Winter Rye Cover Crop Seeding Rate and Termination Timing Effects on Cover Crop Biomass and Quality

Winter rye (Secale cereale L.) biomass and chemical composition influences decomposition rates, nutrient cycling and effects on cash crop growth. Management that maintains rye biomass while lowering carbon (C) to nitrogen (N) ratios and concentrations of structural carbohydrates including hemicellulose, cellulose, and lignin could maintain some ecosystem services while accelerating nutrient cycling. Two independent studies examined (1) five rye seeding rates ranging from 0 to 90 kg ha(-1) and (2) five termination dates ranging from April 19 to May 31 (585 to 1084 growing degree days) to understand management induced relationships between rye biomass, nutrient concentrations, and composition of hemicellulose, cellulose, and lignin. Rye biomass increased at seeding rates of 90 kg ha(-1) as compared to the 22-67 kg ha(-1) seeding rates while trends toward higher plant structural components were observed as seeding rate increased. Rye biomass accumulated rapidly beyond 819 (May 13) growing degree days while increasing rye C:N ratio and concentrations of hemicellulose and cellulose. Rye C:N ratio was strongly correlated to rye biomass (R-2 = 0.80, p < .001) with a C:N ratio of 25 associated with 2000 kg ha(-1) of rye biomass. Changes in rye residue quality were strongly influenced by biomass accumulation with delaying termination most significantly driving biomass changes. Trends toward lower C:N ratios and concentrations of structural carbohydrates were seen at the 22-67 kg ha(-1) seeding rates even without differences in biomass suggesting lower seeding rates could cycle nutrients quicker without limiting biomass production potential.

Automated summary

Winter rye biomass and composition, including carbon:nitrogen ratios and concentrations of structural carbohydrates, have significant impacts on decomposition rates, nutrient cycling, and cash crop growth. Higher seeding rates and delayed termination dates can increase rye biomass and nutrient concentrations, but also result in higher C:N ratios and concentrations of hemicellulose and cellulose. Lower seeding rates can potentially cycle nutrients faster without limiting biomass production potential.