Monday, 7 November 2005
7

Occasional Tillage of No-Till Systems: Short-Term Effects and Recovery Dynamics of Soil Microbial Communities.

Juan A. Quincke, Martha Mamo, Charles S. Wortmann, and Rhae Drijber. Univ. of Nebraska, Dept. of Agronomy and Horticulture, 279 Plant Sciences, Lincoln, NE 68583-0915

The typically high stratification of soil properties in long-term no-till systems comprehends chemical, physical and microbial attributes, and has resulted in soil quality improvements occurring mostly in the top 5 cm of the profile. Occasional tillage for no-till systems is proposed as a single, one-time tillage, conducted once in 12 or more years, to invert the highly improved surface layer with less improved deeper soil. This presents an opportunity to further improve agronomic and environmental performance of no-till systems. We hypothesize that occasional tillage will result in an overall enrichment with fungi and rhizospheric microbes of the soil profile, even though significant short-term losses of these microbes may occur in the surface 5 cm following tillage. Objectives were (1) to determine the change in the soil microbial community after a one-time tillage of a long-term no-till system, and (2) to establish the recovery dynamics of the soil microbial communities over one or two cropping seasons following tillage. Two experiments in long-term NT fields were installed under rainfed corn or sorghum rotated with soybeans in Eastern Nebraska. Fatty acid methyl ester (FAME) profiles were used to ‘fingerprint' soil microbial communities in response to following tillage treatments: continuous no-till, moldboard plow and mini-moldboard plow. Soil samples were taken at planting or shortly after at the following depths: 0–5, 5-20, and 20-30 cm. Results will be relevant for discussing the feasibility of occasional tillage in no-till systems and the potential for improving soil microbial quality.

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