Evaluation of Organic Spring Cover Crop Termination Practices to Enhance Rolling/Crimping.

With organic farming hecterage and cover crop interest increasing throughout the United States (U.S.), effectively timed cover crop termination practices are needed that can be utilized throughout the growing season. A two-year cover crop termination experiment was established in Alabama in fall, 2013. Four commercially available termination treatments were evaluated immediately following mechanical termination with a cover crop roller/crimper: 1) 20% vinegar solution, 2) 2.84 L/ha 45% clove oil/45% cinnamon oil mixture, 3) solarization using 0.15mm clear polyethylene sheeting with edges manually tucked into soil for 28 days over the entire plot, and 4) broadcast flaming emitting 1,100°C (approximately 7.3 million kj) applied at 1.2 km/h. A rolled/crimped alone treatment, and the synthetic herbicide glyphosate applied at 1.12 kg/ae ha, were included for comparison. Five cover crop species were evaluated: 1) hairy vetch, 2) crimson clover, 3) cereal rye), 4) Austrian winter peas, and 5) rape. Three termination timings occurred at four week intervals beginning mid-March each year. Clove/cinnamon oil and vinegar were generally non-effective at termination over rolling/crimping alone in either year. In March, rye and rape was not terminated by any practice, while solarization was effective in April. By May, rolling/crimping alone terminated vetch 90%, peas 96%, and clover, rye 99%. Solarization was effective in March for vetch termination (95%) while solarization provided 72% termination of clover and 93% pea termination. In 2014 due to warmer winter and spring temperatures, similar termination results were observed for March 2014 as were observed in April 2013. Clove/cinnamon oil was the least expensive and one of the least effective termination methods. Vinegar, along with clear plastic, had the highest costs driven by product costs and application rates; however, in general, it was not an effective termination method. While expensive, clear plastic was an effective termination method, however this practice requires additional labor and machinery time as compared to other treatments. The cost of flame termination was almost four times the cost of the glyphosate treatment; however, it proved to be an effective termination option for most covers evaluated. Organic producers needing to terminate winter covers would most likely be successful using a broadcast flamer for most winter covers or utilizing clear plastic for hairy vetch, winter peas, or cereal rye as ambient temperature increases along with solar radiation, both in combination with a roller/crimper. Commercially available vinegar and clove/cinnamon oil solutions provided little predictable termination and producers are likely to resort to tillage if no other material or practice is readily available.