Conservaton Tillage Impacts Soil Microbial Community Structure and Function in a Long-Term Maize-Soybean Cropping System.

To be entered.

Conservation Tillage Impacts Soil Microbial Community Structure and Function in a Long-Term Maize-Soybean Cropping System

Hussein Alserae¹, Virginia L. Jin², Humberto Blanco-Canqui¹, Marty R. Schmer², Rhae A. Drijber¹,

¹Dept of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE.

²UNL- East Campus, USDA-ARS, Lincoln, NE.

Conservation tillage and crop rotation are two management variables known to have beneficial effects on soil microbial community structure and function largely through impacts on soil properties. The long-term relevance of this to microbial communities and extracellular enzyme activities (EEA) within corn-soybean systems dominant in the central Great Plains was evaluated within the top 30 cm of soil after 29 years of tillage practices varying in intensity from no-till (NT) to chisel plow (CP) to disk (DT) to moldboard plow (MP) under continuous corn (CC), continuous soybean (SS) and corn-soybean rotation (CS). Soil microbial biomass (SMB) and community structure was assessed using fatty acid methyl ester (FAME) analysis. The extracellular enzymes included nine enzymes important to C, N, P and S cycling. Regardless of the method of tillage or crop rotation, SMB and EEA was significantly higher in the first 0-15 cm depth than the second depth 15-30 cm (p<0.05). Total SMB, bacteria, actinomycetes, and arbuscular mycorrhizal fungi (AMF) were higher under NT compared to the remaining tillage systems (p<0.05). In contrast, saprophytic fungal biomass was greater under MP. Canonical discrimination analyses of FAME and EEA data demonstrated distinct differences in soil microbial communities (FAME) and their potential activities (EEA) among tillage practices and cropping systems. Separation of tillage practices based on FAME profiles was strongest in the 0-15 cm depth, while EEA separated tillage more strongly in the second depth. Monocultures were clearly separated from corn-soybean in rotation, occupying the extremes on the first canonical axis for both FAMEs and EEA. The highest EEA were generally found under NT, while SS had the least EAA. Implications of soil and crop management on soil microbial community structure and function will be discussed in the context of long-term corn-soybean cropping systems.