Maximising yield benefits from dual-purpose cowpea

Cowpea (Vigna unguiculata [L.] Walp.) is consumed by many subsistence farmers across the African continent as a cheap source of quality protein. Harvest of cowpea leaves as a vegetable as well as grain from the same plant (dual-purpose) is a primary goal for farmers, which allows them to exploit the nutritional benefits of both. The leaves are consumed in a variety of traditional dishes, or dried for use in the dry season. However, leaf harvest practices by farmers are among the leading causes of poor grain yield and quality. These negative effects can extend to reduction in other benefits of cowpeas such as nitrogen fixation and soil organic matter improvement. This paper critically reviews the effects of leaf harvesting practices on cowpea crops and options available to subsistence farmers to mitigate the negative effects. Recommendations on appropriate timing, duration and intensity of leaf harvesting are then provided, together with agronomic strategies for maximising benefits. Information gaps are also highlighted with the aim of guiding future research programmes for the improvement of the food productivity of cowpea.