Interrill erosion under shrub and crop systems

Among the different forms of water erosion, interrill erosion is one of the most deleterious to the productivity of soils used in agriculture, causing losses of soil, water and nutrients. This study sought to evaluate the efficiency of environmental protection by the Shrub cover types caatinga, Guandu (Cajanus cajan) and sweet potato (Ipomoea potatoes Lam) as compared to bare soil, as well as the effect of these crops on the interrill erosion and hydraulic properties of surface runoff in a Inceptisol. For this purpose, a series of 20 simulated rainfall events in Serra Talhada - PE, Brazil, semiarid area, on the following treatments: (1) bare soil; (2) soil covered with Guandu (Cajanus cajan); (3) soil covered with sweet potato (Ipomoea potatoes Lam.); (4) soil covered with caatinga (dry forest vegetation). All runoff flow regimes were laminar and slow. The lowest rates of sediment concentration and soil detachment in the interrills were observed for caatinga and Guandu covers, the species with the highest values of soil cover, due to the higher hydraulic soil surface roughness of these crops. The sediment concentration rates in sweet potato were equal to those of bare soil, due to soil revolving to prepare the planting furrows and the rates of soil detachment were the highest of all plant covers; on the other hand, the furrows retained surface runoff. Similarly, the plant covers caatinga, Guandu and sweet potato with the respective hydraulic roughness restricting runoff resulted in exponential reductions of soil losses. The runoff coefficient in the soil covered by caatinga vegetation was the lowest (0.2) due to the greatest soil cover, roughness and absence of soil tillage.

semiarid environment; hydraulic roughness; soil cover; environmental impacts