Success and Challenge with Reducing Tillage in an Organic Cropping System.

Organic farmers in the northeastern US face many challenges including farming on erodible soils with vulnerable watersheds and the strong desire to use sustainable farming practices. Historically, organic crop farming has relied heavily on tilling the soil to prepare the seedbed and to help manage weeds. The negative impacts of tillage have stimulated a growing interest in identifying and adopting practices that are less tillage intensive, while at the same time providing sufficient weed control in organic crop production systems. The Reduced-tillage Organic Systems Experiment (ROSE) was conducted at three sites in the mid-Atlantic region from 2011 to 2013 and provides a unique opportunity to explore weed suppression in cover crop-based, organic rotational no-till corn and soybean production across a relatively wide range of environmental conditions. The study examined a corn-soybean-wheat rotation using hairy vetch-triticale before corn and cereal rye before soybean and although slightly different management practices were used to accommodate differences across the region, base management tactics were the same. The objective of this project was to evaluate the effects of planting date, corn and soybean cultivar, and high-residue cultivation on weed suppression, crop yield, and other metrics of cropping system performance.

Over the three years of the rotation, we observed some common and divergent results and trends depending on year and location.  Overall, site-specific adaptations were successful and weed suppression in organic no-till planted corn and soybean ranged from excellent to complete failure. Prior to implementing the experiment, additional weed control tactics were implemented at the PA and MD sites to reduce weed populations in the soil seedbank. Weed suppression was consistently good at the PA site, but more variable at the MD site. At the DE site, weed suppression was better in corn than soybean, and large populations of yellow nutsedge, broadleaf and curly dock, and common ragweed developed over time. At all sites, the narrow window of management timing in the spring caused cover crops in some treatments to sometimes set seed, which resulted in volunteers in the following cash crop. When cover crops were terminated too early, cover crops regrew, flowered, and sometimes set seed, and when cover crops were terminated too late, cover crops also set seed. Across all sites, early to middle planting dates matched with a cultivar with an appropriate maturity tended to perform best. Corn performance was generally better than soybean at the southern sites (DE and MD) whereas soybean performed better than corn at the northern site (PA); the delayed planting date required in PA to successfully control the hairy vetch cover crop with the roller-crimper greatly reduced corn yield potential.  High-residue cultivation tended to have no impact or reduce crop yields in site-years when weed populations were relatively low, but increased yields when weed populations were high. Based on our results, cover crop-based organic rotational no-till production can be successful if: 1) the site has a low initial weed seedbank, 2) proper equipment is available to ensure cover crop termination and effective cash crop seed-to-soil contact, and 3) the farmer has experience with the system. We believe three years of research at three locations has provided great insight into what can be successful and potentially move forward in no-till organic and what remains challenging, requires additional research, or perhaps is too challenging to be successful in the near future.  Future research should focus on further reducing tillage while maintaining adequate suppression of perennial weeds and examining alternative cover crops and crop rotations that minimize the potential for volunteer cover crops in subsequent cash crops.