Evaluating the impact of different agropastoral practices on wind erosion in western Sahel

Abstract

In the Sahel, nutrient-poor sandy soils are vulnerable to wind-driven erosion and can be further degraded if left unprotected. As more than 60 % of the Sahelian population depends on rainfed agriculture, land degradation is a primary concern. In the last 60 years, climatic and socio-economic factors have thoroughly modified the Sahelian cropping systems. Understanding the interaction between land uses, agropastoral practices and wind erosion is crucial.

This study aims to estimate the effect of the main types of land uses and management that occurred in the Senegalese groundnut basin in the last decades on potential wind erosion of soil at the field scale. In-situ measurements of meteorological data, vegetation and horizontal fluxes of aeolian sediments were monitored on the land uses of a typical Sahelian landscape (groundnut plot, four fallows, four millet plots), each with contrasting and representative land managements, creating an unprecedented dataset in this region. We developed a modeling approach combining vegetation models with a horizontal flux model, calibrated on the gathered data. This modeling approach was able to reproduce existing measurements and is intended eventually to upscale fluxes of aeolian sediment at the landscape to regional scales.

Measurements of horizontal fluxes of aeolian sediments ranged from 538.7 kg.m⁻¹.year⁻¹ on bare soil to almost no flux on fallows. Simulations accurately represent the dynamics and order of magnitudes of erosive events despite having a strong sensibility to the aerodynamic roughness length of the soil surface. The comprehensive simulation of the impact of groundnut, millet (with and without residues) and fallows on potential wind erosion highlights the impact of dry vegetation cover, especially weeds, after the rainy season.