Results from an experiment on permanent grass evaluating aqueous ammonia and aqueous urea, injected in bands either 30 or 60 cm apart

Abstract

SUMMARYThe experiment was on permanent grass at Rothamsted from 1974–75. ‘Nitro-Chalk’ (ammonium nitrate-calcium carbonate mixture, 25% N) broadcast in equal amounts for each of three cuts was the standard treatment against which the following were compared: (1) prilled urea (46% N) broadcast like ‘Nitro-Chalk’, (2) aqueous ammonia (26% N) injected in winter in bands 10 cm deep and either 30 or 60 cm apart, and (3) aqueous urea (18% N) injected like the aqueous ammonia. All these fertilizers were applied to give 250 or 375 or 500 kg N/ha in 1974 and all were reapplied in 1975.In 1974 yields were larger with ‘Nitro-Chalk’ or prilled urea than with the aqueous fertilizers. Aqueous urea gave slightly larger yields than aqueous ammonia. Yields with the aqueous fertilizers were slightly larger when the injector knives were spaced 60 instead of 30 cm apart. Distribution of yield over three cuts was more uniform with ‘Nitro-Chalk’ and prilled urea (divided between cuts) than with the aqueous fertilizers. Injecting the aqueous fertilizers in bands 60 instead of 30 cm apart improved yield distribution only a little. In 1975 yields were slightly larger with the aqueous fertilizers at the first cut, but not in the drought afterwards.Relative yields over the 2 years (‘Nitro-Chalk’ = 100%) were: prilled urea, 97; aqueous urea in 60 cm bands, 96; aqueous urea in 30 cm bands, 95; aqueous ammonia in 60 cm bands, 92; aqueous ammonia in 30 cm bands, 90.In 1974 the grass recovered most N from ‘Nitro-Chalk’ and least from aqueous ammonia, but more from aqueous than from prilled urea. Recovery of N from the aqueous fertilizers was larger when injected in bands 60 instead of 30 cm apart, especially when 250 or 375 kg N/ha was given. Little rain fell in summer 1975 and recoveries of N were smaller than in 1974. The grass recovered more of the injected than the broadcast N, but no more with the injector knives 60 instead of 30 cm apart.