Nitrogen Supply For Summer Crops Through Early Application In Ryegrass Grazed By Sheep

ABSTRACT Greater nitrogen (N) cycling is sought through Integrated Crop-Livestock Systems (ICLS). The aim of this study was to evaluate the effect of early fertilization of nitrogen applied to ryegrass grazed by sheep on the nitrogen nutrition index (NNI) of summer crops in ICLS. This study was carried out in a long-term protocol managed in the winter under two stocking methods, continuous and rotational, and two grazing intensities, moderate and low, with four replications. In summer, the area was divided into two cropping systems - soybean monoculture and a soybean/maize rotation. Fertilization was carried out in the pasture phase with 75 kg N and 60 kg P2O5 and K2O ha-1. Residual forage mass (RFM) of pasture, and phytomass yield, N content, and NNI of the summer crops were evaluated. An effect of grazing intensities was found on the maize NNI, but not on soybean. There was no effect from grazing methods. The RFM is an important source of N for the subsequent summer crop. Lower grazing intensities generate higher RFM and NNI for maize. Early fertilization did not affect soybean, because it meets part of its N demand by biological nitrogen fixation.