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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #313671
Title: Using cover crops to alleviate compaction in organic grain farms: effects on weeds and yields

Author
item WELCH, RACHEL - University Of Illinois
item Davis, Adam
item MASIUNAS, JOHN - University Of Illinois
item BEHNKE, GEVAN - University Of Illinois
item VILLAMIL, MARIA - University Of Illinois

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2015
Publication Date: 1/15/2016
Citation: Welch, R., Behnke, G., Davis, A.S., Masiunas, J., Villamil, M.B. 2016. Using cover crops to alleviate compaction in organic grain farms: effects on weeds and yields. Agriculture Ecosystems and Environment. 216:322-332.

Interpretive Summary: Physical control of weeds in organic systems can often come at the expense of soil quality goals in organic production systems. Organic producers heavily rely on tillage for mechanical weeding, creating compacted areas ideal for weedy species, and forming a vicious cycle of tillage, compaction and increasing weed populations. In an effort to address the concerns of certified organic farmers from Illinois, we explored the effect of selected cover crops in compacted and non-compacted areas of their farms on weed populations and crop yields in a participatory on-farm research approach. Use of a mixed cover crop community of forage radish, hairy vetch and cereal rye reduced weed counts by 37% and reduced weed biomass by 48% in compacted areas and 75% in non-compacted areas in comparison to their respective controls without cover crops. Use of this cover crop mixture was associated with a 20% reduction in soybean yields on non-compacted field areas in drought conditions, but did not affect crop yield in moist conditions. Cover crops may have weed suppressive benefits in organic field crop production systems, but enhanced weed management may come at a cost of increased competition with the main crop, depending upon soil physical conditions.

Technical Abstract: Organic producers heavily rely on tillage for mechanical weeding, creating compacted areas ideal for weedy species, and forming a vicious cycle of tillage, compaction and increasing weed populations. In an effort to address the concerns of certified organic farmers from Illinois, we explored the effect of selected cover crops in compacted and non-compacted areas of their farms on weed populations and yields in a participatory on-farm research approach. The experimental layout was a split-plot arrangement of compaction and cover crop treatments with two replications set up at four locations around Illinois. The main plot treatments were compacted (CP) versus non-compacted areas (NCP), and the sub-plot consisted of four levels of cover crops treatments: a control left fallow (C), forage radish (Raphanus sativus L.) (FR), forage radish and buckwheat (Fagopyrum esculentum ) (FRbw); and forage radish with hairy vetch (Vicia villosa Roth L.) and cereal rye (Secal cereale L.) (FRhvr). Farmers mutually agree on planting soybean (Glycine max L. Merr.) in 2012, and corn (Zea mays) in 2013. Cover crop counts were conducted every fall prior to winterkill and spring before termination by tillage. Weed counts, along with their biomass and species identification were collected prior to cash crop planting and during the growing season, while cash crop yields were determined every fall. The FRhvr treatment reduced weed counts by 37% and reduced weed biomass by 48% in the CP areas and 75% in the NCP areas in comparison to their respective controls without cover crops. While weed suppression was effective with the overwintering cover crop mixture of FRhvr, soybean yields were significantly reduced by about 20% in NCP areas of the farms in 2012 while no effect on corn yield was recorded in 2013. Widespread drought conditions during 2012 likely hastened competition between cash and cover crops for scarce water resources in NCP areas whereas CP areas prevented this effect by holding more water within their soil profiles. This trend was verified with our scaled corn and soybean yields. Our findings suggest the rotations with cover of forage radish/hairy vetch/rye can significantly suppress weed populations yet can potentially decrease yields in dry years.