Impact of Tillage and Residue Management on Soil Microbial Biodiversity Under Soybean-Corn Rotation.

Soil health provides an overall picture of soil functionality that includes chemical, physical and biological features necessary for long-term, sustainable productivity.  Studies have shown that tillage has profound and complex influence on soil physical, chemical and biological properties.  A three-year study was initiated to evaluate the effects of tillage, crop rotation and residue management on soil biodiversity in a soybean production system. Soil samples were collected from ongoing field experiment that studies the effects of tillage and residue on soil quality under soybean-corn rotation scheme located at North Mississippi Research and Extension Center (non-irrigated) and Delta Research and Extension Center (irrigated) in Verona and Stoneville, Mississippi, respectively. Soil samples were collected from existing experimental plots receiving four kinds of tillage [No-till, Conservation-till (bed- roller), Conventional till (disc (2X) + Terra Till®) and Terra Till® alone] and two residue treatments [burn and no-burn (corn only)] in a corn-soybean rotation system. The bacterial community change at the No-Till (NT) plots was significantly different from the other sites as explained by the axis of maximum variability from Bray-Curtis ordination (Axis 1= 76 %). There was no significant difference in the pattern of bacterial OTU distribution between other tillage management patters. However, there was a moderate location effect along the minor axis of variation (Axis 2= 4 %) and bacterial community composition at Verona was significantly different from Stoneville plots. The year 1 (2013) results suggest that tillage had a profound effect on biomass and composition of soil microbial communities. Initial results showed that the tillage effect on composition of soil microbial communities was very pronounced in the short term, but the effect of crop rotation was probably built in the long term. Results from subsequent years would help to analyze the impact of crop rotation on soil health attributes under corn-soybean production systems.