Fig. 1 Ratios of glucosamine to muramic acid for the 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