Aboveground productivity and soil carbon storage of biofuel crops in Ohio.

Biofuel crops may help achieve the goals of energy-efficient renewable ethanol production and greenhouse gas ( GHG) mitigation through carbon (C) storage. The objective of this study was to compare the aboveground biomass yields and soil organic C ( SOC) stocks under four crops (no-till corn, switchgrass, indiangrass, and willow) 7 years since establishment at three sites in Ohio to determine if high-yielding biofuel crops are also capable of high levels of C storage. Corn grain had the highest potential ethanol yields, with an average of more than 4100 L ha−1, and ethanol yields increased if both corn grain and stover were converted to biofuel, while willow had the lowest yields. The SOC concentration in soils under biofuels was generally unaffected by crop type; at one site, soil in the top 10 cm under willow contained nearly 13 Mg C ha−1 more SOC (or 29% more) than did soils under switchgrass or corn. Crop type affected SOC content of macroaggregates in the top 10 cm of soil, where macroaggregates in soil under corn had lower C, N and C : N ratios than those under perennial grasses or trees. Overall, the results suggest that no-till corn is capable of high ethanol yields and equivalent SOC stocks to 40 cm depth. Long-term monitoring and measurement of SOC stocks at depth are required to determine whether this trend remains. In addition, ecological, energy, and GHG assessments should be made to estimate the C footprint of each feedstock. [ABSTRACT FROM AUTHOR]