Fate of ¹⁵N Urea Applied to Wheat Grown under Upland Irrigated Condition on a Typic Ustochrept

The fate of ¹⁵N urea applied to a Typic Ustochrept for growing wheat under upland, irrigated, confined field microplot condition was investigated by constructing a ¹⁵N budget comprising fertilizer N recoveries from soil-plant system and quantification of N losses. There was significant response of wheat yield to increasing rate of N application and yield efficiency varied from 18.8 to 22.2 kg grain per kg N. For two rates of N application, fertilizer N recovered by grain plus straw of wheat ranged from 28.0 to 45.1 kg N ha⁻¹ and 1 N recovered from the soil ranged from 14.1 to 32.2 kg N ha⁻¹. Ammonia volatilization was the main cause for N loss and varied from 5 to 12 kg N ha^−l for the two rates of N application. Leaching loss of N was not significant. Unaccounted for fertilizer N, as determined by the difference from mass balance studies, ranged from 2.9 to 10.7 kg N ha⁻¹.