Quantification of Ecosystem Services from Temporal Intensification of Crop Production Across a Longitudinal Gradient.

Land resources are becoming progressively more constrained with increasing demands for food, feed, fiber, and now fuel production. Developing strategies to intensify crop production without increasing the negative impacts on water, soil, and air resources are critical. Much of the best agricultural lands are dominated by corn-soybean rotations with winter fallow periods. There has been interest in spatially diversifying and temporally intensifying production of the farm landscape to improve water quality. Winter cover crops are one strategy to reduce nutrient losses over winter, but they have not been widely adopted. Harvested cover crops, or double crops, of winter small grains are common in some regions. Our objective was to quantify the value of ecosystem services along with crop residues as a cellulosic bioenergy feedstock from winter double crops, to assess their potential as incentives for deployment into the landscape. The biogeochemical model DayCent was used to quantify the impact of winter double crops on nitrate leaching, nitrous oxide emissions, and soil carbon. We then evaluated a range of values for these ecosystem services, along with biomass, as potential economic incentives to increase the economic returns for planting these crops. Reduction in nitrate leaching was the highest valued ecosystem service provided by the winter double crops, then soil carbon and N₂O emissions. Although rye provided significant yield and ecosystem services, it was never economic and was the most expensive winter double crop. However we found that in addition to significant value from ecosystem services with planting winter small grains, they also had lower breakeven prices and yields leading to greater potential as a cellulosic bioenergy feedstock. Considering the sensitivity of double crop rotation economics to soybean yields, and that barley has less impact on soybean yields than wheat north of the 40^th parallel, establishment of a bioenergy market for biomass could provide significant incentive for wide spread planting of winter barley as a double crop in corn-soybean rotations, and realize significant environmental benefits.