Cowpea plays a considerable role in the nutritional balance and rural economic of Burkina Faso. However, its farming is marked by yields instability related to drought and soil depletion of nutrients, particularly nitrogen and phosphorus. In this study factorial trials were carried out in 12 farmers' fields in the northern Soudano-sahelian region of Burkina Faso, in view to compare nodulation and growth of cowpea without and with rock phosphate (25% P and 10% Ca) applied at the dose of 313 kg ha-1. Although a large variation was observed between trial sites, the cowpea nodule dry weight increased from 21±2 without rock phosphate to 30±3 mg plant-1 with rock phosphate. The shoot biomass increased from 9±2 g to 13±1 mg plant-1, and grain yield from 564±1 kg ha-1 to 687±2 kg ha-1. However the benefit of the Burkina rock phosphate was much higher in trials where the nodulation of cowpea was the highest. It is concluded that the supply of Burkina rock phosphate could significantly improve the symbiotic nitrogen fixation and the yield of cowpea in sub-Saharan areas of Africa. (Texte intégral)