Abstract
One of the main negative anthropic effects on soil is the formation of crusts, resulting in soil degradation. This process of physical origin reduces soil water infiltration, causing increased runoff and consequently soil losses, water erosion and/or soil degradation. The study and monitoring of soil crusts is important for soil management and conservation, mainly in tropical regions where research is insufficient to explain how soil crusts are formed and how they evolve. The purpose of this study was to monitor these processes on soils with different particle size distributions. Soil crusts on a sandy/sandy loam Argissolo Vermelho-Amarelo (Typic Hapludult), sandy loam Latossolo Vermelho-Amarelo (Typic Hapludox) and a clayey Nitossolo Vermelho eutroférrico (Rhodic Kandiudalf) were monitored. The soil was sampled and data collected after 0, 3, 5 and 10 rain storms with intensities above 25 mm h-1, from December 2008 to May 2009. Soil chemical and particle size distribution analysis were performed. The changes caused by rainfall were monitored by determining the soil roughness, hydraulic conductivity and soil water retention curves and by micromorphological analysis. Reduced soil roughness and crust formation were observed for all soils during the monitored rainfall events. However, contrary to what was expected according to the literature, crust formation was not always accompanied by reductions in total porosity, hydraulic conductivity and soil water retention.
Highlights
The erosion process consists in the detachment, transport and deposition of soil particles (Pimentel et al, 1995)
The evolution of the soil surface roughness along the sequence of the 10 rainfall events can be observed in figures 1 to 6, which show the roughness evolution at time zero (T0), after 3 (T3), after 5 (T5) and after 10 rainfalls (T10)
After the 10th rainfall (T10) there was a significant reduction in roughness, forming a surface with a high smoothness degree (Figures 1 and 2)
Summary
The erosion process consists in the detachment, transport and deposition of soil particles (Pimentel et al, 1995). As in other tropical countries, the main agent responsible for soil erosion in Brazil is water (Pagliai et al, 2003). The influence of soil crusting on water infiltration was first studied by Duley (1939) and McIntyre (1958) and more recently some authors have looked into the phenomenon in tropical climate (Faria et al, 1997; Schaefer et al, 2002; Brandão et al, 2006). Brandão et al (2006) determined multiple regression equations to estimate the hydraulic resistance of crusts originated by the direct impact of raindrops as well as the rate of infiltration into crusted soils
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