Influence of agroforestry systems on earthworm diversity and soil properties in a Sudano-Sahelian landscape

Abstract

Agroforestry systems promote a range of ecological base management to support sustainable agriculture. However, the influence of agroforestry management on soil biodiversity is still poorly investigated in Sudano-Sahelian landscapes. This study aims to guide sustainable management for soil biodiversity conservation in agroforestry systems by determining the drivers of earthworm diversity with their abundance and corresponding soil properties. Nested sampling following three management systems (agroforestry fallow, agroforestry intercropping, agroforestry grazing) and the protected area as a baseline, were designed for data collection in a Sudano-Sahelian landscape. Earthworm inventory and soil sampling (0–10 cm), coupled with a survey focusing on the cropping and fallowing duration with other agricultural practices (herbicide use, soil tillage), were conducted on the farm. The soil analysis included soil texture, bulk density and a suite of chemical analyses (pHKCl, C and N, available macro and micronutrients). The data were analyzed using generalized linear models (GLMs) and ANCOVA to determine the effects of agroforestry systems on earthworm abundance and soil properties. A Principal Component Analysis (PCA) was performed to determine the relationship between the species richness of earthworms, agroforestry systems and soil properties. The results showed a diversity of five species belonging to the endogeic and epigeic ecological groups numbered at 7 ± 3 to 22 ± 10 individuals m−2 (mean ± standard deviation). In agroforestry fallow systems, earthworm diversity and abundance were both highest, and the abundance increased with the fallow duration. The prolongation of cropping duration coupled with herbicide use in agroforestry intercropping systems decreased significantly the abundance of earthworms. Agroforestry grazing systems increased significantly soil C, N and available nutrients, but the abundance of earthworms and species richness were the lowest likely due to soil destructuration by trampling. Overall, soil texture controlled the species richness of earthworms. Fallow management and agricultural practices with fewer herbicide use and soil destructuration, are essential to improve earthworm abundance and diversity.