Animal supplementation and forage legume in an integrated crop-livestock systems: nitrogen export by animals, cycling, and soybean productivity

Abstract Animal supplementation and grass-legume mixture can increase the stocking rate and crop and animal waste in the soil. Our hypothesis is that these alternatives can increase the amount of nitrogen recycled in an integrated crop-livestock system. We analyzed in an integrated crop­livestock system, whether the nitrogen recycling and the soybean crops are influenced by legume and animal supplementation (1% live weight) in beef cattle production. We evaluated animal nitrogen intake, the recycled through feces and urine, and the amount of nitrogen retained in beef cattle carcass. In summer, the rate of dry matter, and nutrient release from the residual biomass after grazing and feces of animals, the export of nitrogen by soybean crops, and grain production. It was possible to increase the stocking rate in 21% through supplementation and with this there was a 33% increase in the return of nitrogen through feces and urine compared to the control. This result interfered with the export of nitrogen in grains, which was 9% higher in paddocks where there was animal supplementation. The amount of nitrogen exporting by the animals, in 90 days of grazing, did not differ between treatments, averaging 8.18 kg ha − 1 of N. Nitrogen return in a complete cycle increased by 19%, where animal and legume supplementation was used. We concluded that the supplementation and use of legumes are alternatives to increase the nitrogen recycled in integrated farming systems. Of the total N exporting, about 3 to 4% are through animals, and 96 to 97% are through soybean grains.