were used, the treatments with inhibitors increased the yield and N recovery in grain by more than 50% compared to fall application without inhibitors. In the other experiments, fall-applied ATC or N-Serve 24 E did not always increase yield or N recovery in grain. Considering all experiments with ATC, the average recovery of applied N in barley grain was 28, 40 and 57% for fall banding, fall banding with ATC and spring application, respectively. In view of this and previous work in north-central Alberta, inhibitors injected in bands in the fall slowed nitrification and improved yield, but nests or large granules of urea were more effective.