Characterization of growth, nitrogen accumulation and competitive ability of six tropical legumes for potential use in intercropping systems

Legume cover crops can be successfully used as intercrop or relay crops in low-input farming systems. To select appropriate species for intercropping, experiments were conducted in the savannah zone of Côte d'Ivoire during the wet seasons of 1997 and 1998 to determine the growth and nitrogen (N) accumulation of six cover legumes as well as the characteristics indicative of competitive ability. The species included the erect growing Crotalaria juncea and Cajanus cajan, the creeping species Mucuna pruriens var. cochinchinensis and Calopogonium mucunoides and the bushy herbaceous species Aeschynomene histrix and Stylosanthes hamata. Marked differences in phenology were observed as S. hamata and C. juncea flowered around 45-55 days after sowing (DAS) and the other species around 80-95 DAS. C. juncea and C. cajan produced close to 9 ton dry matter ha1, whereas the other species produced less than half this amount. The average estimated amount of accumulated N, based on leaf material, was around 70 kg ha1 for all species except S. hamata and A. histrix, which only produced around 25 kg ha1. Based on morphological characteristics, C. juncea, C. cajan and the short-lived M. pruriens were identified as potentially most competitive, indicating that productivity and competitive ability are strongly linked. The implications of these findings for intercropping systems in upland rice production are discussed.