ALLEY CROPPING AND MULCHING WITH ERYTHRINA-POEPPIGIANA (WALP) OF COOKAND GLIRICIDIA-SEPIUM (JACQ) WALP - EFFECTS ON MAIZE WEED COMPETITION

The potential of alley cropping systems to sustain a high productivity with low external inputs and the reduction of maize/weed competition through weed suppression in different alley cropping and sole-cropped mulched systems was studied in Costa Rica at CATIE. Data were recorded eight years after establishment of the experiment. Plant residues of Erythrina poeppigiana trees (10 t/ha dry matter) planted at 6 by 3 m r educed weed biomass by 52%, while Gliricidia sepium trees (12 t/ha dry matter) planted at 6 by 0.5 m reduced weed biomass by 28%, in compari son to controls. Erythrina had a considerable impact on grass weeds, w hile Gliricidia reduced the incidence of some dicot weeds. Weed compet ition significantly reduced maize yield in all systems. Nevertheless w eed suppression contributed to the higher maize grain yield under Eryt hrina and Gliricidia alley cropping of 3.8 t per hectare as opposed to the unmulched control yield of 2.0 t per hectare.