Nitrogen fertilization as a weed management tool in an integrated crop-livestock system

Abstract

The objective of this work was to evaluate the effect of nitrogen fertilization rates applied to winter forage crops on weed occurrence and bean crop yield in the summer. The experiment, carried out in the 2016/2017 season, is part of a long-term protocol under an integrated crop-livestock system. The applied nitrogen fertilization rates were 0, 75, 150, and 225 kg ha^-1 N. The residual mass of the forage crops (ryegrass and black oat) was quantified before the summer crop (common bean) was planted. The seed bank was collected from 0 to 5.0 cm soil depth in October 2016, and the emerged plants were quantified at 15, 30, 45, and 60 days after bean emergence. The amount of residual biomass was 60% higher with the application of 225 kg ha^-1 N than without nitrogen fertilization, resulting in a 65% reduction in emerged weeds and an almost threefold smaller seed bank. A reduction in weed infestation was observed up to 30 days after bean emergence. Integrated weed management should consider nitrogen fertilization of winter forage crops as a tool to reduce weed infestation in crop-livestock integration.