Crop Yield and Soil Organic Carbon in Conventional and No‐till Organic Systems on a Claypan Soil

Core Ideas Soybean in organic no‐till yielded as well as conventional organic. Corn in organic no‐till had lower yield than conventional organic. A crimped cover crop can cause N immobilization and reduced corn yield. Organic crop production is dependent on tillage for weed control, but because tillage can lead to decreased levels of soil organic carbon (SOC) alternative management needs to be explored. This study was conducted in Boone County, Missouri, in 2012 to 2014 to determine the effects of three organic production systems and four poultry compost rates on crop yield and SOC on a claypan soil. The production systems included tillage with no cover crop, tillage with a mowed and incorporated cover crop, and no‐till with a crimped cover crop in a wheat ( Triticum aestivum L.)–corn ( Zea mays L.)–soybean ( Glycine max L.) rotation. Cover crops included cereal rye ( Secale cereale L) and hairy vetch ( Vicia villosa L.). Compost rates were 0, half the recommended rate, the recommended rate, and 1.5 times the recommended rate. Achieving cover crop biomass sufficient for weed suppression was a challenge when soil fertility declined during the study. Corn yield was reduced 30% in 2013 in no‐till plots compared to tilled although plant populations were nearly equal, indicating that N immobilization may be significant in crimped cover crops. When there was adequate soil moisture and weed control from the cover crop, soybean grown under organic no‐till was competitive with tilled treatments. Optimum timing of cover crop crimping for acceptable weed control was more successful in a soybean system compared with corn. Organic no‐till in this study was more successful in soybean and wheat than in corn, when the cover crop biomass was sufficient to suppress weeds.