ARS | Publication request: Carbon and Nitrogen Dynamics in an Eastern Corn Belt Soil: N Source and Rotation

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2008
Publication Date: January 21, 2009
Citation: Hernandez Ramirez, G., Brouder, S.M., Smith, D.R., Van Scoyoc, G.E., Filley, T.R. 2009. Carbon and Nitrogen Dynamics in an Eastern Corn Belt Soil: N Source and Rotation. Soil Science Society of America Journal. 73(1):128-137.

Interpretive Summary: Increasing carbon dioxide concentrations in the atmosphere may be causing global warming effect, which is a very important environmental problem. It is known that agricultural soils can sequester carbon and perhaps reduce carbon dioxide concentrations in the atmosphere depending on the management practices in place. In this study, soil samples were collected in corn and soybean fields as well as in restored prairie grass in Indiana during two years. These soil samples were analyzed for carbon and nitrogen contents. In general, we observed that soil organic carbon was higher due to manure application in the fall. Also, restoration of prairie grass in cropland showed beneficial impact on soil carbon. Corn-soybean rotation was not different than continuous corn in this study. This research is important to growers, scientists, and policy-makers interested in management practices that can enhance the contribution of agricultural soils to both carbon sequestration and global warming mitigation.

Technical Abstract: Soil carbon (C) sequestration may mitigate increasing atmospheric carbon dioxide concentrations, but the relative contribution of diverse management practices is not completely documented. This study was conducted to assess chemical and physical fractions of total organic C (TOC) and total N (TN) as affected by land use, nitrogen (N) fertilizer source, and rotation. Particulate organic matter (POM) and non-hydrolyzable C (NHC) fractions were measured in Drummer and Raub soil series during two growing seasons. Agroecosystems evaluated were continuous corn (CC) and corn grown in rotation with soybean (CS) both with urea-ammonium nitrate (UAN), CC with either spring or fall liquid swine manure (CCSM and CCFM, respectively), soybean in rotation with CSUAN (SC,), and restored prairie grass (PG). In general, CCFM exhibited the largest soil C and N pools likely reflecting temporal coincidence of incorporation of aboveground residue, manure application, and the onset of cold-wet conditions in late fall and/or winter. In corn-soybean rotations, the TOC declined roughly 10% following SC but increased a comparable amount following CSUAN reflecting differences in crop residue C/N ratios. The 2-yr corn-soybean rotation (SC and CSUAN) had a similar overall effect as CCUAN on TOC (ranging from 22 to 24g C kg-1 soil). When compared to CCUAN, PG soils were enriched in TOC, fine POM-C and NHC but not in N pools, which might relate to fine root contribution from PG in these unfertilized fields. Comparison of soil C pools between treatments that differed in TOC revealed that newly sequestered C was preferentially allocated into POM supporting this fraction as an excellent indicator of management effect on C sequestration.