Effect of superficial sealing on the saturated hydraulic conductivity of the surface of a soil under "cerrado"

Abstract

Non-disturbed Red-Yellow Latosol samples collected from areas with three different management systems were submitted to five simulated rainfall periods, with an average of kinetic energy of 29 t.m.ha^-1.mm^-1, to quantify their effects on surface soil sealing, measured by the saturated hydraulic conductivity (Ko). The management systems were: traditional system of land preparation, direct drilling and undisturbed cerrado. The rainfall periods tested were: zero, 2, 5, 10 and 20 minutes. The Ko value was determined for all treatments through Darcy's equations using the constant-head method. An index "f'" is suggested, which is obtained by the ratio Ko (with the respective rainfall periods)/Ko (without rainfall). In order to describe the behavior of the "f" index for each sampled site, negative exponential equations and inverse potentials were adjusted using f values and their corresponding EC values. The results showed that the resistance of the soil aggregates to the EC and the consequent difficulty of formation of a soil surface seal are higher in an area under undisturbed "cerrado" vegetation than in cultivated areas. The hydraulic conductivity of the soil by the action of EC is established as a two-stage process, where the first stage is characterized by a sharp decrease in conductivity and the second by a slow decrease in conductivity.