Potential of biomass transfer technologies in sustaining vegetable production in the wetlands (dambos) of eastern Zambia

Farmers grow vegetables widely during the dry season in wetlands known locally as dambo s in southern Africa. Declining soil fertility is one of the major factors limiting smallholder vegetable production in the dambo s of eastern Zambia. An experiment was initiated with 43 farmers with the objective of assessing the agronomic and economic feasibility of foliar biomass of gliricidia ( Gliricidia sepium ) and leucaena ( Leucaena leucocephala ) for production of cabbage, onion and a subsequent maize crop during the dry season. The treatments were, on a dry-matter basis, 8 and 12 t ha −1 gliricidia, 12 t ha −1 leucaena and 10 t ha −1 manure+half the recommended fertilizer rate, inorganic fertilizer at recommended rate, and a control without any inputs. Direct field measurements and informal enquiries were used for evaluating the effects of different treatments. The highest cabbage and onion yields were obtained from manure+half-rate fertilizer application. The gliricidia biomass transfer technology produced cabbage, onion and maize yields comparable with the full fertilizer application. In both cabbage and onion, manure+fertilizer gave generally higher net incomes. Biomass transfer also recorded higher net incomes than the control, and required lower cash inputs than the fully fertilized crop. Net incomes of the biomass treatments were substantially reduced by the labour costs for pruning and incorporation of the biomass. The results indicate that the gliricidia biomass transfer technology could be used as an alternative to inorganic fertilizers for vegetable production in dambo s.