Croplands expansion and agricultural management changes: Soil erosion scenarios in the Rolling Pampa (Argentina)

Abstract

In recent decades, the Rolling Pampa experienced land-use and agricultural management changes that promote soil erosion, such as cropland expansion into grasslands and simplified crop rotations. However, widespread adoption of no-tillage (>90 %) has been reported beneficial for soil conservation. This study estimated the impact of these changes on water erosion in the “Arroyo del Tala” watershed (≈80,600 ha) over the past three decades. Croplands expansion and rotations simplification were estimated using remote sensing classifications and NDVI trends analysis. Their impact, along with no-till adoption, was individually assessed at the watershed level by integrating the Universal Soil Loss Equation (USLE) within a GIS environment. The combined effect onerosion was then assessed by simultaneously applying the three agricultural changes. Results showed that cropland expanded into 26.1 % of the watershed between 1987 and 2015, with more than half occurring on erosionprone lands. Negative NDVI trends (2000–2017) indicated declining crop rotation intensification. Cropland expansion and rotation simplification increased estimated average soil erosion at a watershed level by 20 % and 19.8 %, respectively, leading to estimated sediment yield increases of 28.9 % and 21 % (i.e., net soil loss exported from the catchment). In contrast, no-tillage adoption reduced soil erosion by 57.2 %, decreasing sedimentyield by 58.4 %. The combined effect of all practices was a 35.3 % reduction in the estimated soil erosion and a 24.3 % decrease in sediment yield. Despite these benefits, previous studies in the same watershed showed widespread ephemeral and permanent gullies formation in recent years, suggesting that recent land-use changes primarily controlled sheet erosion while having little effect on erosive runoff. These findings support landscape planning, identifying areas vulnerable to degradation and lands suitable for sustainable cropping under diversified no-tillage systems.