ORIGINAL PAPER Maximising yield benefits from dual-purpose cowpea E. Dube & M. Fanadzo Received: 7 August 2013 /Accepted: 7 October 2013 /Published online: 26 October 2013 # Springer Science+Business Media Dordrecht and International Society for Plant Pathology 2013 Abstract Cowpea (Vigna unguiculata [L.] Walp.) is con- sumed by many subsistence farmers across the African conti- nent 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 bene- fits 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 ef- fects. 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 pro- ductivity of cowpea. Keywords Cowpea leaf . Cowpea grain . Food security . Protein . Subsistence farmers Introduction Considering all the protein sources that might possibly help Africa’ s malnourished millions, the leading locally domesti- cated candidate is cowpea (Vigna unguiculata [L.] Walp.) (Singh et al. 2003; National Research Council 2006). Although hardly known in global terms, cowpea constitutes sub-Saharan Africa’ s most widely planted native legume and is the second most important grain legume continent-wide after peanut (Arachis hypogaea ) (National Research Council 2006). Cowpea grows well in poor soils that have more than 85 % sand, less than 0.2 % organic matter and low levels of phosphorus (P) (Singh et al. 2003). Furthermore, many cow- pea cultivars can withstand drought and have short growing periods, making them very attractive to farmers in marginal, drought-prone areas that have low rainfall and poorly devel- oped irrigation systems (Hallensleben et al. 2009). Cowpea is regarded as a “poor man’ s crop” but, in a sense, it is a fulcrum for leveraging Africa’ s basic nutrition and has been called “a nearly perfect match for the African soil, weather and people” (National Research Council 2006). The crop is consumed in many forms. Young leaves, green pods, green leaves and dried leaves are used as vegetables whereas dry seeds and roots are used in a variety of food preparations (Nielsen et al. 1997). In the humid tropics of Africa, cowpea is grown mainly for its leaves but, elsewhere in Africa, the leaf and the seed are generally accorded equal importance. Problem statement In subsistence farming in Africa, the traditional practice of harvesting young leaves is frequently identified as one of the factors responsible for reduction in yield and quality of the grain (Madamba 2000; Nyakanda et al. 2004; Ibrahim et al. 2010; Matikiti et al. 2012). It is also suspected that the nega- tive effects of this practice may extend to the reduction of other cowpea benefits such as nodulation, nitrogen (N) fixa- tion and soil fertility improvement. The term ‘dual-purpose cowpea’ has been coined to describe a system whereby cow- pea leaves are harvested for vegetable use followed later by grain or pods from the same crop. Recommendations on proper harvest and crop management strategies are required in order to allow subsistence farmers to fully exploit the substantial nutritional and economic benefits of dual-purpose E. Dube (*) ARC - Small Grain Institute, Private Bag X29, Bethlehem, South Africa e-mail: dubee@arc.agric.za M. Fanadzo Department of Agriculture, Cape Peninsula University of Technology, Private Bag X8, Wellington 7654, South Africa Food Sec. (2013) 5:769–779 DOI 10.1007/s12571-013-0307-3