Effects of zonal tillage on the spatial variability of soil microbial communities

Background/Question/Methods

Microbial-mediated soil processes control many ecological services in natural and human-managed systems. Spatially explicit management strategies focused on microbial ecosystem services at sub-meter scales may help us create systems where seemingly incompatible processes can exist side-by-side. In agriculture, idge-tillage (RT) is a type of zonal management system that creates spatial heterogeneous soil environments in two zones: ridge (crop row) and furrow (interrow) areas. Unique biological, chemical and physical characteristics are developed in ridge and furrow, respectively, attempting to manage for microbial communities that support soil building and crop extraction of soil resources. Thus, it is important to understand the differentiation of microbial communities and functional groups in these two distinct zones. A multi-state study of soil bacterial and fungal communities was conducted on four agricultural fields with RT and non-zonal conventional tillage. Microbial communities were assessed by automated ribosomal intergenic spacer analysis (ARISA), and the population size of nitrifying microorganisms was determined by real time quantitive PCR. Differentiation of communities across the row and interrow was calculated by Bray-Curtis dissimilarity, and classification and regression trees (CART) were used to model associations between zonal microbial differentiation and state, tillage system, cover crop, soil depth and residues decomposition.

Results/Conclusions

Soil depth and residue decomposition had significant impacts on bacterial and fungal communities cross all four states (P<0.05). In most of states, cover crop also had significantly impacts on bacterial and fungal communities (P<0.05), except in Michigan and fungal community in Pennsylvania. Regression tree show that zonal systems generates more spatially heterogeneous microbial communities than non-zonal systems. In general, residue decomposition under RT increased the abundance of ammonia-oxidizing archaea (P<0.05), but not ammonia-oxidizing bacteria. Agricultural soils can be managed for distinct, sub 5cm soil zones that differ in microbial community composition. Crop residues decomposed in zonal system enhanced soil potential of archaea ammonia oxidization.