Bioenergy Production and Carbon Sequestration Dynamics Under Conservation Reserve Program Management System.

The conservation reserve program (CRP) is the largest public-private partnership initiative in the United States for incentivizing land owners to physically retire their environmentally sensitive land from intensive production. The CRP goals include restoring land quality, improving air and water quality and building wildlife habitat. Currently, CRP lands planted with warm-season perennial grass mixes (i.e. C₄ species) are not harvested for bioenergy use. The objective of this study was to assess the potential of CRP lands to provide biofeedstock for bioenergy production without compromising the intended goals. It was hypothesized that harvesting aboveground biomass as bioenergy feedstock could improve soil quality. Soil cover measurements on land that was first introduced into the CRP program in 1999 was conducted after ten years of establishment starting in 2009 through 2011.

In 2009, an experiment was initiated on the same CRP site (i.e. located in The Ohio State University, South Centers, Piketon OH; N: 39° 02.855-39° 02.873; W: 82° 59.261-82° 59.355; Elevation: 176 meter) that included four replications of five levels of N (N1-0, N2-10, N3-20, N4-40, and N5-80 kg N ha^-1) and three management strategies (A, for single dry harvest in the winter during March-April; B, for double harvest at the green stage in May and then again at the dry stage in winter during March-April, and C, for multiple green harvests in May through October-November). A detailed soil sampling was performed in 2009 and then again in 2014 and aboveground biomass sampling was done annually from 2009 through 2014.

Results showed that land cover declined from 1999 to 2009 by 40% but then, averaged across all treatments, recovered to 100% in 2011. Nitrogen application that began in 2009 was not a contributing factor in improving the overall soil quality between 2009 and 2014. Starting in 2009 and comparing to 2014, above ground biomass production was increased from ~5.0 to 17.0 Mg ha^-1 yr^-1 with Management-A; from 4.0 to 12.0 Mg ha^-1 yr^-1 with Management-B; and from 4.0 to 11.0 Mg ha^-1 yr^-1 with Management-C. Likewise, energy yield (GJ ha^-1 yr^-1) correspondingly increased from 96.0 to 287.0 with Management–A, 83.0 to 202 with Management–B, and 83.0 to 194 with Management–C. Averaged across all management strategies, soil carbon sequestration in the top 1 meter of soil significantly increased by 25% from 32.0 to 40.0 Mg ha^-1 in six years period (2009-2014). In conclusion, management strategies and time of biomass harvest contributed significantly to the overall changes in soil properties, including improvement of those properties related to soil quality.