Cover crop residue retention on the soil surface can suppress weeds and improve organic no-till soybean (Glycine max) yield and profitability compared to a tilled system. Appropriate cereal rye (Secale cereale) fall planting date and termination methods in the spring are critical to achieve these benefits. A plot-scale agronomic experiment was carried out from September 2018 to October 2021 in Kutztown, PA, USA to demonstrate the influence of cereal rye planting date (September or October) and mechanical termination method [no-till (I & J roller-crimper, Dawn ZRX roller, and mow-ted) and tilled (plow-cultivate)] on cover crop regrowth density, weed biomass, soybean yield, and economic returns. In one out of three years, the September rye planting accumulated more cover crop biomass than the October planting, but the regrowth of the rye after roller-crimping was greater with this planting date. Cover crop planting date had no effect on total weed biomass and demonstrated varying effects on soybean grain yield and economic returns. The Dawn ZRX roller outperformed the I & J roller-crimper in effectively terminating cover crops, while the I & J roller-crimper demonstrated more uniform weed suppression and led to greater soybean yields over a span of three years. Organic no-till strategies eliminated the need for tillage and reduced variable costs by 14% over plow-cultivated plots, and generated ~19% greater net revenue across the study period (no-till vs tillage = US $845 vs US $711 ha−1). Terminating cereal rye with roller-crimping technology can be a positive investment in an organic soybean production system.

Several approaches can be used to terminate legume cover crops in the spring prior to planting summer crops, but the effect that these methods have on decomposition and nitrogen (N) release dynamics of legume cover-crop roots is poorly understood. The main objectives of this study were to: (i) quantify decomposition and N release of roots from pea (Pisum sativum), clover (Trifolium incarnatum) and vetch (Vicia villosa Roth); (ii) determine if roots decompose and release N faster when cover crops are terminated by disking compared with roller-crimping; and (iii) determine if roots decompose and release N faster under higher soil inorganic N levels. Two field experiments were conducted in Goldsboro and Kinston, North Carolina in the summer of 2012. Cover crops at these sites were terminated in spring by disking or roller-crimping and planted to unirrigated corn. Air-dried roots placed in litterbags were buried in their corresponding cover-crop plots and in plots where cover crops had not been grown that had either synthetic N fertilizer added at burial or had no fertilizer addition. Root litterbags were collected over 16 weeks at both sites. Cover-crop plots terminated by disking had up to 117 and 49% higher soil inorganic N than roller-crimped plots in Goldsboro and Kinston, respectively. However, roots did not appear to contribute significantly to these increases, as measured root decomposition and N release was not affected by termination approach at either site. Roots decomposed rapidly at both sites, losing up to 65% of their original biomass within 4 weeks after burial. Root N release was also rapid at both sites, with vetch generally releasing N fastest and clover slowest. It was estimated that cover-crop roots supplied 47–62 and 19–33 kg N ha−1 during the corn cycle in Goldsboro and Kinston, respectively. Our results indicate that under the warm, humid summer conditions of the Southeastern USA, legume cover-crop roots decompose and release N rapidly.