Weed Population Responses to Herbicide-Crop Rotations

Yam (Dioscorea)is an important staple food throughout the Caribbean. Weed competition is a major limitation to production ofyam crops. Because ofreduced interest in herbicide registration for limited-acreage crops such as yam, fanners need alternative weed control methods. Herbicide-crop rotations may become an alternative strategy for weed control in erops such as yarns. The objective of this study was to determine weed population responses and yam production under herbicide-crop rotations. A two year study was conducted at two locations. Treatments were: a) fallow-yarn-yarn, b)bean-bcan-bean-yam, c) cabbage-cabbage-cabbage-yarn, d) bean-cabbage-bean-yam and e) cabbage-bean-cabbage-yam. Weed species were different at Coropal and Isabela. The fonncrSorghum halepense was reduced after the twoyear herbicide-crop rotation but other wecd densities were not different among treatments. At the latter, common weeds were Echinochloa colona, Eleusine indica, Digitaria sanguinalis, and Amaranthus dubius. At both locations weed densities were lower in the final yarn planting than at the beginning of the study and no significant differences in tuber yields were detected among treatments. Data obtained in this study did not provide conclusive results, but dramatic changes in the S. halepense density demonstrate the potential of crop-herbicide rotation for the control of specific weeds.