Wednesday, August 5, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Shashi Kumar1, Rina Kumari2, Scott Dowd3, Randall M. Jeter2, Michael J. San Francisco2 and John C. Zak2, (1)Biology, Texas Tech University, Lubbock, TX, (2)Biological Sciences, Texas Tech University, Lubbock, TX, (3)Research and Testing Laboratory, Lubbock, TX
Background/Question/Methods Different crop management practices have been applied to agroecosystems in semi-arid regions to increase plant productivity and reduce inputs. Some of these management practices include reduced tillage; crop rotation, and planting winter crops. Bacterial communities are an important component of all soil systems and can influence the outcome of crop management practices. Any management practice that alters bacterial diversity and activity may significantly impact crop yield. Tillage practices, which are commonly used in farming, have an impact on the soil ecosystems. In this study we analyzed the effect of tillage practices on bacterial diversity for a peanut cropping system in semi-arid west Texas. The treatment consisted of minimal and conventional tillage nine months prior to the growing season. Plots were arranged around a center-pivot in concentric circles. The outermost circles consisted of minimal tillage followed by conventional tillage rows. Soil was collected over a five-month period (post-seedling stage, June to October) from the rhizosphere of peanut plants. DNA prepared from these samples was amplified using bacterial universal 16S-rRNA-encoding gene primers, and the products were subjected to 454 pyrosequencing. Rarefaction analysis was used to determine the influence of tillage on bacterial diversity. Bacteria were grouped at different taxonomic levels and the effects of tillage analyzed.
Results/Conclusions It was observed that in minimal tillage bacterial diversity was greater than that observed in conventional tillage treatments. Conventional tillage disrupts the soil particles, decreases the soil pore size and number leading to decreased oxygen and water to the microbes. This results in reductions in bacterial population and diversity. The most dominant bacterial group found in both treatments was Actinobacteria. Interestingly, the proportional abundance of actinobacteria was higher in the conventional tillage than in the minimal tillage treatments. The implications of these findings will be discussed.
