Evaluating Cover Crops for Weed Reduction throughout the Southern States

During recent research on cover crops in the Lower Rio Grande Valley of Texas, we noticed an anomaly: after a winter planting of crimson clover, pigweed germination was reduced by 95%. Pigweeds (Amaranthus spp) are fast-germinating and fast-growing annual summer weeds found in crop lands throughout the country. We wondered why pigweed was suppressed so greatly by crimson clover. Was it allelopathy or some other factor? Woolly croton, sunflower, and Parthenium were also suppressed to varying degrees by crimson clover, well into the next summer growing season. We have noticed through the years that some cover crops do better than others at controlling specific weeds. For example, in South Texas, pigeon peas suppress sunflowers especially well. And in earlier trials Austrian winter peas showed promise for control of Bermuda grass and nutsedge. These anecdotal findings lead us to wonder if some of these weed suppressing effects can be proven in controlled studies and what other weed/cover crop pairings might be suitable for southern farms. In this research and education project, we worked with limited-resource producers in four southern states, carrying out controlled studies to test the efficacy of various cover crops in suppressing some of the most troublesome weeds. In the process of carrying out these studies, underserved and limited resource farmers in several states gained firsthand experience with cover crops. Producers from the Southeastern African American Organic Network SAFFON), Operation Spring Plant (OSP), and our established collaborators in Texas took inventory of their weeds each season. Based on these inventories, we developed a cover crop selection tool based on cover crop properties and water demands. Knowledge gained from this research and the cover crop selection tool are being disseminated at conferences such as the Texas Organic Farmers and Gardener’s Association (TOFGA) and Southern Cover Crops Council, NCAT’s ATTRA website, partner organization websites, and various social media channels including blogs, Facebook posts and podcasts.

1: Expand the knowledge base concerning which cover crops work best for specific weeds in the South.

2: Expand usage of cover crops by limited-resource producers throughout the South to achieve weed suppression on farm.

3: Develop cover crop selection tools for southern farms.

4: Collect the stories of the farmer cooperators and older farmers about how to deal with weeds in a guide that also includes agronomic data about cover crops so the next generation can benefit from their knowledge.