Cover crop termination timing is critical in organic rotational no-till systems

Authors: KEENE, CLAIRE - Pennsylvania State University; CURRAN, WILLIAM - Pennsylvania State University; WALLACE, JOHN - Pennsylvania State University; Mirsky, Steven; RYAN, MATTHEW - Cornell University; VANGESSEL, MARK - University Of Delaware; BARBERCHECK, MARY - Pennsylvania State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2016
Publication Date: 1/25/2017
Citation: Geene, C., Curran, W.S., Wallace, J., Mirsky, S.B., Ryan, M.R., VanGessel, M., Barbercheck, M. 2017. Cover crop termination timing is critical in organic rotational no-till systems. Agronomy Journal. 109:272-282.

Interpretive Summary: Rolled down cover crops can provide a surface mulch for organic farmers to no-till plant their corn and soybean cash crops into. The cover crop is the essential component of the system since without tillage, organic growers are limited on weed control options. Previous research has evaluated the performance of the cover crop for suppressing weeds under various production conditions. However, this work was not done within a long-term cropping systems experiment which is required for testing how well cover crops can be integrated into a crop rotation and any unforeseen complications. Therefore, a cropping system experiment was conducted at three locations in the Mid-Atlantic to test how timing of cover crop termination effects cover crop biomass production, control, and contamination in subsequent crops during the transition to organic production. The crop rotation was hairy vetch plus triticale-corn-cereal rye-soybean-winter wheat using a full-entry design. Cover crops were terminated based on growth stages designated Early, Intermediate, or Late. Hairy vetch-triticale and cereal rye biomass production exceeded 5000 kg ha-1 by Late termination at all sites in all years. Although hairy vetch-triticale biomass production peaked at early flowering of hairy vetch, control increased as termination was delayed. Hairy vetch regrowth and volunteer hairy vetch in subsequent soybean and winter wheat crops was lower in Late compared to Early termination treatments. Cereal rye biomass increased as termination was delayed but optimal control was achieved with Intermediate termination. Rolling cereal rye Early resulted in tillering and seed production whereas rolling Late allowed kernels to mature. Wheat grain contamination by volunteer hairy vetch ranged from 11 to 29% and by volunteer cereal rye from 3 to 11% at Maryland and Pennsylvania, respectively, demonstrating that minimizing cover crop seed production with strategic termination is critical for the success of organic rotational no-tll crop production. With current grain shortages in the US for organic animal industry, developing strategies that scale up production and increase adoption is critical. Reducing tillage in organic grain production is one mechanism to achieve that goal. This work helps inform producers on the challenges to managing cover crops in such systems and will aid them in reducing tillage in their production systems.

Technical Abstract: Cover crop-based rotational no-till enables organic farmers to reduce labor and build soil health. In these systems, cover crops are terminated with a roller-crimper and cash crops are direct-seeded into the mulch. A cropping system experiment was conducted at three locations in the Mid-Atlantic to test how timing of cover crop termination effects cover crop biomass production, control, and contamination in subsequent crops during the transition to organic production. The crop rotation was hairy vetch (Vicia villosa Roth) plus triticale (x Triticosecale Wittm.)-corn (Zea mays L.)-cereal rye (Secale cereal L.)-soybean [(Glycine max (L.) Merr.]-winter wheat (Triticum aestivum L.) using a full-entry design. Cover crops were terminated based on growth stages designated Early, Intermediate, or Late. Hairy vetch-triticale and cereal rye biomass production exceeded 5000 kg ha-1 by Late termination at all sites in all years. Although hairy vetch-triticale biomass production peaked at early flowering of hairy vetch, control increased as termination was delayed. Hairy vetch regrowth and volunteer hairy vetch in subsequent soybean and winter wheat crops was lower in Late compared to Early termination treatments. Cereal rye biomass increased as termination was delayed but optimal control was achieved with Intermediate termination. Rolling cereal rye Early resulted in tillering and seed production whereas rolling Late allowed kernels to mature. Wheat grain contamination by volunteer hairy vetch ranged from 11 to 29% and by volunteer cereal rye from 3 to 11% at Maryland and Pennsylvania, respectively, demonstrating that minimizing cover crop seed production with strategic termination is critical in rotational no-till.