Effect of Compost Based Local Substrates on Soil Fertility and Agronomic Performance of Cowpea (Vigna unguiculata (L.) Walp) in Burkina Faso Semi-Arid Zone.

Declining soil fertility remains a major constraint for farmers in the semi-arid Sahelian regions. This study assessed the effects of increasing rates of compost combined with zaï pits on the productivity of the cowpea variety “Komecallé” (Vigna unguiculata (L.) Walp) and on soil fertility. Soil samples and agronomic parameters were collected using a completely randomized block design with four treatments replicated four times in Pabré, Burkina Faso: T0 = Zaï only; T1 = Zaï + 1 t ha⁻¹ of compost; T2 = Zaï + 2 t ha⁻¹; and T3 = Zaï + 3 t ha⁻¹. Analysis of variance (ANOVA) and Tukey’s HSD test at the 5% significance level were applied. Results revealed that mineral nitrogen increased by 18,9%, 23,9%, and 22,1%; available phosphorus by 21,3%, 44,7%, and 23,6%; and available potassium by 21,7%, 18,2%, and 22,6% under T3, T2, and T1 respectively. Haulm yields increased significantly by 65% under T3, while grain yields increased by 82% under T2. The treatment T2 (2 t ha⁻¹ compost) proved to be the most effective option for enhancing both productivity and soil fertility. The valorization of local substrates could contribute in soil fertility and cowpea production policies in semi-arid regions and reduce fertilizers cost for farmers.