Dry matter of green manure and control of weeds at different sowing legume densities

The objective of this study was to evaluate the dry matter yields of Calopogonium mucunoides, Stizolobium aterrimum, Stizolobium deeringeanum variety "rajada", Canavalia ensiformis, Cajanus cajan, Crotalaria breviflora and C. spectabilis in relation to the sowing densities of 10, 20, 40, 80 and 160 seeds m(-2), and the yield of weeds grown in these legume densities. This study was carried out from May to August 1996, in a coastal tableland area of the Antonio Martins Experimental Station (EMDAGRO/Embrapa-CPATC), at Lagarto, State of Sergipe, Brazil. The number of survival plants and the dry matter yields were determined when each species reached the flowering stage. The highest increments of dry matter yield in response to increasing levels of sowing density were observed in plants of Crotalarin spectabilis and C. breviflora followed by C, mucunoides, S. aterrimum and S. deeringeanum. A negative response to the increasing sowing densities was observed in Canavalia ensiformis and sowing densities did not affect the dry matter yield of Cajanus cajan plants. Linear and positive responses of C. spectabilis, C. breviflora and C, mucunoides, and quadratic responses of C. ensiformis, C. cajan and S. deeringeanum were obtained for number of plants in response to increasing sowing density. No equations were found to express the relation between the number of survival plants and sowing densities of S. aterrimum, but the survival of this species at high populations was very low. S. aterrimum and C. ensiformis showed the best weed inhibition, even in the lower sowing densities.