NDVI from Sentinel-2 images: a soil erosion indicator in Mediterranean rainfed croplands

Abstract Background and aims Soil erosion in Mediterranean rainfed agriculture—primarily caused by tillage and prolonged bare soil exposure—leads to horizon loss and sediment accumulation, severely affecting productivity. This study demonstrates that the NDVI of herbaceous crops can be statistically linked to erosion/deposition processes, conceptualized here as three “truncation–accretion phases”: i) truncation of the A horizon, ii) truncation of A + B horizons, and iii) accretion of A horizons through sediment deposition. Method Research was conducted in a Central Spain site with Mediterranean climate and evolved Alfisols (A/Bt/C profile). Sentinel-2 imagery from five dates between 2017 and 2021—years with contrasting weather—was used to relate NDVI dynamics to these phases. Climatic variability in rainfall and temperature was also analyzed. Results Accretionary soils had the highest NDVI values, intermediate values were associated with A horizon loss, and the lowest with A + B horizon loss. These patterns were consistent with observed pedological differences and meteorological conditions during the crop cycle. A Random Forest model trained on multi-temporal NDVI data achieved strong performance (73.3% overall accuracy, Cohen’s Kappa = 0.60), particularly for extreme phases, with reduced accuracy for transitional soils. Conclusion NDVI effectively captures the functional status of subsurface horizons, offering indirect insight into soil degradation processes not easily detectable by spectroscopic methods.