The critical period of cover crop management: A framework for maximizing biomass potential and minimizing volunteers with buckwheat

Buckwheat (Fagopyrum esculentum Moench) is a short-duration high-biomass cover crop often grown in potato (Solanum tuberosum) rotations to provide select agroecosystem services. However, buckwheat's short generation time challenges its continued viability as a cover crop as seed is rapidly produced, resulting in volunteer issues in subsequent crops with limited control options. Field studies were conducted in Atlantic Canada over two seasons to model buckwheat biomass production and viable seed yield as a function of planting and termination time with the goal of providing a framework to maximize biomass production while minimizing seed return, termed the critical period of cover crop management. The model demonstrated that maximum buckwheat total (979 g m⁻²) and vegetative (565 g m⁻²) biomass production could be attained when planted by 2 and 3 growing degree days base 5 (GDD₅) accumulation and grown for 1680 and 2110 GDD₅, respectively. Viable seed production rapidly increased with earlier planting dates and later termination dates up to a maximum of 3653 and 5974 seeds m⁻², respectively. Viable seed production could be minimized to 25% of the total if terminated by 696 GDD₅ or sown after 861 GDD₅ had accumulated. Values below this threshold could not be modeled in the termination study. Overall, our results provide a framework for producers to time cover crop planting and termination time to maximize the provision of agroecosystem services while minimizing the return of viable seed to their cropping systems.