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Argentina is a Latin American country which encounters soil degradation problems. The most productive regions have implemented conservative land practices (no-till). However, agricultural frontier has been displaced to marginal lands with arid and semiarid climates, with the consequent disappearance in many areas of native forest and land degradation. In this work, the fallout of gamma-emitting radionuclides, 137Cs and 7Be, was jointly used to assess changes in soil erosion in a recently converted semiarid ecosystem into agricultural land. 137Cs was utilized to estimate the erosion over the past 60 years, whereas 7Be was employed to estimate the erosion after the conversion of the area to cultivated land and soil tillage. For 137Cs the Proportional Model (PM), the Mass Balance Model II (MBMII) and the MODERN model were used, for 7Be the Profile Distribution Model (PDM) and the MODERN model were used. 137Cs indicates mean erosional rates of 8.2, 10.5 and 6.5 Mg ha−1 a−1, using MBMII, PM and MODERN, respectively, and that a soil layer between 0.5 and 0.8 mm was annually lost by erosion. By applying a 7Be tracer, we measured erosion rates of 2.4 and 3.3 Mg ha−1 (with PDM and Modern, respectively), indicating the loss of the upper 0.2 mm of soil. This erosion can be attributed to a few heavy rainfalls that occurred within the past 90 days. The results suggest that current land management practices have led to an increase in soil erosion. This could be attributed to the fact that the soil remains bare after crop harvest, which may compromise its conservation and future productivity. [ABSTRACT FROM AUTHOR]

Cosmogenic 7Be was used to evaluate soil loss in a mountainous micro-watershed near Belo Horizonte, Southwest Brazil. Two nearby sites were selected, a reference site in a flat area and an eroded site in a hill slope. At the reference site, soil samples were collected monthly throughout the year in order to evaluate seasonal variations of 7Be inventory in soil and its relation with the precipitation regime. Additionally, rainwater was collected and the expected 7Be soil content was predicted. At the reference site, the 7Be inventory shows seasonal variations, in accordance with the rainy season, and its distribution in the soil profile shows an exponential decrease in depth (h0 = 6.9 ± 0.6 kg m–2; r2 = 0.97). At the eroded site, two soil sampling campaigns were performed in order to measure soil erosion in the watershed. The estimated net erosion was 42.2 ± 3.7 t ha–1, indicating the loss of upper 5mm of soil per year. This corresponds to soil losses in the area in the range from moderate to severe erosion. [ABSTRACT FROM AUTHOR]

Cosmogenic 7 Be was used to evaluate soil loss in a mountainous micro-watershed near Belo Horizonte, Southwest Brazil. Two nearby sites were selected, a reference site in a flat area and an eroded site in a hill slope. At the reference site, soil samples were collected monthly throughout the year in order to evaluate seasonal variations of 7 Be inventory in soil and its relation with the precipitation regime. Additionally, rainwater was collected and the expected 7 Be soil content was predicted. At the reference site, the 7 Be inventory shows seasonal variations, in accordance with the rainy season, and its distribution in the soil profile shows an exponential decrease in depth ( h 0  = 6.9 ± 0.6 kg m -2 ; r 2  = 0.97). At the eroded site, two soil sampling campaigns were performed in order to measure soil erosion in the watershed. The estimated net erosion was 42.2 ± 3.7 t ha -1 , indicating the loss of upper 5mm of soil per year. This corresponds to soil losses in the area in the range from moderate to severe erosion.