Appraising soil physical degradation using the Visual Evaluation of Soil Structure (VESS) in the Western Highlands, Cameroon

Identifying key soil physical indicators is crucial for strengthening efforts to conserve fragile ecosystems and ensure food security. This study investigates the effects of land use, topographic position, and soil texture on the variation of physical soil indicators in the highland of Cameroon. The Visual Evaluation of Soil Structure (VESS) was the primary proxy for assessing structural soil quality. A stratified nested random sampling design was used to sample soils across land use types, specifically the forest (FS), Agroforestry systems (AGF), natural fallow (FLW), Eucalyptus fields (ECP), Crop fields (CRL), and Grazing land (GRL). We found that many soil's physical indicators differed based on land use and textural classes, as did the soil structure, with FS and AGF showing the best values, whilst GRL, CRL, and ECP exhibited the lowest. A deviation of about 50 % emerged between the FS reference and many other land uses for many soil indicators, witnessing a high soil structural swing in the landscape. However, the topographic position did not show a significant variability (p > 0.05) of any soil physical indicators, implying that soil variability is mainly anthropogenic. The soil physical quality index (SQI) sequence for land use is FS > AGF > CRL > FLW > ECP > GRL, with the highest value (0.56) in FS and the lowest in GRL (0.34). The SQI and VESS Scores are strongly and negatively related. The VESS method can serve as a valuable tool for quickly assessing physical land degradation conditions, monitoring soil degradation, and providing decision support in highland agroecosystems.