COMPARISON OF SUBSTRATE UTILIZATION ASSAY AND FATTY-ACID ANALYSIS OF SOIL MICROBIAL COMMUNITIES

Two methods for the characterization of microbial communities in field soil samples were compared. Experimental subplots were established in the Farming Systems Trial at the Rodale Institute Research Center in Kutztown, PA, USA. In the legume system, plots receiving green manure (hairy vetch) were compared to those receiving corn stover and a small amount of rye residue. In the conventional system, samples were colle cted in plots where corn stover was incorporated. Carbon source utiliz ation profiles were developed using Biolog plates, while total soil fa tty acids were determined by fatty acid methyl ester analysis. Princip al component analysis and canonical discriminate analysis were used to analyze the data. The two methods gave similar but not identical resu lts. Management history had more effect than specific crop residue, bu t temporal effects were greater than treatment effects. Certain shifts in microbial communities were detected by fatty acid analysis but not by carbon utilization assay, suggesting that changes in microbial spe cies composition occurred that were not accompanied by changes in micr obial community function. (C) 1997 Elsevier Science B.V.