Preliminary experimental data on surface runoff and soil loss in the Caatinga

Semi-arid regions are naturally sensitive to soil erosion due to sparse vegetation cover and concentrated rainfall regime. Absence of conservative practices increases soil loss and reduces water retention. Despite the propagation of erosive process in the Brazilian semi-arid region, few studies address the spatial and temporal distribution of surface erosive processes. Therefore, the present study presents preliminary results of a monitored soil loss and runoff experiment in the Brazilian semi-arid region. Four plots were set up on the dominant soil groups, Luvisols and Regosols, traditional land uses, fallow system and cactus palm cultivation. Precipitation, surface runoff and soil loss were monitored for 22 months. The plots with the fallow system were more efficient in containing the hydro-erosive dynamics than the plots with the cactus palm. The high difference in soil erosion between fallow system plots and cactus palm indicates that the human impact on soil loss is substantial. The significant correlation between precipitation and surface runoff allows the prediction of surface runoff. The weak correlation between precipitation and soil loss indicates that erosion is complex, with a strong influence on soil properties and use. The propagation of erosive processes in the Brazilian semi-arid region induces loss of soil fertility, acceleration of the desertification process and impoverishment of rural communities. Specific conservative practices should be developed to reduce soil loss and mitigate anthropic disturbance in these areas. The surface runoff in Luvisol was up to 47% higher than those measured in Regosol. The plots with cactus palm showed a loss of organic carbon and nitrogen up to seven times greater than the plots in fallow system. Regosol is more sensitive to land-use change compared with Luvisol.