Soil cover assessment in slopes of a soil after subsurface strata extraction

Abstract

The run-off and sediment yield were measured in steeply slopes covered with inert protection or vegetal species in two slopes gradients. The study was carried out in Maipú (Santiago) after the subsoil extraction of Rinconada de Lo Vial series (Typic Xerochrepts), a sandy loam soil from Central Chile. Covers of sea fig (Carpobrotus sp.) (T1), maize stubble (T2) and coarse gravel (T3) were evaluated using a control with spontaneous vegetation (T0). The treatments were established in two slope gradients (1:2.25 and 1:1.00, respectively) with three replicates. Precipitations were simulated by sprinkle irrigation, with rainfall intensities between 1.43 and 1.87 mm h-1, evaluating the run-off (%) and the mass of eroded sediments.
The control (T0) showed the higher run-off, reaching values of 30 and 50% of total rain in slopes 1:2.25 and 1:1.00 respectively, the run-off of the remaining treatments were significantly lower and without differences among them. The sediment yield is not significant, reaching 10 and 26 kg ha-1 (slopes 1:2.25 and 1:1.00) in the control and less than a half for the remaining treatments. Although the use of organic residues assures a high cover, the maize stubble (T2) did not present the best results in run-off and sediment yield, with sea fig (T1) and gravel (T3) being the most recommended for slope protection. In the studied site, precipitations greater than 1.65 and 1.80 mm h-1 produced an increase of the evaluated parameters in the 1:2.25 and 1:1.00 slopes, respectively.