Use of growing degree days to model the dynamics of aboveground biomass and nitrogen accumulation of winter cover crops

Abstract Cover cropping is an important management practice that can benefit the cash crop and the environment. Plant species, weather, and cover crop termination influence biomass production and N fixation potential. This study was conducted to determine optimal termination dates for production systems in Arkansas based on growing degree days (GDD) for eight different cover crop species: Austrian winter pea (AWP) ( Pisum sativum ), balansa clover ( Trifolium michelianum ), barley ( Hordeum vulgare ), black‐seeded oats ( Avena sativa ), common vetch ( Vicia sativa var. Cahaba), cereal rye ( Secale cereale ), crimson clover ( Trifolium incarnatum ), and hairy vetch ( Vicia villosa ). Field studies were conducted at three research stations in Arkansas to provide differences in climate and rate of GDD accumulation. An area of 0.17 m 2 was harvested for aboveground biomass and total N uptake randomly within each experimental unit every 2 weeks, starting on February 15. Aboveground biomass accumulation and N content were regressed as a function of GDD for each cover crop treatment. At the Rohwer site, AWP, for example, accumulated an average of 3643 kg ha −1 of biomass and 107 kg N ha −1 at termination, whereas 30 days before termination, the average was 1868 kg ha −1 of biomass and 69 kg N ha −1 . The growth rate increased dramatically closer to termination due to warmer temperatures, which allowed for rapid GDD and aboveground biomass accumulation. These results suggest that termination dates can be identified using previous and forecasted weather data.