Faidherbia albida trees form a natural buffer against millet water stress in agroforestry parklands in Senegal

Description of the subject. In central-west Senegal, agroforestry parklands dominated by Faidherbia albida trees might protect the millet crop against drought and increase agricultural production. Only few studies examined the water relations between the trees and the crop in farmers’ field conditions. Objectives. Our aim was to explore the effect of F. albida trees on millet water potential and the implications for millet yield in F. albida parklands. Method. Sixty-eight F. albida plots scattered in five villages were selected in the 2019 rainy season. In each plot, a pair of millet subplots, “close-to-tree subplot” and “open subplot”, was monitored. We measured millet predawn and midday leaf water potential (Ψp, Ψm), top soil bulk density, water content and temperature, and grain and straw yields at harvest. Results. Pairwise comparisons of Ψp and Ψm of millet indicated better and more stable water status and lower soil temperature and bulk density in close-to-tree subplots. Soil water was sometimes lower in close-to-tree subplots, perhaps because the higher crop biomass in this location resulted in higher water loss through crop transpiration. Tree effects on millet grain and straw yield were positive or null. Correlations between millet yield and Ψp, Ψm measured around flowering were weak. Conclusions. Given their common positive effects on millet water status and yield, F. albida trees could play a key role in promoting sustainable agriculture under the changing climate conditions. Millet yield increase due to the tree proximity was likely due to changes induced by the tree on multiple environmental resources. The interactions of micro-pedoclimatic conditions, livestock and tree management (e.g. density, pruning intensity) on the tree effects should be the focus of future studies.