|WILHELM, WALLACE - Former ARS Employee|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2013
Publication Date: 5/6/2013
Publication URL: http://handle.nal.usda.gov/10113/56456
Citation: Wienhold, B.J., Varvel, G.E., Johnson, J.M., Wilhelm, W.W. 2013. Carbon source quality and placement effects on soil organic carbon status. BioEnergy Research. 6:786-796. Available: http://link.springer.com/content/pdf/10.1007%2Fs12155-013-9301-z.pdf.
Interpretive Summary: Soils have the potential to store significant amounts of organic matter and increasing this process can reduce the buildup of atmospheric carbon dioxide. Management practices that increase accumulation of organic matter need to be developed. This study compared soil organic matter changes in soils growing plants and protected from raindrop impact and soils receiving carbon sources that varied in the rate they could be utilized by soil biota. Soil organic matter increased in soils where plants were grown and the surface received protection from raindrops. Soils receiving readily utilized carbon sources had poorer soil structure and lower amounts of components of soil organic matter. Management practices that protect the soil and promote improved soil structure accrue soil organic matter.
Technical Abstract: Improved management of agricultural soils has potential for sequestering carbon (C) and reducing the accumulation of atmospheric carbon dioxide. Development of management practices to increase C sequestration is dependent on improved understanding of soil processes influencing long-term storage of C. A field study was conducted to compare surface C source quality and above- vs. below-ground addition of annual or perennial plant biomass effects on particulate organic matter (POM), total labile C (TLC), and total organic C (TOC). Since microaggregate stabilization within macroaggregates is the main mechanism for sequestering C, aggregate size distribution, expressed as mean weight diameter (MWD), and wet aggregate stability (WAS) was also measured. After 5 years POM decreased in plots receiving surface application of readily available substrate (sucrose and alfalfa pellets) and the bare surface control. Plots receiving plant additions (wood chips, growing wheat crop, growing switchgrass crop and fallow receiving either wheat or switchgrass residue) exhibited higher TLC and TOC content. Plots receiving plant residue maintained MWD and those supporting live plants exhibited increasing WAS. Surface plant residue protected the soil against raindrop impact and reduced the intensity of wetting and drying cycles allowing the development of larger more stable aggregates resulting in C accrual.