Fate of 15N-urea applied to wheat-soybean succession crop

Bragantia

Antonio Enedi Boaretto²  Eduardo Scarpari Spolidorio¹  José Guilherme De Freitas¹  Paulo Cesar Ocheuze Trivelin²  Takashi Muraoka²  Heitor Cantarella¹ 

[1] ,USP Centro de Energia Nuclear na Agricultura Piracicaba SP

关键词: Nitrogen fertilization;    efficiency;    ammonia;    volatilization;    adubação nitrogenada;    eficiência;    amônia;    volatilização;   

DOI  :  10.1590/S0006-87052004000200011

来源: SciELO

【 摘 要 】

The wheat crop in São Paulo State, Brazil, is fertilized with N, P and K. The rate of applied N (0 to 120 kg.ha-1) depends on the previous grown crop and the irrigation possibility. The response of wheat to rates and time of N application and the fate of N applied to irrigated wheat were studied during two years. Residual N recovery by soybean grown after the wheat was also studied. The maximum grain productivity was obtained with 92 kg.ha-1 of N. The efficiency of 15N-urea utilization ranged from 52% to 85%. The main loss of applied 15N, 5% to 12% occurred as ammonia volatilized from urea applied on soil surface. The N loss by leaching even at the N rate of 135 kg.ha-1, was less than 1% of applied 15N, due to the low amount of rainfall during the wheat grown season and a controlled amount of irrigated water, that were sufficient to moisten only the wheat root zone. The residual 15N after wheat harvest represents around 40% of N applied as urea: 20% in soil, 3% in wheat root system and 16% in the wheat straw. Soybean recovered less than 2% of the 15N applied to wheat at sowing or at tillering stage.

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