Soil physical attributes in an integrated crop-livestock system with pasture managed under different sward canopy heights and different timings of nitrogen application

Abstract

This study aimed to evaluate the physical attributes of soil in an integrated crop-livestock system with winter pastures managed under different N fertilization timings and canopy heights after winter and the soybean crop. The experimental design used was randomized blocks with the treatments in a 2 × 2 factorial arrangement (two canopy heights and two N application timings), with three area replications. The canopy heights were 11 and 24 cm kept by continuous stocking grazing method since May to November (175 days). Fertilization timings as N-pasture fertilization and N-corn fertilization (phase before the winter pasture). Treatments characterized as N fertilization inversion were applied with fertilization timings as N-pasture fertilization and N-corn fertilization (phase before the winter pasture). Soil density, total porosity, and moisture content were evaluated after winter pasture (black oat + annual ryegrass) and after the subsequent summer soybean crop. The sampling spots were georeferenced and analyzed using geostatistics, considering the position in the slope of landscape. Soil physical attributes were not influenced by canopy height nor N fertilization timing (P>0.05). Soil density was reduced by 13.3% (from 1.11 to 0.98 g cm-3), whereas total porosity (from 0.58 to 0.62%) and moisture content (from 32.73 to 35.73%) increased by 6.9% and 9.2% after the soybean crop in relation to the values obtained in the winter pasture. The higher elevation areas had higher moisture content, total porosity, and lower density than the lower elevation areas, regardless of the time of evaluation. Well-drained soils were more resistant to compaction by animal trampling than moderately drained soils. In well-managed integrated crop-livestock systems in humid subtropical climate regions, the surface compaction of clayey soils in winter pastures is light, non-limiting, and disappears after the subsequent summer crop.