Evaluation of Some Herbaceous Legumes for Use as Green Manure Crops in the Rainfed Rice Based Cropping System in Northern Ghana

Five herbaceous legumes, Mucuna pruriens var. nagaland, Mucuna pruriens var. cochichinensis, Crotalaria retusa, Crotalaria juncea and Canavalia ensiformis were evaluated as green manure crops for rain fed rice at Nyankpala, Ghana in the interior guinea savanna zone of Ghana during the 2003 and 004 cropping seasons. The Mucuna and Canavalia were planted at a spacing of 20 x 60 cm. Crotalaria was drilled at a seeding rate of 50 kg ha-1 with 20 cm in between the rows. At flowering, the legumes were incorporated into the soil and rice planted. Nitrogen fertilizer was applied at 0, 0 or 60 kg ha-1 three weeks after planting rice. The treatment combinations were laid out in a factorial experiment in Randomized Complete Block Design (RCBD) with three replications. Results have shown that nodulation differed significantly among the legumes. Canavalia ensiformis (CE) gave the highest biomass followed by Mucuna pruriens var nagaland (MN). Mucuna pruriens var. nagaland (MN) gave the highest N accumulation. Incorporation of Mucuna pruriens var nagaland plus fertilizer application (30 kg N ha-1) enhanced yield of rice. It is recommended that for increased yield of rice, farmers in Northern Region of Ghana could integrate Mucuna pruriens var nagaland (MN) into their cropping system with fertilizer N application not exceeding 30 kg N ha-1.