Determination of Net Soil Erosion Rate Using 137Cs in a Slope Agroecosystem

Resumo

The severe and moderate erosion of soils has caused the degradation of 80% of the agricultural land of the planet. Sloping agriculture, without soil conservation measures, together with the occurrence of extreme climatic events, increasingly frequent, as a consequence of climate change, has accelerated these phenomena, at rates of 5-7 million degraded hectares/year. In this work, 137Cs, an anthropogenic environmental radionuclide, was used to estimate soil erosion rates in a vegetable agroecosystem located in Waraira Repano National Park, Vargas State, Venezuela. With this aim, three soil cores were extracted, sectioned at depths of 0-20; 20-40 and 40-60 cm, in each of the 26 and 28 equidistant vertices distributed in the study and reference sites, respectively. Measuring the activity of 137Cs in each depth, it was possible to establish the contrasting patterns of its distribution within the profiles; and through the use of conversion, Proportional and Mass Balance I models, the estimation of erosion rates was obtained. These showed gross and net erosion rates of 24.7 and 39.7; and 19.8 and 29.3, Mg ha-1 year-1, respectively. The benefits of nuclear techniques in soil erosion and redistribution studies are confirmed; allowing forecasting prospectively and retrospectively, the vulnerability of the productive capacity of the soils, which compromises the sustainability of agriculture, particularly in soils that are very susceptible to erosion, when their degree of water saturation is exceeded.