IMPACTS OF CROP RESIDUE REMOVAL FOR BIOFUEL ON SOILS

Project: Research project

Project Details

Description

The link between rising atmospheric CO2 concentrations and global climate change makes it increasingly important that we find ways to minimize soil CO2 emissions and sequester carbon (C) in terrestrial ecosystems. Because soils contain the largest near surface reservoir of terrestrial C, and much of this C has been lost during agricultural conversion (Schlesinger 1997), soils have a high potential for C sequestration (USDOE 2011; Lemus & Lal 2005). Highly productive bioenergy cropping systems represent one possible way to increase soil C sequestration that have the added benefit of reducing C emissions associated with fossil fuel consumption (Liebig et al. 2005; Lemus & Lal 2005; Hansen et al., 2004). However, biofuel crops likely vary in their capacity to enhance soil C sequestration. Corn, for example, is currently the most common biofuel crop but its capacity to sequester C is much lower than that of perennial grasses such as switchgrass (Panicum virgatum), miscanthus (Miscanthus spp.) and native prairie grasses such as big blue stem (Andropogon gerardii; Liebig et al. 2005; Zan et al. 2001). Perennial grasses have been observed to enhance soil C stocks within several years when cultivated in degraded soils, or in comparison to conventional agricultural systems like corn (Haney et al. 2010; Liebig et al. 2005; Hansen et al. 2004; Zan et al. 2001; Potter et al. 1999). While we know that perennial grasses can increase soil C concentrations, the mechanisms underlying these increases are not known. What we do know is that reported increases in soil C stocks must originate primarily from belowground inputs because most aboveground material is harvested in biofuel systems. Indeed, perennial grasses may have a higher potential for C sequestration than corn because the root:shoot ratios of these grasses are much higher (e.g. switchgrass 1.5 versus corn 0.2), so their below ground contributions from both dead roots and root exudates are greater (Liebig et al. 2005; Hansen et al. 2004). In addition to producing greater root biomass, perennial grass roots typically go deeper than corn roots, which likely explains some of the reported increases in deep soil C in biofuel cropping systems (>30 cm; Liebig et al. 2005; Hansen et al. 2004; Zan et al. 2001). While it seems clear that under some conditions perennial grass bioenergy cropping systems can increase soil C stocks, and that this is likely due to high levels of below-ground productivity, the mechanisms of formation, stability and longevity of root-derived soil C are poorly understood. The goal of this research is to examine the cycling and stabilization of root-derived C under different perennial biofuel cropping systems.

StatusFinished
Effective start/end date10/1/109/30/19

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