Best-Bet Legumes for Smallholder Maize-Based Cropping Systems of Malawi

Malawi’s burgeoning population and dependence on maize (Zea mays L.) as a staple food had led to continuous maize cultivation and declining soil organic matter levels. Devaluation of the Malawi Kwacha and removal of fertilizer and maize price subsidies have contributed to increased interest in legumes as sources of human nutrition and soil fertility in the N-depleted soils of Malawi. However, the intense land pressure means that any leguminous system must be competitive with continuous maize in terms of calorie production per hectare and economic net benefits. Legumes that can satisfy economic and food security criteria while still improving soil fertility are termed ‘best-bet’ systems because smallholder maize producers are more likely to adopt them. Several best-bet leguminous systems have been identified in Malawi based on these criteria: grain legume-maize rotations with groundnut (Arachis hypogaea L.) or promiscuous soybean (Glycine max [L.] Merr.), legume/maize intercrops with pigeon pea (Cajanus cajan [L.] Millsp.) or fishbean (Tephrosia vogelii Hook. f.), and velvet bean (Mucuna pruriens [L.] DC.)- maize rotations. Recent research in Malawi indicates that grain legume rotations with CG7 groundnut and Magoye soybean (a promiscuous variety able to fix atmospheric N2 without inoculation) are superior to continuous unfertilized maize in terms of calories produced and economic net benefits (on a cash basis). Constraints to increased adoption of these grain legumes include seed costs for groundnut, fluctuating market prices for soybean and practical difficulties with residue incorporation for both species. Pigeon pea and Tephrosia both exhibit a temporal complementarity of resource use with maize because of their use of residual soil moisture. Thus they are well suited to intercropping systems because maize yield is not reduced. Disadvantages for pigeon pea cultivation include a poor seed yield for long-duration pigeon pea in central and northern Malawi and livestock damage in northern Malawi. Tephrosia is not browsed but does not have the food value of pigeon pea. Mucuna has consistently generated a higher seed yield and total biomass than other annual legumes studied in Malawi. However, if Mucuna is managed as a grain legume rather than a green manure, the seeds must be processed extremely carefully for human consumption. No single leguminous cropping system will be a panacea for a country as agro-ecologically diverse as Malawi. Much recent research and extension effort has gone into comparisons of best-bet legumes that present farmers with as many options as possible so that they can choose cropping systems best suited to their needs. If challenges such as improved human utilization and increased market demand are met, these legumes will play an important role in diversifying Malawian farming systems and ensuring improved household food security.