EFFECT OF DIFFERENT STORAGE METHODS ON THE QUALITY CHARACTERISTICS OF COWPEA GRAINS
Cowpea is a food grain legume that plays an important role in the lives of millions of people in Africa and other parts of the developing world. The crop is also a valuable and dependable commodity that produces income for many small holder farmers and traders in Sub-Saharan Africa (Langyintuo et al., 2003). In West Africa, cowpea is grown mostly in subsistence farming systems and on a small scale in the lowland dry Savannah and Sahelian regions. However, cowpea cropping systems are changing to monocropping as the crop’s economic importance increases. The cultivation of cowpea in Ghana is carried out mostly in the transitional zone of northern guinea savannah zone of Northern, Upper East and Upper West Regions. The major season for cowpea cultivation is from May to August. However, a few resourceful farmers who can protect their cowpea plants against field pests plant around late July or early August, and harvest in October. Production of cowpea in Ghana is among the lowest in the world in terms of yield, averaging 310 kg/ha (IITA, 2009). Hence, efforts have been made to improve cowpea production in Ghana through various means including the introduction of new varieties.
In Africa, cowpea is the most popular legume and the largest part of the world production originates from this continent. Cowpea is adapted to stressful environments where other crops fail. It is a food security crop in the semiarid zone of West and Central Africa (WCA) which ensures farm household subsistence food supply even in dry years. Recently, FAO, (2009) estimated the world production area as 5.6 million hectare, of which at least 90% is in West and Central Africa, and the annual world grain production is estimated at 2.7 million tonnes. World cowpea
production was estimated at 3 319 375 MT and 75% of that production is from Africa (FAOSTAT, 2000). The principal cowpea producing countries are Nigeria, Niger, Senegal, Ghana, Mali, and Burkina Faso (FAOSTAT, 2000). Nigeria is the largest cowpea producer in West Africa. Post-harvest insect pest of cowpeas (Vigna unguiculata (L.) Walp) in sub-Saharan Africa is one of the major factors that reduce the nutritional quality and economic value of the grain (FAOSTAT, 2000). In anticipation of losses during storage producers sell at harvest when the price is lowest. The principal pest is the cowpea bruchid, Callosobruchus maculatus (F.), but other bruchids cause losses as well. The losses have been attributed to improper methods used in grain storage. The high losses occurring after storage compels wholesalers and retailers not to buy in large quantities and store for future sale/usage. Many cowpea chain agents are not sure of what storage methods to use to reduce economic losses. The nutritional benefits associated with cowpea consumption are clear and cannot be over emphasized. Since cowpea is locally consumed in so many forms in Ghana, there is the need to derive maximum benefit from its production to boost the nutritional needs of the populace. The various stakeholders involved in the distribution chain therefore needs information on the various storage methods and how they impact the quality of the grains after storage especially Nhyira, Asomdwee, Adom, Soronko and Tona varieties which is the most preferred varieties and highly nutritious in Ghana. As a result of these uncertainties further research is needed to identify an acceptable storage method and establish the possible effects of the various storage methods on the quality of cowpea grains.