Suppressing weed growth after wheat harvest with underseeded red clover in organic farming

Authors: Anderson, Randal

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2014
Publication Date: 5/6/2016
Citation: Anderson, R.L. 2016. Suppressing weed growth after wheat harvest with underseeded red clover in organic farming. Renewable Agriculture and Food Systems. 31: 185-190.

Interpretive Summary: Organic producers are interested in no-till systems, but they are concerned about controlling weeds without tillage. We proposed a complex rotation that disrupts weed population dynamics which may help producers no-till in organic farming. This study showed that underseeding annual clovers in winter wheat can control after-harvest weeds. Weed biomass and density of volunteer winter wheat was reduced more than 98%. Also, underseeded clovers reduced seed production of downy brome, a winter annual weed, more than 99%. This tactic will enable producers to no-till between winter wheat and following crops. A no-till system will help organic producers restore and preserve the health of their soils.

Technical Abstract: Organic producers are seeking alternative tactics for weed control so that they can reduce their need for tillage. In this study, we examined cover crop strategies for suppressing weed growth after harvest of wheat. Two cover crop treatments, red clover (mammoth type) or a mixture of oat and dry pea, and a control were compared. Treatments were established in both winter and spring wheat, resulting in 6 treatments arranged in a randomized complete block design. Red clover was underseeded in wheat by drilling in the spring, and the oat/pea mixture was planted in August. Oat was planted uniformly across all treatments the following growing season. The red clover treatment effectively suppressed weeds, reducing post-harvest weed biomass, density of volunteer winter wheat, and seed production of downy brome more than 98% compared with the control. Oat/pea was not effective for weed management, likely because of less fall growth and competition compared with red clover. Underseeding red clover did not affect winter wheat yield, but reduced spring wheat yield 17%. Oat yield, however, was reduced by volunteer crop plants and downy brome infestations. Underseeding clovers in winter wheat may effectively manage weeds and if they winterkill, can replace the need for tillage to control weeds after wheat harvest.