Rates of urea with or without urease inhibitor for topdressing wheat.

Marcelo Curitiba Espindula1, Valterley Soares Rocha2, Moacil Alves de Souza2, Marcela Campanharo3, and Guilherme de Sousa Paula2
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 Viçosa, Minas Gerais, Brazil. Treatments followed a 5 × 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®) 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.
Keywords: Triticum aestivum, nitrogen fertilization, NH3 volatilization, NBPT, N-(n-butyl) thiophosphoric triamide.
1Empresa Brasileira de Pesquisa Agropecuária, Embrapa Rondônia, BR 364, km 5.5, 76.815-800, Porto Velho, Rondônia, Brasil. *Corresponding author (marcelo.espindula@embrapa.br).
2Universidade Federal de Viçosa, Departamento de Fitotecnia, Av. P.H. Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. Faculdades Integradas Aparício Carvalho, Rua Araras 241, Jardim Eldorado, 78912-640, Porto Velho, Rondônia, Brasil.