Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/19/1998
Publication Date: N/A
Technical Abstract: Soil samples from a long-term experiment on tillage, residue and nitrogen management under continuous corn from selected years were analyzed for C and **13C. Carbon contents in tilled plots decreased slightly with years of cropping. Amounts of C in no-till plots with residues removed remained about the same with years of cropping, while those with residues returned increased markedly. The delta**13C values increased steadily with years of cropping in all treatments; the no-till with residues returned having the highest increase. Nitrogen effects on C and **13C seemed to be evident only with no-till plots with residues returned. The delta**13C values increased with depth in both tilled and no-till plots. In the 15- to 30-cm depths, carbon contents decreased and delta**13C values increased with years of cropping under no-till, especially with residues removed. There was no consistent trend in C contents and delta**13C values in the 15- to 30-cm depths in tilled plots with years of cropping.