Rye planting date impacts biomass production more than seeding rate and nitrogen fertilizer

Management is critical to maximize cover crop benefits, while minimizing costs. However, cover crop performance and cost can vary without consistent management strategies. Therefore, we investigated how four planting dates (late October, early November, late November, and early December), two seeding rates (67 and 101 kg ha(-1)), and four N rates (0, 34, 67, and 101 kg N ha(-1)) affected rye (Secale cereale L., 'Wrens Abruzzi') biomass production, N uptake, C:N ratio, $ per 100 kg biomass, cash crop yields, and soil organic C (SOC) in a peanut (Arachis hypogaea L.)/cotton (Gossypium hirsutum L.) rotation over six growing seasons (2015-2020) in Headland, Alabama, USA. Biomass production averaged 170% greater for late October planted rye compared to early December across all N rates. Nitrogen increased biomass production, but total biomass amounts decreased with later planting dates. Nitrogen uptake increased as N rate increased for each planting date. The C:N ratio was more sensitive to planting dates than N rates and decreased as planting was delayed. The $ per 100 kg of biomass was similar across all N rates for early planting dates (late October and early November). No yield effect was observed for peanut or cotton, but SOC increased in the 0-5 cm depth when 101 kg N ha(-1) was applied to the rye cover crop. Results highlight the importance of planting date compared to seeding and N rates to enhance cover crop performance and return on investment (ROI) for growers in the southeastern United States.