Quantifying the impact of no-tillage on soil redistribution in a cultivated catchment of Southern Brazil (1964–2016) with $^{137}$Cs inventory measurements
Résumé
No-tillage is a soil management practice that results in reduced soil losses when compared to conventional tillage systems. However, when this practice is overly simplified, it may lead, over the years, to higher levels of soil loss than expected. In this context, this study sought to compare the rates of long-term soil redistribution on three hillslopes used for grain production under different soil management on deep weathered soils (Ferralsols) in southern Brazil. Soil samples were collected along three transects in different hillslopes characterized by either no-tillage or conventional tillage. Cs-137 inventories were used to estimate the soil redistribution rates based on Mass Balance Model - 2. The results indicate that along the three slopes and during the last five decades, changes in soil management impacted the patterns of soil erosion in the landscape, showing the occurrence of significant soil loss in the upper and backslope segments, and deposition in the lower parts of the three hillslopes studied. Even with no-tillage, erosion has continued to occur, although at lower rates when compared to conventional tillage. The use of the $^{137}$Cs marker associated with the Mass Balance Model - 2 (MBM - 2) conversion model provided an effective tool for estimating soil redistribution rates under different management systems. Although the introduction of no-tillage in the last 28 years has reduced erosion rates, these processes remain significant and the implementation of additional runoff and/or erosion control practices is recommended in order to keep erosion rates at sustainable levels.
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