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Title: EFFECTS OF TILLAGE SYSTEMS ON SOIL MICROBIAL COMMUNITY STRUCTURE UNDER A CONTINUOUS COTTON CROPPING SYSTEM

Author
item FENG, Y - AUBURN UNIVERSITY
item MOTTA, A - AUBURN UNIVERSITY
item BURMESTER, C - AUBURN UNIVERSITY
item Reeves, Donald
item VAN SANTEN, E - AUBURN UNIVERSITY
item OSBORNE, J - AUBURN UNIVERSITY

Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/24/2002
Publication Date: 6/24/2002
Citation: Feng, Y., Motta, A.C., Burmester, C.H., Reeves, D.W., Van Santen, E., Osborne, J.A. 2002. Effects of tillage systems on soil microbial community structure under a continuous cotton cropping system. In: Van Santen, E., editor. Proceedings of the 25th Annual Southern Conservation Tillage Conference for Sustainable Agriculture - Making Conservation tillage Conventional: Building a Future on 25 Years of Research. Special Report no. 1, Alabama Agricultural Experiment Station and Auburn University, June 24-26, Auburn, Alabama. p. 222-226.

Interpretive Summary: Soil microbes are vital to soil productivity and soil health. Soil management practices affect soil microbial communities, which can influence the soil's ability to produce crops and act as an environmental filter. We measured the effects of conventional- and no-tillage practices on soil microbial communities under long-term continuous cotton production. Soil samples were taken in winter, spring and fall at different depths. No-tillage management increased soil carbon 127% and nitrogen 70% in the soil surface, compared to conventional tillage. No-tillage also increased the quantity of soil microbes all three seasons measured. The population of different types of microbes, especially bacteria populations, shifted over time and soil depth. During the cotton growing season, changes in microbial communities were dependent on soil conditions associated with cotton plant growth and rainfall and temperature. During winter, tillage system influenced community changes more than the cotton crop. This information can be used by extension, NRCS, and private-sector consultants to promote the use of conservation tillage to improve soil quality and productivity.

Technical Abstract: Soil management practices affect soil microbial communities which, in turn, influence soil ecosystem processes. In this study, the effects of conventional and no-tillage practices on soil microbial communities were examined under continuous cotton (Gossypium hirsutum L.) systems on a Decatur silt loam soil. Soil samples were taken in February, May, and October of 2000 at depths of 0 to 3, 3 to 6, 6 to 12, and 12 to 24 cm. The no-till treatment had significantly higher soil organic carbon and microbial biomass carbon contents in the surface layer than the conventional till treatment. Microbial community structure, as indicated by phospholipid fatty acid (PLFA) profile, was analyzed using principal components analysis; analysis of variance (ANOVA) on the first two principal components (PCs) was performed to assess the effects of tillage and sampling time. PLFA profiles clearly shifted over time and along soil depths. ANOVA on PC 1 revealed that both month x depth and tillage x depth interactions were significant. The response of PC 1 was different for conventional till and no-till treatments, and for the late season and the two early season samples. The influential fatty acids to the first two PCs were 10Me16:0, i15:0, and cy19:0 which are signature bacterial PLFAs, suggesting that the observed differences may result from the shift of bacterial populations. These results indicate that microbial communities associated with conventional tillage and no-tillage continuous cotton systems were dissimilar and the tillage effect varied by soil depths and over time. The use of culture-independent methods, such as PLFA profile analysis, allows us to better characterize the changes of microbial community under different management systems and may provide insights into how conservation tillage improves soil quality and sustainability.