Cover-crop mulch has long been the weed control tactic of choice for organic no-till corn and soybean systems. But new research featured in the journal Weed Science shows that adding new control tactics can deliver much better results.

To test their theory, scientists planted three-year corn-soybean-winter wheat rotations on plots in Pennsylvania, Maryland and Delaware. A hairy vetch/triticale cover crop mixture preceded the corn plantings, while a cereal rye cover crop preceded the soybean plantings.

 Shallow, high-residue cultivation during the no-till corn and soybean phases was found to decrease weed biomass relative to the uncultivated control plots by as much as 62 percent in corn and 78 percent in soybean crops.  In instances where weed suppression during the crop phases of a rotation proved less than optimal, adding winter grain or perennial forages prevented rapid increases in the weed seedbank.

Researchers also tried delaying crop planting dates in order to extend the cover-crop growing cycle and produce a greater mulch biomass. But they discovered there were tradeoffs. Common ragweed became less abundant as corn and soybean planting dates were delayed, but giant foxtail and smooth pigweed increased as a percentage of total weed biomass.

The net takeaway:  For better weed control in organic crops, adopt multiple weed management tactics, and focus on cover crop management instead of biomass production.

Want to find out more? Read the article “Integrated Weed Management Strategies in Cover Crop-based, Organic Rotational No-Till Corn and Soybean in the Mid-Atlantic Region,” available in Weed Science Vol. 66, Issue 1.

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