Optimizing organic no-till planted soybean with cover crop selection and termination timing

Authors: LIEBERT, JEFFREY - Cornell University; Mirsky, Steven; PELZER, CHRIS - Cornell University; RYAN, MATTHEW - Cornell University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2023
Publication Date: 6/20/2023
Citation: Liebert, J., Mirsky, S.B., Pelzer, C.J., Ryan, M.R. 2023. Optimizing organic no-till planted soybean with cover crop selection and termination timing. Agronomy Journal. 115:1938-1956. https://doi.org/10.1002/agj2.21390.
DOI: https://doi.org/10.1002/agj2.21390

Interpretive Summary: Cereal cover crops are good for weed suppression. Cereal rye is the dominant cover crop used in organic soybean production in the US and considered the best for weed suppression. Less is known about the cover crop triticale regarding its ability to suppress weeds and its impact on a soybean cash crop. Therefore, we investigated the effect of cover crop cultivar and termination timing on cover crop growth, weed biomass, and soybean yield in organically managed no-till soybean. We found earlier cover crop termination dates to result in greater soybean yield and have just as sufficient weed suppression as later termination dates. While cereal rye is the traditional first choice for a winter grass cover crop, we found triticale to perform just as well, adding to farmer options. This information will be useful for farmers using cereal cover crops for weed suppression.

Technical Abstract: Agroecosystem redesign is an important step towards transformative change in the agri-food system, whereby farmers ecologically reshape their operations using agroecological practices; however, support for such knowledge-intensive management is lacking. We conducted a field experiment in Maryland and New York to assess the effect of cover crop cultivar selection and cover crop termination-soybean [Glycine max (L.) Merr.] planting (roll-plant) date on cover crop growth stage, biomass, and reseeding; weed biomass; and soybean density and yield in organically managed no-till planted soybean production. Twelve winter cereal cultivars—four each for barley (Hordeum vulgare L.), cereal rye (Secale cereale L.), and triticale (× Triticosecale Wittm. ex A. Camus.)—were seeded at equivalent rates and terminated at four roll- plant dates. Although many cover crop cultivars had not yet reached the recommended growth stage for adequate termination (anthesis, Zadoks 60) at the earlier roll-plant dates, we observed greater soybean yields than at later dates and similar cover crop reseeding. Weed biomass was low across treatments despite cover crop biomass production below the recommended threshold of 8 Mg ha-1, suggesting this threshold should be reevaluated for greater context-specificity. The effect of cultivar was often inconsistent, but differences among species indicated that triticale performed as well as cereal rye in terms of biomass production, weed suppression, and soybean yield. Our results show that triticale is a viable option for these cover crop-based systems, which provides farmers with another option for diversifying their operations.