Submitted to: Western Society of Weed Science Research Reports
Publication Type: Research Notes
Publication Acceptance Date: 11/21/2015
Publication Date: 3/7/2016
Citation: Anderson, R.L. 2016. A suggestion for planning cover crop mixtures: zones of occupancy. Western Society of Weed Science Research Reports. p. 122-136.
Interpretive Summary: Producers are using cover crops to improve soil health. They are interested in mixtures of cover crops, but some mixtures can yield considerably less than sole crops. We showed in this study that considering crop canopy structure may help plan mixtures that increase biomass production. The cover crop canopy can be divided into 3 zones, high (15-20 inches tall), mid (10-15 inches) and low (less than 10 inches). Planning cover crop mixtures to have one species occupy each zones may lead to higher biomass. A successful mixture was oat + dry pea + oilseed radish. When mixtures had an in-balance of species among zones, biomass declined because of interspecies competition.
Technical Abstract: Producers may be able to improve the competitiveness of cover crop mixtures by selecting species to occupy zones in the cover crop canopy. This suggestion is based on a study where we compared four cover crop treatments, 1, 3, 6, and 9 species mixtures, for biomass production. Treatments were established in August, following spring wheat harvest. Biomass was harvested 9 weeks later. The most productive treatment was the oat-dry pea-oilseed radish mixture. Species of this mixture occupied different levels (zones) in the canopy, which we believe minimized interspecies competition to improve production. Cover crop mixtures of 6 and 9 species yielded 30% less biomass, which we attribute to unequal distribution of species in zones of the canopy. We encourage producers to consider canopy architecture and zones of occupancy when planning cover crop mixtures.