Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2010
Publication Date: 1/11/2011
Citation: Rice, W.C., Gowda, P. 2011. Influence of geographical location, crop type, and crop residue cover on bacterial and fungal community structures. Geoderma. 160:271-280.
Interpretive Summary: The interaction of geographical distance, non-biological and biological factors, and agricultural management practices was evaluated (using DNA markers) for their ability to influence microbial community structure. This study was conducted in the Texas High Plains region. All of these factors when considered either singly (geographical distance, crop type, and residue coverage) or in combination (distance-crop type, distance-residue coverage, and crop type-residue coverage) were shown to influence overall bacterial and fungal community composition. Distinctive influences of location i.e. Moore vs. Ochiltree were evident in the shift in community structure for both bacterial and fungal communities. Thus climatic and geographical features were shown to influence community microbial composition. Crop type appeared to be a stronger influence of bacterial and fungal community composition than did residue coverage. For sorghum and wheat grown in Moore and Ochiltree Counties, we have defined a two province state comprised of four habitats i.e. sorghum and wheat assemblages influence by residue state.
Technical Abstract: The objective of this study was to evaluate the effects of geographical location, crop type and residue coverage on soil microbial assemblages in Sherm soil from 30 geographically separate commercial fields in Ochiltree and Moore Counties of Texas. Crop residue coverage was derived from spectral data and used to classify sorghum and wheat fields into high and low crop residue categories. Denaturing gradient gel electrophoresis-polymerase chain reaction (DGGE-PCR) assays employing universal PCR primers that target prokaryotic and eukaryotic ribosomal genes were used to evaluate microbial community structure. An interaction between geographical location, crop type, and crop residue coverage was observed. A 50% similarity level was observed for overall bacterial community structure as determined using 16S data while a 59% similarity was observed for overall fungal community structure using 18S data. For the 16S composite dataset, high overall rate of correct classification (ORCC) were observed based on the user-defined groups of county by crop by residue coverage. A similar result was observed for fungal community structure using primer set FR1GC-FF390. Our data support the hypothesis that there are multiple provinces and multiple habitats that govern the assemblage of free-living taxa within the Moore-Ochiltree County agroecosystem. An ancient microbial assemblage based on historical features was identified and is still visible despite the presence of different crop types and cropping systems (Conventional vs. Conservation). For sorghum and wheat grown in Moore and Ochiltree Counties, a two-province state (Moore and Ochiltree Counties) was defined comprised of four habitats i.e. sorghum and wheat habitats influence by residue state. Crop type and residue coverage can affect microbial assemblages within a geographical context.