Impact of Long-Term Tillage and Crop Rotations on Soil Microbial Communities.

Fatty acid methyl esters analysis (FAME) was used to assess differences in soil microbial community structure in four long-term management systems. Sixteen composited soil samples from four treatments of no tillage (NT) vs. conventional tillage (CT) and continuous wheat (CW) vs. a wheat rotation (RW) (NT-CW, CT-CW, NT-RW, CT-RW) were analyzed.  Principal component analysis of the FAME data revealed that these management systems have selected different microbial communities among the treatments studied. A total of 38 fatty acids and related compounds were identified.  More FAMEs were identified in NT treatments (between 32 and 35) when compared to CT treatments (23 to 25). Greater richness and diversity (Shannon’s diversity index) were observed in the NT treatments than in the CT treatments, which appeared to be more highly influenced by tillage treatment than cropping sequence. Richness followed the following order among treatments: NT-RW > NT-CW > CT-CW > CT-RW. Evenness was similar between treatments (0.90 - 0.92), except with the NT-RW treatment, which was lower (0.88). The ecological relevance of microbial community selection on soil C and N pools is being studied.