Determined runoff and calculated infiltration of water into the soil under doses of pig slurry on a plot scale

Pig slurry (PS) increases water infiltration into the soil and reduces runoff, which characterized the objective of this research in the Ultisol and Cambisol soils in southern Brazil. Runoff was determined in the field in four simulated rainfall events during the soybean (Glycine max) cycle, and infiltration was calculated by the difference between rainfall and runoff. There was no effect of the PS dose on runoff and soil water infiltration, but these variables underwent some numerical changes, possibly due to other factors. In the Ultisol, there was a rapid increase in the runoff rate due to low soil cover, with a rapid decrease in infiltration in the first rainfall, whose effect diminished in the second rainfall because at that time there was greater soil cover by the aerial part of the soybean. In the third and fourth rainfals, the soil was completely covered by soybeans, soil moisture was very low, which increased infiltration and delayed the onset of runoff. In the Cambisol, the mass of crop residues was high throughout the research period, protecting the soil surface from the energy of rainfall, which resulted in a slow increase in runoff. In both soils, there was an increase in porosity throughout the soybean cycle, with a possible increase in saturated hydraulic conductivity and water infiltration into the soil, attributed, in part, to the rooting effect of soybeans.