Water, Soil and Nutrients Losses by Runoff at Hillslope Scale in Agricultural and Pasture Production in Southern Brazil

Agricultural activity, if not well managed, is an important source of water pollution mainly by surface runoff. The aim of this study was to evaluate losses of water, soil and soluble nutrient (phosphorus, nitrogen and carbon) via runoff in large plots (hillslope from 3,000 to 11,000 m2) at slope of 4 to 5% in annual crops (corn and sunflower) and pasture systems under no-tillage and no-pesticides. The study was carried out at the Canguiri Experimental Farm of the Federal University of Paraná, Southern Brazil, in soil classified as Ferralsol in three systems (crop, pasture and crop-pasture). Soil physical and chemical attributes as well as topographic indices and soil cover were investigated to evaluate the possible impacts of these variables on losses. The runoff was measured after each rainfall event from November 2014 to October 2015. Runoff samples were taken to analyse sediment and nutrients. All systems had low water, soil and nutrients losses compared to no conservative agricultural systems. Higher losses occurred in the annual crops system and were influenced by soil cover, with an annual runoff coefficient of 0.62% (7 mm of water loss) and an annual soil loss of 2.6 kg ha-1. The seasonality (winter/summer) did not influence soil, water and nutrient losses.