Soybean growth and nitrogen accumulation by soybeans in response to desiccation times of Urochloa brizantha pasture and nitrogen fertilization

Abstract

The desiccation time of high-biomass pasture and nitrogen (N) fertilization of pasture and soybean can influence the soybean sowing, establishment and growth. The objective of this study was to evaluate how the time of desiccation of the preceding pasture of Urochloa brizantha cv. BRS Piatã, cultivated at three levels of N, and by the soybean N fertilization affect soybean growth and N accumulation. Three N rates (0; 150 and 300 kg ha-1), broadcast as urea on the U. brizantha pasture were evaluated separately in each N level, every one considered as one experiment. In each experiment, five times of pasture desiccation were evaluated (60; 45; 30; 15, and 1 day before soybean sowing) and two levels of soybean N fertilization: 30 kg ha-1 (urea) broadcast at sowing or without N fertilization. A randomized complete block design with five replications was used. Early desiccation of U. brizantha pasture favors the establishment of soybean and promotes an increase in biomass and N accumulation in the vegetative stages, however these differences are not observed during the grain filling, regardless the soybean N fertilization. The soybean yield was not influenced by the desiccation time. N fertilization with 30 kg ha-1 at sowing intensifies soybean growth at the vegetative phase, but after full flowering, there were no effects on biomass and grain yield, independently of the desiccation time.