POTENTIAL OF PASTURE LEGUMES IN LOW-EXTERNAL-INPUT AND SUSTAINABLE AGRICULTURE (LEISA). 1. RESULTS FROM GREEN MANURE RESEARCH IN LUAPULA PROVINCE, ZAMBIA

Abstract

In view of soil fertility problems and financial constraints identified in small-scale farming, on-station investigations on Low-External-Input and Sustainable Agriculture (LEISA) were started by the Farming Systems Research Team Luapula Province (FSRT-LP) in order to assess the potential of three annual and six perennial pasture legume species for green manuring purposes. Rhodes grass (Chloris gayana cv NIRS Boma) was used as a control. Over two seasons, a pasture legume-maize rotation trial was established. Different mineral fertilizer amounts were applied to the maize. Of all the species and cultivars tested, the perennial glycine (Neonotonia wightii cv Cooper) had the strongest green manure effect when no mineral fertilizer was applied. Of the annual pasture legumes, sunn hemp (Crotalaria juncea cv. NIRS 3) and velvet bean (Mucuna pruriens cv. NIRS 16) showed the greatest green manure potential at zero mineral fertilizer level. There were strong indications that the carbon:nitrogen ratio influenced the green manure potential of a species more than its ability to produce biomass. The need to assess the economics and sustainability of current mineral fertilizer practices on maize has been identified.