Intensidade de pastejo e adubação nitrogenada sobre a qualidade física do solo em sistema de integração lavoura-pecuária

Abstract

In recent years, the crop-livestock integration has been widely used in Brazil because of the numerous benefits that can be achieved with the adoption of this system. However, there are still doubts about its impacts on land degradation due to excessive trampling of animals. So the aim of this work was to evaluate the possible impacts of cattle trampling on the physical quality of the soil under diferetes levels of nitrogen abudação and grazing intensities. the experiment was conducted in a rural property located in the municipality of Abelardo Luz – SC was selected, with a dystrophic Oxisol soil, where 12 paddocks were built as the experimental units. The treatments consisted of two factors, the first was grazing intensity, characterized by two grazing sward heights, for the sorghum two measures were used, 30 and 60 cm for grasslands and 15 to 30 cm for oats (low and high grazing intensity, respectively). The second factor consisted of two levels of nitrogen topdressing (low and high, 100 and 300 kg N ha-1, respectively). Each of them had three replications.The sampling for assessment of soil physical quality was performed after each grazing and harvesting the grain. Samples were collected at three randomly selected points in each experimental unit, with the use of 3 cm and 6 cm diameter rings. These samples were collected at layers of 0-5 cm, 5-10cm, 10-15cm and 15-20 cm. The values of soil density were not statistically different during the treatments, and the soil density became a less sensitive indicator for checking the loss of soil physical quality, however, an increased density at depth was observed. No statistically significant differences were found for the macroporosity. The microporosity values and total porosity statistical differences after grazing in oats, showing higher values at low grazing intensity with the application of nitrogen and high intensity without nitrogen grazing. The physical attributes after the corn harvest did not differ statistically, being suitable for the development of culture.