Soil physical properties, soil carbon dioxide fluxes, and soil drainage dynamics of select bioenergy cropping systems

Bioenergy cropping systems have been proposed as a way to enhance United States energy security. However, research on soil physical properties, soil-surface CO2 effluxes, and soil drainage dynamics in such systems is needed to ensure environmental sustainability in the field. The objective of our research was to evaluate soil physical properties and conditions as well as soil-surface CO2 effluxes and soil drainage dynamics of selected annualand perennial-based biofuel cropping systems with the goal of comparing these systems for the greatest environmental sustainability in regards to soil and water resources. Near Ames, Iowa, six cropping systems of mixed prairie (nitrogenfertilized and unfertilized), continuous maize with 50 % stover removal (with and without cover crop), and maize-soybean rotation (each crop type grown each year) was initiated with four replications in a randomized complete block design. Soil physical properties evaluating soil structure and water, solute, and gas transfer were evaluated near the soil surface and soil-surface CO2 effluxes, surbsurface drainage quantity and quality, and soil physical conditions were monitored over time. Overall, the environmental sustainability greatly varied among the cropping systems. The removal of corn stover in the early stages after system establishment did not significantly impact soil physical properties, soil-surface CO2 effluxes, or soil water drainage with regards to subsurface drainage flow dynamics or water quality as compared to corn-soybean systems with only grain harvest. However, the incorporation of a winter rye cover crop in continuous corn systems did tend to be more environmentally sustainable as compared to when a cover crop was not used. Though soil physical properties were not improved, spatial variability associated