Characterization of Organic Carbon in Soil Aggregates from Temperate Continuous Corn System with Contrasting Management Practices Using Nexafs and 13C-NMR Spectroscopy.

Understanding the chemistry of soil organic carbon (SOC) is useful in determining the level of C stabilization in different agroecosystems. Synchrotron based C (1s) near edge X-ray absorption fine structure spectroscopy (NEXAFS) is useful in recognizing and fingerprinting SOC as well as in investigating the effects of contrasting management practices on composition and biogeochemical cycling of C at molecular level.

Soil samples were collected from north agronomy farm, Manhattan, Kansas, USA (39º 12’ 42” N, 96º 35’ 39” W) from 0-5 cm depth.  This site was under 22 years of continuous corn and had two tillage treatments (tilled and no-tilled), two fertilizer treatments to supply 168 kg N ha^-1 (High manure/compost and high fertilizer/ ammonium nitrate) and a control (4 filed replicates per treatment combinations).  Four water stable aggregate sizes (> 2 mm, 2-0.25 mm, 0.25-0.053 mm and < 0.053 mm) were separated by wet sieving and composite soil samples were used for bulk NEXAFS studies.

Bulk C (1s) NEXAFS of composite soil samples were collected at the spherical grating monochromator (SGM) beamline (11ID-1 endstation) at Canadian light source, Saskatoon. Data analysis will be done using Igro Pro and Athena.

Outcome of this study will provide useful information on SOC entrapped in soil aggregates led to the differences in their resilience.  In addition, these results will be a great addition to the bigger picture in recognizing the management practices with greater potential of soil C sequestration which will be useful in suggesting mitigation options for greenhouse gas offsets.