Cover Crop Termination Timing is Critical in Organic Rotational No‐Till Systems

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Core Ideas Hairy vetch–triticale biomass peaked at early hairy vetch flowering but mechanical control was highest at late flowering to early pod set. Cereal rye biomass peaked at late dough stage but optimal mechanical control was obtained between 50% anthesis and early milk stages. Volunteer hairy vetch was problematic in Delaware and Maryland whereas volunteer cereal rye was problematic in Pennsylvania. Volunteer cover crops resulting from incomplete termination with mechanical rolling can be problematic in subsequent crops and may impact the benefits of organic rotational no‐till. 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 resulting mulch. A systems experiment was conducted at three Mid‐Atlantic locations to test how cover crop termination timing affects cover crop biomass production, control, and volunteers in subsequent crops during the transition to organic production. The annual crop rotation was hairy vetch (Vicia villosa Roth) plus triticale (x Triticosecale Wittm.)–corn (Zea mays L.)–cereal rye (Secale cereale 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 in all site‐ 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.