Rates of urea with or without urease inhibitor for topdressing wheat

The urease inhibitor NBPT(N-(n-butyl) thiophosphoric triamide) is a management alternative to increase urea efficiency in topdressing because it reduces NH3 volatilization. The objective of this study was to evaluate N recovery and yield performance of wheat (Triticum aestivum L.) 'BRS 254' fertilized with different urea or urea + NBPT rates in topdressing. The experiment was conducted from May to September 2007 in Vicosa, Minas Gerais, Brazil. Treatments followed a 5 x 2 + 1 factorial design consisting of five N fertilizer rates (30, 60, 90, 120, and 150 kg ha(-1)) as urea or urea + NBPT (Agrotain (R)) applied as topdressing and a control without N. The experiment was a randomized complete block design with four replicates. Adding NBPT to urea resulted in better N utilization by wheat plants. The 100 kg N ha(-1) topdressing rate provided the best apparent N recovery by wheat plants, whereas 90 kg ha(-1) provided the best N use efficiency.