The Legacy Matters: Cover Crop Management in Organic Rotational No-till.

Organic rotational no-till has many potential benefits including lower fuel costs and increased soil quality by reducing tillage in organic systems.  Research on organic rotational no-till practices has been limited to investigating single phases of crop rotations.  The Reduced-tillage Organic Systems Experiment (ROSE) evaluated cover crop performance through a three-year crop rotation at sites in Delaware, Maryland, and Pennsylvania from 2011-2013.  The corn-soybean-wheat rotation had a hairy vetch-triticale cover crop preceding corn and cereal rye preceding soybean.  Rotational no-till was accomplished by terminating cover crops with a roller-crimper and no-till planting cash crops into the mulch.  Moldboard plowing occurred after cash crop harvest to incorporate residues and prepare a seedbed for the following crop.  Three termination timings (Early, Middle, and Late) were tested to determine the effects of delayed termination on cover crop biomass accumulation and effective kill.  Hairy vetch-triticale biomass increased with delayed termination in 5 of 9 site-years and control generally improved as termination was delayed.  Hairy vetch-triticale biomass was maximized at approximately 50% vetch flowering but if termination was delayed until 100% flowering or early pod set volunteer vetch in subsequent crops was generally reduced.  Volunteer hairy vetch was the most significant weed in the following rye cover crop reaching 305, 1,180, and 41 kg ha^-1 at Delaware, Maryland, and Pennsylvania, respectively.  In 2013, volunteer vetch in the wheat reached a maximum of 3,460 kg ha^-1 at Maryland and significantly decreased wheat grain yield.  Cereal rye biomass increased with delayed termination in 8 of 9 site years and control consistently exceeded 85%.  Despite good control and regrowth below 100 kg ha^-1, volunteer rye was a problem in wheat at Pennsylvania: in 2013 volunteer rye contamination of wheat grain averaged 215 kg ha^-1.  ROSE demonstrated that consistent cover crop biomass production is achievable and that volunteer cover crops may compromise system performance.