Fig. 3 Concentration of SOM present as total amino sugars (A) and glucosamine (B) as related to the TOC content in conventional () and no-tillage soils () at Mandan, ND, Stratton, CO, Bushland, TX, Sidney, NE, Manhattan, KS, and Lexington, KY. Mean values with standard errors are shown, n = 3. Pairs of bars with the same letter signify no sigificant difference at P < 0.05 between the two cropping systems