Cover Crops for Weed Management in Organic Vegetables

In the summer of 2000, we received a research grant from the Organic Farming Research Foundation to study over-seeded cover crops in summer vegetables to control weeds. We conducted this study at the WSU Vancouver Research and Extension Unit (WSU VREU), and intended to study the influence of summer over-seeded cover crops on vegetable crop production and weed populations in an organic
farming system over a three-year period. We planted our vegetable crops in May 2000, but by midsummer the weeds in our research field site had overwhelmed our vegetable crop. At that time we had no means to mechanically cultivate our plots (over an acre in size), and we hand weeded plots in an attempt to bring the weeds under control. Due to the extreme weed pressure, our vegetable crops were not
harvestable, and we mowed and disked the plots to prepare for our cover crops. In September 2000 we seeded our cover crop, however within a few weeks the weeds once again dominated the field and we abandoned the study.
In this report we will provide background information about the study, an outline of our materials and methods, and results of our weed survey. Although our study failed to accomplish its original research objectives, the study was successful in impacting the WSU VREU and the overall WSU research agenda:
• This study has served as the foundation for the establishment of the first certified organic agricultural land at Washington State University.
• Due to our plight with weed control, WSU provided us with funds to purchase a small vegetable tractor, cultivator, and flay mower for future vegetable and cover crop research.
• This study provided the basis for a new grant project to establish a cover crop demonstration site for small and organic farmers in our region.
• In conjunction with the WSU Center for Sustaining Agriculture and Natural Resources (WSU CSANR), we have become a major contributor to the WSU Organic Research and Extension initiative and are seeking state and federal funding for this program.
• Also in conjunction with WSU CSANR, we conducted a survey of organic research and
extension programs and will be coordinating a meeting of interested WSU faculty and staff to discuss organic activities.