Escoamento superficial e erosão entressulcos em planossolo sob pastagem com diferentes períodos de implantação

Abstract

Soil is one of the most basic and important natural resources, being the basis for the development of livestock, which is important in the national scenario, and that depends a lot on the cultivation of pastures for animal feed. However, pasture cultivation in Brazil is often treated as a minor activity, which results in pasture and soil degradation. Of the factors for degradation, and soil erosion is a major, causing loss of soil particles, nutrients and organic matter. Thus, in view of the importance of pasture cultivation and soil erosion, the objective of this work was to evaluate the disintegration rates in mulch and hydraulic variables of runoff under simulated rainfall in Planosolo under pasture with different periods of implantation. To carry out this study, three pasture areas with two-year (P2), three-year (P3) and four-year (P4) periods and a comparative area with native vegetation (VN) were selected over a haplic planossol, located in the municipality of Duas Estradas-PB. Deformed soil samples were collected from the 0-20cm layer and undeformed from the 0-10cm and 10-20cm layers, used for erosion tests and for soil physical and chemical characterization, respectively. The simulated rain tests were carried out in experimental plots filled with a soil layer in a greenhouse, and a slope of 0.05 m m-1, for the application of rainfall, using a sprinkler nozzle located at 3.1 m. above the plots, simulating precipitation of 130 mm h-1, lasting 75 minutes. Surface runoff hydraulic variables, soil disintegration rate (Di), intercrop erodibility (Ki) and total soil losses (PSi) were evaluated. According to the results obtained, the flow regime in the tests was the slow laminar, confirming the occurrence of cross-erosion, the disintegration rates (Di) and erodibility (Ki) did not vary between the evaluated conditions, indicating that the conversion of the Native pasture vegetation did not significantly affect soil susceptibility to erosion. Regarding soil loss rates (PSi), there were differences between treatments P3 and VN, but not between these treatments and P2 and P4, indicating that the highest losses do not result from direct pasture influence, but from another soil attribute. Finally, the conversion of native vegetation to pasture did not change soil erodibility, however, increased soil losses.