A Conceptual Framework for Evaluating Multifunctionality of Cover Crops In Agroecosystems.

Developing agroecosystems that provide multiple ecosystem functions is gaining interest due to rising costs of agricultural inputs and concerns about the environmental impacts of farming. It can be challenging, however, to manage for multiple functions simultaneously due to tradeoffs between functions and the lack of a framework for understanding these dynamic interactions. Cover crops provide an opportunity to improve multifunctionality by increasing the temporal and functional diversity of cropping systems.  We developed a conceptual framework for analyzing the temporal dynamics of multiple ecosystem functions in temperate grain crop systems to understand the potential effects of cover crops.  We synthesized published literature and quantitative models to diagram the seasonal dynamics of twelve functions provided by a low-input, wheat-corn-soybean rotation in the Mid-Atlantic U.S.  The functions broadly represent biomass production, nitrogen cycling, weed suppression, insect regulation, soil quality, and management risk.  We compared this base crop rotation to the same rotation with cover crops (red clover frost-seeded into the winter wheat and cereal rye planted between corn and soybean crops) and estimated the influence of cropping system on yield and the relative risk of yield reductions due to management constraints.  We analyzed multifunctional potential by plotting normalized function scores on radar plots at key time points and integrated across the three-year rotation. Cover crops increased overall multifunctionality compared to the system without cover crops.  The greatest increases in multifunctionality occurred during spring when overwintering cover crops extended the growing season at a time with high potential for biological activity, biomass production, and nutrient and soil loss.  Spring is also a time of greatest management urgency and we found tradeoffs between several ecosystem functions provided by the cover crop and management risk for the subsequent cash crop.  Our framework provides insights into temporal gaps in function provisioning within a typical grain crop rotation and opportunities and challenges to filling these gaps through the use of cover crops.