Three grazing intensities on nitrogen soil recycling

A three-year experiment was carried out in a commercial dairy unit, in a red ferrallitic soil sown with star grass (Cynodon nlemfuensis). Grazing intensities were randomly established: 150, 300 or 450 AU/ha/day, to study the effect of nitrogen recycling in relation to grazing in tensity and its effect on cattle dung deposition in the paddocks, the percentage of area physically covered, as well as the total amount of N deposited. The amount of cattle dung patches in the paddocks, as well as the percentage of the grassland area they covered and the nitrogen deposited, were favoured (P < 0.001) when grazing intensity increased from 150 to 450 AU/ha/day, with coefficients of determination of 0.96, 0.96 and 0.98, respectively. The analysis of soil nitrogen balance shows that. as the grazing intensity increases, losses decrease (-67.81, -33.02, -1.13 kg nitrogen/ha/year), while for plant components, the positive balance decreases and the losses increase in the animal component (101.18, 69.62, 35.38 and 85.85, -146.54, -205.28 kg nitrogen/ha/year per plant and animal, respectively). The study shows that oil increasing grazing intensity, cattle dung amd nitrogen depositions on the soil are greater, but they do not cover the extractions. Therefore increasing grazing in tensity also increases the nitrogen losses in the soil-plant-animal system.