Controlling Weeds With High Residue Cultivation in Cover Crop-Based Organic Rotational Soybean Production.

Rolled cereal rye cover crops produce surface mulches that are adequate at suppressing many summer annual weeds. However, when annual weed seed banks are high or if perennial weeds are present, a multi-tactic approach is required. High-residue cultivators have the potential to provide supplemental control in these heavy mulches. Research trials were set up to determine optimum timing of high residue cultivation for weed control in roll-killed cereal rye mulches. Cereal rye biomass, weed control (density, biomass and diversity), soybean population, and soybean yield were assessed in high residue cultivated plots and compared to those hand-weeded and no cultivation. The high-residue cultivator was tested at three timings: 3-4-wk, 5-6-wk, or 7-8-wk after soybean planting between 2010 and 2012. Cereal rye biomass was lowest in 2011 (dry year) and thus weed biomass was 3-fold higher. Our results show that two out of the three years, cultivation improved weed biomass control and subsequent soybean yield. There was no significant effect of cultivation on soybean population per ha when compared to no cultivation or hand-weeded treatments. While there was a significant effect of cultivation on weed biomass, this effect did not consistently translate to improved soybean yield in years where water was limited.