Soil Fertility in Crop-Livestock System Subjected to Nitrogen Fertilization and Grazing

The aim of this study was to evaluate the effects of sheep grazing and increasing rates of nitrogen fertilization on oats + ryegrass at winter on the soil K, Ca, H + Al, Mg and P concentrations in a crop-livestock system with beans and corn crop succession during summer after four years (2006-2009) of the experiment establishment. Treatments consisted of different nitrogen levels (0, 75, 150 and 225 kg ha-1) with and without sheep grazing Lolium multiflorum Lam and Avena spp. Soil chemical traits were evaluated at depths of 0-5, 5-10, and 10-15 cm. The experiment was laid out as random block design in a split-plot scheme with three replications. Soil K content were higher at the superficial soil layer and at the treatment with 150 kg ha-1 N and remained high along the four years of assessment. Animal grazing at winter results in better soil chemical traits in relation to the soil Ca and H + Al. There were no nutrient (K, Ca, P and Mg) losses or extraction when under overgrazing, a fact that confirms the possibility of using animals in the crop-livestock areas without affecting its chemical traits. There was also an increase in Ca and SB concentrations with grazing, including in subsurface soil.