Overview

Field studies were conducted in two farmers’ fields in the Asian site in San Jose, Nueva Ecija, Philippines during the 1998 dry seasons. The efficacy of various control strategies against dominant weeds in onion (Allium cepa L.), the major vegetable crop grown after rice (Oryza sativa L.) in rain-fed rice-based cropping systems, were determined. Treatments, consisting of various combinations of herbicides, hand weeding, and cultural practices, varied among fields depending on the onion cultivar grown and the dominant weed species. In spite of the inherent differences in dominant weeds and prevailing weed control practices between the farms, results point to one common observation. Use of a single herbicide and one hand weeding provided comparable weed control and onion yield with those of the farmers’ practice of sequential treatments of two herbicides and two hand weedings. With the farmers’ practice in most cases, a second herbicide application was not necessary either because it was not effective on the dominant weed or because the weed population was reduced by use of traditional cultural practices like tillage or mulching with rice straw. With correct choice of herbicide, the farmers’ practice can be reduced to a single herbicide application and one hand weeding operation.

Results from these studies will be used to develop short- and long-term integrated management strategies based on a rotation systems approach in an effort to reduce expensive and labor-consuming direct weed control inputs, thus decreasing production costs due to weed control in rice-onion cropping systems.