Morpho – physiological characteristics of Cover crops for analysis of upland rice production in relay intercropping systems

To assess the suitability of Leguminous species in rice intercropping systems, physiological and morphological characteristics of Crotalaria juncea, Cajanus cajan, Mucuna pruriens var. cochinchinensis, Calopogonium mucunoides, Aeschynomene histrix and Stylosanthes hamata were determined in monoculture. C. cajan and S. hamata were selected and intercropped with two upland rice cultivars (WAB56-50, WAB450-24-3-2-P18-HB syn. V4) with different competitive ability, at sowing dates ranging from 0 to 84 days after rice sowing (DARS). In monoculture, C. juncea and C. cajan produced nearly 9 ton dry matter ha, whereas the other species produced below half this amount. Total N in leaf materials varied between 25 kg and 70 kg ha. Based on relative growth rate of the leaves, the height increase rate and total biomass, C. juncea, C. cajan and M. pruriens were identified as potentially most competitive. In intercropping system, a logistic function was adequate to describe rice grain yield, final rice biomass and legume biomass at one week after rice harvest as a function of legume sowing dates. Differences in rice grain yield were significant (P<0.001) due to strong competition effect between 0 and 28 DARS. The yield loss legume biomass relationship showed that C. cajan was the most appropriate legume species in relay intercropping system with upland rice. Keys words : competition, intercropping, nitrogen, Oryza, yield loss