Found an abstract which might explain how excess N messes with soil carbon sequestration:
“The added NO3- suppressed mineralization of C from SOM and stimulated mineralization of C from stover. Adjustment of rates of stover decomposition to temperature regimes normally encountered in Iowa fields after harvest showed that stover decomposition would not be complete within 1 yr and that increases in NO3- availability decreased the amount of stover C remaining in the soil. This effect of NO3- could explain how additions of unneeded N could decrease concentrations of SOM in long-term studies in which residues and NO3- are added in annual cycles. These observations suggest that practices that reduce unnecessary fertilization could help conserve SOM and reduce net amounts of CO2 released to the atmosphere.”
Next: My pathetic attempt to translate this into understandable terms after reading the whole study, if I can get my hands on it.
Update: No luck finding the full study after searching two state university library systems. Here’s the citation for this article in case anyone’s interested:
Title: NITROGEN EFFECTS ON CONSERVATION OF CARBON DURING CORN RESIDUE DECOMPOSITION IN SOIL
Author(s): GREEN CJ, BLACKMER AM, HORTON R
Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL 59 (2): 453-459 MAR-APR 1995
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