Impact of crop production on selected soil physicochemical properties in semiarid climate zone of Benin, West Africa

Land and soil degradation caused by arable farming affects the livelihoods of the local population in semiarid climate regions, such as in West Africa. In particular, cotton (Gossypium hirsitum L.) production is a crucial driver of soil degradation. However, the extent of soil degradation under cotton compared to other crops and the natural vegetation as a possible benchmark for non-degraded soil needs to be better understood. Topsoil at 0–10 cm depth from fields of cotton (G. hirsitum), three cereal species (maize [Zea mays L.], millet [Eleusine corocana L.] and sorghum [Sorghum bicolor (L.) Moench]), three legume species (cowpea [Vigna unguiculata L.], peanut [Arachis hypogaea L.] and soybean [Glycine max L.]) and woodland as natural vegetation were analyzed for soil porosity, water stable aggregates, water holding capacity, pH, electrical conductivity, soil organic carbon, total nitrogen and total sulfur. A simple soil degradation index was derived from the measurements. Findings revealed that the topsoil of cereal crop fields was more compacted, with less porosity, than the topsoil of cotton and legume crop fields. However, the soil degradation index was higher in the cotton fields than in the legume and cereal fields. The soil fertility was reduced on cropland compared with natural vegetation, following the order of woodland > legumes > cereals > cotton. Integration of tree components in agricultural production systems through agroforestry may provide an option to improve soil fertility in semiarid regions.