Submitted to: European Journal of Soil Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2009
Publication Date: 1/1/2010
Citation: Caesar, T., Lenssen, A.W., Caesar, A.J., Sainju, U.M., Gaskin, J.F. 2010. Effects of tillage on microbial populations associated to soil aggregates under dryland spring wheat system. European Journal of Soil Biology. 46:119-127.
Interpretive Summary: The purpose of this study was to determine whether or not tillage spring wheat in dryland has an influence on the proportion of microorganisms that are associated to soil aggregation. In the upper surface (0-5 cm soil depth), no till increased the proportion of the predominant soil aggregating bacteria and basidiomycete fungi in soil microaggregates compared to conventional tillage probably by increasing organic matter content that are the source of energy and nutrients for microorganisms. In addition, the techniques to isolate the predominant bacteria in soil microaggregates and to determine their potential function as soil aggregators might provide a useful and rapid assessment of the effects of external disturbances, such as tillage on soil functioning.
Technical Abstract: Tillage may influence the proportions of microorganisms involved in soil aggregation. We evaluated the effects of no till (NT) and conventional tillage (CT, tillage depth about 7 cm) continuous spring wheat system on bacterial communities predominant in microaggregates (0.25-0.05 mm) and on saprophytic basidiomycete fungi in aggregate-size classes (4.75-2.00, 2.00-0.25, and 0.25-0.05 mm) at 0-20 cm depth of a Williams loam (fine-loamy, mixed, Typic Argiborolls) in semiarid eastern Montana, USA. Enzyme-linked immunosorbent assay used to quantify basidiomycete fungi, was higher in NT than in CT in 4.75-2.00 mm size class in 2007 and higher in all size classes and years at 0-5 cm depth, but was not different between tillage, years, and aggregate-size classes at 5-20 cm. The predominant bacteria from microaggregates were subjected to a soil sedimentation assay to determine their soil binding capability. The proportion of isolates which can function as soil aggregators was higher in NT than in CT at 0-5 cm but was not different at 5-20 cm. Our results provide a first insight into the beneficial effects of dryland NT compared to CT in probably reducing soil disturbance and residue incorporation and enriching the proportion of microorganisms responsible for aggregation, especially at the surface soil.