Atributos físicos e perdas de solo, água e nutrientes sob chuva simulada em diferentes sistemas de cultivo em Planossolo

Abstract

Water erosion is one of the main degradation processes in agricultural areas, causing economic, environmental and socio-economic damage. Therefore, the aim of this study was to evaluate soil, water and nutrient losses and to carry out physical characterization of the management of floodplain areas in a Planossolo located in the south of Rio Grande do Sul. The study was conducted on experimental plots in a DBC design, with 4 treatments and 2 replications, subjected to simulated rainfall with an intensity of 60 mm h-1 over a period of 20 minutes. The treatments used were defined as T1 (fallow with spontaneous vegetation), T2 (irrigated rice in conventional preparation), T3 (direct sowing in irrigated rice monoculture) and T4 (direct sowing in crop rotation). For the physical characterization of the treatments, granulometry, soil density, particle density, total porosity, humidity and resistance to soil penetration were evaluated. After the simulated rainfall, the losses of soil, water and nutrients (P, K and Na) were assessed. The results showed that, in general, density was highest in the 0.10 to 0.20 m layer, with lower values for moisture and total porosity in this layer. PR was lowest in the top layer (0.0 to 0.10m) in treatments T2, T4 and T3, remaining below 2 Mpa and increasing from the deeper layers. With regard to soil and water losses, the highest soil losses occurred in treatments T2 and T1, 319.66 Kg ha-1 h-1 and 104.32 Kg ha-1 h-1, respectively. The highest water losses occurred in treatments T4, T1 and T3 (11.87, 11.00 and 10.52 L ha-1 h-1), respectively. The treatments with the highest losses of total nutrients, P, K and Na, were T1 and T2 (0.2787 and 0.2054 mg L-1), with the greatest presence in the soil (particulate) fraction, and the highest losses of NH4+ and NO3- occurred in treatments T2 and T3.