*Article* **Management of High-Residue Cover Crops in a Conservation Tillage Organic Vegetable On-Farm Setting**

#### **Ted S. Kornecki and Andrew J. Price \***

National Soil Dynamics Laboratory, Agricultural Research Service, United States Department of Agriculture, Auburn, AL 36830, USA; ted.kornecki@usda.gov

**\*** Correspondence: price@ars.usda.gov; Tel.: +1-334-887-8596

Received: 16 September 2019; Accepted: 10 October 2019; Published: 15 October 2019

**Abstract:** A three year on-farm conservation-tillage experiment was initiated in fall of 2008 at Randle Farm LLC, located in Auburn, AL. Our objective was to evaluate and demonstrate implementation of tenable conservation vegetable production practices using high amounts of cover crop residues that reduce soil erosion, improve soil productivity and quality, reduce energy costs, and promote farm profitability. Cereal rye, crimson clover, and a rye and crimson clover mixture were evaluated as cover crops; these were terminated using either a prototype two-stage roller/crimper alone or followed by an application of 2.5 L a.i. ha−<sup>1</sup> 45% cinnamon (*Cinnamomum verum* L.) oil (cinnamaldehyde, eugenol, eugenol acetate,)/45% clove oil (eugenol, acetyl eugenol, caryophyllene) mixture in the spring prior to crop establishment. A winter fallow conventional tillage system was included for comparison. Watermelons, cantaloupes, and okra then were transplanted into each cover crop and termination treatment combination in mid-May, utilizing a modified transplanter equipped with a custom fitted subsoiling shank and row cleaners to alleviate soil compaction and facilitate transplanting. In all years, all cover crop treatments exceeded 4000 kg ha−<sup>1</sup> and in 2009 and 2011, exceeded 6000 kg ha−1. At 21 days after termination in 2010 when the slowest termination occurred, higher termination rates were obtained for cereal rye (95% to 96%) followed by lower termination rates for the clover/rye mixture (83% to 85%); the lowest termination rates were obtained for crimson clover (66% to 68%). Commercially available cinnamon/clove oil solution provided little cover crop termination above that provided by a roller crimper alone. Volumetric soil moisture content for rolled/crimped cover crops was consistently higher compared to the conventional system, indicating that flattened and desiccated cover crop residue provided water conservation. In 2010 and 2011, yields for cantaloupe, okra, and watermelons were consistently higher for the conventional system compared with no-till system with cover crops likely due to weed cultivation limitations and insect pressure. Future studies need to focus on weed control and integrated pest management.

**Keywords:** cinnamon oil; clove oil; cover crop termination; organic agriculture; organic herbicides; roller/crimper
