Recovery of¹⁵N-labelled urea: Influence of zero tillage, and time and method of application

Abstract

The availability of N fertilizer to the crops under zero tillage versus conventional tillage may be affected by position of applied N, N immobilization and N loss from soil. The objectives of this study was to determine the influence of tillage, time of application and method of placement on the recovery of¹⁵N-labelled urea in barley (Hordeum vulgare L.) plants and in soil. Field experiments were conducted during 1984–85 at two locations (Rimbey and Ellerslie) in north-central Alberta. The lowest N recovery in barley plants occurred with surface broadcasting on zero tillage or with incorporation on conventional tillage. Placing urea in bands (23 or 46 cm lateral spacing) or nests (at poits 23 or 46 cm apart) increased the plant N recovery substantially. The plant N recovery was markedly lower with fall application than spring-applied N. For spring broadcast application, the N recovery in the plant was lower under zero tillage than conventional tillage. The¹⁵N recovery in soil (immobilized N) at harvest was greater with broadcast compared to bands or nests, and immobilized N was much greater with fall rather than spring application. The ratios of recoveries of¹⁵N in plant:soil with banding or nesting tended to be higher on zero tillage compared to conventional tillage. In all, placing urea in bands or nests increased the recovery of applied N in plants and decreased the amount of immobilized N under both zero and conventional tillage. The plant N recovery was inferior with fall application, but less so with bands or nests on zero tillage.