Physico-chemical characterization of the soils of the watersheds of Boukombe in North-West Benin

This study addresses the specificities of soils in low-income countries. These infertile soils are characterized by low levels of agricultural productivity and the disappearance of long-term fallow, which is gradually giving way to shorter-term fallow and sedentary agriculture. The overall objective was to assess the physico-chemical characteristics of the soils of the Boukombe watersheds in the north-west of Atacora in Benin. Soil studies of 15 farm sites from which soils were sampled at the [0-20] cm horizon with 30 composite samples and statistical analyzes were performed. The results of particle size analysis showed predominance (68%) of a textural dimorphism with a sandy loam character and a relatively stable structure. The soils are generally acidic (pH ≤ 5), sodium in places and poor in Organic Matter (0.3%), particularly in the plateau. Mountain lands have soils richer in OM (4%), but poor in nitrogen with a content of between [0.02-0.14%], the C / N ratio at 3% lower than 12. The contents nutrients and minerals are accumulated at the bottom of slopes (2.23% carbon, 0.14% nitrogen) and at the top of slopes (14ppm of phosphorus) under Fonio. These soils remain in a fragile state, subjecting them to the process of intense erosion. The degradation, silting up and progressive acidification of soils constitute the main constraints of agricultural production, the solution of which is based on restoring their fertility by rehabilitating dikes and removing silt.