DOSES, FONTES E ÉPOCAS DE APLICAÇÃO DE NITROGÊNIO E M ARROZ DE TERRAS ALTAS CULTIVADO EM SISTEMA DE SEMEADURA DIRETA

Abstract

The crop demand by nitrogen varies from one crop to other as well as the amount and applica- tion time, and this nutrient can be lost by leachin g, volatilization and erosion. The objective of thi s study was to evaluate doses, sources and times of nitrogen appli cation in rice of high lands cropped in no till sys tem. The work was conducted in Selvíria, State of Mato Gross o do Sul, Brazil, in a soil originally under Cerrad o vegeta- tion. A randomized blocks design, with the treatmen ts disposed in a factorial scheme 5x3x2 was used. T he treatments were constituted by five nitrogen doses (0, 50, 100, 150 and 200 kg ha -1 ), three nitrogen sources (urea; ammonium sulfonitrate plus nitrification inh itor and ammonium sulfate) and two application time s (at sowing or at flower bud differentiation), with four repetitions. The sources of nitrogen, as well as t he applica- tion times had similar effects for most of evaluati ons. The N doses influenced linearly or with quadra tic adjust- ment the plant height, N leaf content and grains yi eld, in the two growing seasons. The chlorophyll co ntent and the number of ears m -2 were affected only, in the first year. The highest yield in the growing season of 2007/08 was obtained with the dose of 149 kg ha -1 of N. In 2008/09 growing season the increase of N doses provided increment in the grains rice yield, until the maxim um dose evaluated (200 kg ha -1 of N).