Choosing and managing cover crops to improve weed management in reduced tillage organic vegetable production
CSANR Project 097
Reduced tillage can improve soil quality and reduce fossil fuel use. Adopting reduced tillage in organic production poses challenges because farmers rely on tillage as a primary means of weed management and for incorporating soil amendments to maintain soil fertility and quality. Recent research on organic reduced tillage has focused on mechanically terminated and mulched cover crops to reduce weed pressure. Our data show potential for rolled or flailed cover crops to reduce weed pressure and weeding labor in organic vegetable production in western Washington, but questions remain regarding cover crop selection and management effects on weeds and soil fertility. Project objectives are: 1. Evaluate the effects of cover crop termination time, mulch thickness, and soil N on weed populations in organic reduced tillage systems. 2. Use cereal and legume cover crops to evaluate how N immobilization/mineralization from terminated cover crops affects weed suppression in reduced tillage systems. A field experiment will be duplicated at Puyallup and Mt. Vernon, WA to examine cover crop mulch effects on nitrate, light levels, and weed populations. Cover crops include Strider barley, Lana vetch, and a blend of barley and vetch. Seven additional cover crops and blends will be compared at Puyallup for mulch effects on weed populations and soil nitrate. A greenhouse experiment will evaluate how cover crop mulch depth and nitrogen level affect weed emergence. Guidance tools will be developed from the results, including extension publications, and “spider diagrams”, which are visual representations of weed dynamics that will aid growers in implementing reduced tillage cover crop systems.