[Effects of long-term tillage measurements on soil aggregate characteristic and microbial diversity]

Soil aggregate stability and microbial diversity play important roles in nutrient recycling in soil-crop systems. This study investigated the impacts of different soil tillage systems on soil aggregation and soil microbial diversity based on a 15-year long-term experiment on loess soil in Henan Province of China. Treatments included reduced tillage (RT), no-tillage (NT), sub-soiling with mulch (SM), wheat-peanut two crops (TC), and conventional tillage (CT). Soil aggregates were separated by wet sieving method, and soil microbial (bacterial, archaeal and fungal) diversity was examined by using the techniques of denaturing gradient gel electrophoresis (PCR-DGGE) analysis. The results showed that water-stable macroaggregates concent (R0.25) and the mean mass diameter (MWD) in the surface soil significantly increased under NT, SM and TC, R0.25 increased by 21.5%, 29.5% and 69.2%, and MWD increased by 18.0%, 12.2% and 50.4%, respectively, as compared with CT. Tillage practices caused changes in bacterial, archaeal and fungal community compositions. With NT, SM and TC, the bacterial, archaeal and fungal Shannon indices increased by 0.3%, 0.3%, and 0.6%, and 20.2%, 40.5%, and 49.1%, and 23.7%, 19.5%, and 25.8%, respectively, as compared with CT. Both bacterial and archaeal Shannon indices were significantly correlated with the indices of R0.25 and MWD, while the fungal Shannon index was not significantly correlated with these two indices. In conclusion, conservation tillage, including NT and SM, and crop rotation, including TC, improved soil aggregation and soil microbial diversity.