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Title: SOIL MICROBIAL COMMUNITIES UNDER CONVENTIONAL-TILL AND NO-TILL CONTINUOUS COTTON SYSTEMS

Author
item FENG, Y - AUBURN UNIVERSITY
item MOTTA, A - AUBURN UNIV.STUDENT
item Reeves, Donald
item BURMESTER, C - AUBURN UNIVERSITY
item VAN SANTEN, E - AUBURN UNIVERSITY
item OSBORNE, J - N.C. STATE UNIV.

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2003
Publication Date: 9/2/2003
Citation: Feng, Y., Motta, A.C., Reeves, D.W., Burmester, C.H., Van Santen, E., Osborne, J.A. 2003. Soil microbial communities under conventional-till and no-till continuous cotton systems. Journal of Soil Biology and Biochemistry. 35(12):1693-1703.

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 long-term 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. Compared to the conventional-till treatment, the no-till treatment increased soil organic carbon (SOC) and total nitrogen contents in the surface layer by 127 and 70%, respectively. Microbial biomass C content under no-tillage was 61, 138, and 75% greater than with conventional-tillage in February, May, and October, respectively. Principal components analysis of phospholipid ester-linked fatty acid (PLFA) profile indicated soil microbial communities shifted over time and soil depth. This change appeared to be driven primarily by soil bacterial populations. Tillage treatment differences were revealed by analysis of variance on the first principal components (PC 1), which accounted for 62% of the total sample variance, and by the relative abundance of selected PLFAs and PLFA ratios. The impact of tillage practices was significant in February and May, but not in October. During the growing season, changes in the microbial community may be primarily determined by soil conditions responding to cotton growth and environmental variables such as moisture and temperature; during fallow or prior to cotton establishment, community changes associated with tillage practices become more pronounced. These findings have implications for understanding how conservation tillage practices improve soil quality and sustainability in a cotton cropping system.