Submitted to: Weed Science Society of California Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2007
Publication Date: July 1, 2007
Citation: Steenwerth, K.L., Baumgartner, K., Veilleux, L. 2007. WEED COMMUNITY COMPOSTION IN RESPONSE TO ORGANIC AND CONVENTIONAL WEED CONTROL PRACTICES IN A CALIFORNIA VINEYARD. Weed Science Society of California Meeting Proceedings. Technical Abstract: Integrated weed management (IWM) employs multiple tactics to control weed infestations, and can be useful in reducing problematic weeds. IWM in California vineyards typically involves the integration of post-emergence herbicides and pre-emergence herbicides, with less emphasis on incorporation of non-chemical methods. Therefore, the aim of this research was to compare the organic weed control practice, soil cultivation, to the conventional practice, applications of the herbicide, glyphosate, in terms of their effects on weed community dynamics in a vineyard system. Objectives were to: 1) evaluate the efficacy of the practices in reducing weed biomass, 2) characterize the weed community, 3) monitor vine yield, growth, and nutrition under the influence of the practices, and 4) determine the effects of the practices on soil biological activity. The experiment was conducted in a commercial winegrape vineyard in the Napa Valley of northern California from 2003 to 2005. The annual treatments were winter-spring glyphosate, spring cultivation, fall-spring cultivation, and fall cultivation-spring glyphosate, and were applied to the berm. Glyphosate1 [N-(phosphono-methyl-glycine), Roundup UltraMAX] was applied at label rates with a tractor-mounted, 1.2-m-wide, boom sprayer with two fan-type nozzles directed beneath the vines on both sides of the tractor. Cultivations were done with a Radius Weeder2 (Clemens cultivator). In general, cultivation alone was not as effective as glyphosate, but the overall effectiveness of each treatment in reducing weed biomass was not consistent among all years. For example, lower weed biomass occurred in the glyphosate-only treatment in two of three years. However, given that two passes with the Clemens cultivator (i.e., fall-spring cultivation) decreased weed biomass relative to one pass, it is possible that additional passes could bring about further reductions. Pairing fall cultivation with glyphosate was as effective at reducing weed biomass as two glyphosate applications in two of three years, suggesting that substituting a glyphosate application with cultivation may be an effective method of reducing herbicide use in vineyards.