Influence of geographical location, crop type and crop residue cover on bacterial and fungal community structures

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 rates 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 degree of residue coverage. Crop type and residue coverage can affect microbial assemblages within a geographical context. Published by Elsevier B.V.