Changes in Soil Chemical Properties under Crotalaria Cultivation in the Sudanian Zones of Burkina Faso

Abstract

In Burkina Faso, over 65% of arable land is degraded, leading to significant annual losses of nutrients. To address this challenge, this study was conducted to assess the effects of two Crotalaria species on soil chemical properties and to evaluate their potential for restoring degraded soils under smallholder farming conditions. A split-plot experimental design was implemented, combining two factors: Crotalaria species as the main factor and fertilizers (organic, mineral, and their combination) as the secondary factor. Treatments included a control (T0), organic matter alone (OM), Burkina Phosphate alone (BP), and their combination (OM+BP). This study was conducted in 2023 and 2024 on two representative sites of the Sudanian zones (Noumousso in the South and Arbollé in the North). Wet scarification using a hoe (manga) was done in the sites in 2023 and 2024. Once the plots were delimitated, amendments were applied at the rates of 5 t ha-1 of OM and 500 kg ha-1 of BP. Soil was subsequently tilled on the same day, and 300 seeds of the species were evenly sown in the respective subplots. Plot dimensions were 38 m x 16 m, for the main plots, and 5 m x 2 m, for the subplot. Soil chemical analyses performed over two consecutive years revealed a significant improvement in soil properties: increases in pH, C/N ratio, total and available nutrients, exchangeable bases, cation exchange capacity (CEC), and base saturation rate. In the North, pH increased from 5.17 to 5.92 and CEC from 3.7 to 5.6 meq/100 g between the initial year and the second year. In the South, total phosphorus increased more than sevenfold. These results demonstrate that combining Crotalaria species with organo-mineral fertilization sustainably enhances chemical quality of degraded soils. The technology implemented in this study, which led to significant improvements in soil chemical properties over two years, could be considered an improved fallow technology.