Factors contributing to soil crusting and its relationship with soil aggregate stability in agricultural lands in southern Mali, west african region

Abstract

This dissertation focused on studying soil crusting in agricultural soils in Southern Mali, as part of an international cooperation project titled "Preservation of Productive Potential in Cotton-Producing Areas in Mali - Cotton Soils", involving the Federal University of Lavras (UFLA). Soil crusting and sealing pose significant challenges in agricultural regions, especially in Sub-Saharan Africa where small-scale farming is prevalent. Soil crusting entails the development of thin, rigid, impermeable layers on the soil surface, leading to reduced water infiltration, increased runoff and erosion, and decreased germination, seedling emergence, and productivity. Various factors such as rainfall intensity, topography, soil attributes, and inadequate soil management influence this process. To understand the factors affecting soil crusting and aggregate stability in Southern Mali, this study aimed to (1) investigate the impact of specific soil attributes (physical, chemical, mineralogical) on soil crust formation, and (2) evaluate soil aggregate stability under agricultural and native vegetation, and assess the relationships between different structural stability indices, soil attributes, and soil crusting susceptibility. Soils from agricultural and native areas in the Sikasso district of Southern Mali were sampled from the top 10 cm and analyzed for various physical, chemical, mineralogical, and micromorphological attributes. Soil aggregate stability was assessed using three methodologies: wet sieving, the High Energy Moisture Characteristic (HEMC) method, and Clay Dispersion. The studied soils exhibited high silt and fine sand contents, and low organic matter leading to significant crusting formation. They displayed a high risk of aggregate disruption and moderate susceptibility to soil crusting. Native vegetation areas showed higher structural stability indices and lower crusting susceptibility compared to agricultural sites. Additionally, a significant negative linear relationship was found between crusting susceptibility and aggregate structural stability indices. To enhance soil aggregate stability, implementing effective management practices is crucial, particularly focusing on cover crops for soil protection and increasing organic matter content.