Screening legume green manure for climatic adaptability and farmer acceptance in the semi-arid agro-ecological zone of Uganda

Crop yields in Uganda are severely limited by declining soil fertility. Nitrogen (N), phosphorus (P) and soil organic matter (SOM) are the most limiting factors, yet legume green manures are known to fix N-2 and increase SOM. Legume green manure technology has proved suitable for smallholder and subsistence farmers in sub-Saharan Africa. In Uganda, the spread of the technology has so far been concentrated in the central and eastern part of the country. Therefore, this study aimed at scaling out the legume green manure technology in the western semi-arid and cattle corridor zone of Uganda through on-farm researcher-designed, researcher/farmer managed village trials. For this purpose the six legumes namely Crotalaria grahamiana, Crotalaria ochroleuca, Mucuna pruriens, Canavalia ensiformis, Lablab purpureum and Tephrosia vogelli were tested in plot of 10 m by 10 m in a randomized complete block design whereby each farm site represented a replicate. Six months after planting of the legumes, farmers were individually asked to select their preferred species and to name the reasons for their choice. Subsequently, the legume biomass was determined and incorporated in the soil prior to planting maize. C. ensiformis and T vogelli were the most and least preferred species, respectively, C. ensiformsis yielded the highest (5.2 t ha(-1)) and T vogelli the lowest (2.0 t ha(-1)) biomass. Highest maize grain yields were obtained from plots of M. pruriens (3.5 t ha(-1)), but they were not significantly different from those of C. ensiformis with 3.4 t ha(-1). Incorporation of the natural fallow vegetation led to the lowest maize grain yields (1.9 tha(-1)).