Soil microbes in organic vegetable production: Capturing the active players

The response of soil microbial communities to organic and conventional fertilization

Ceres Trust Research Grant

Authors: Lorena Gomez-Montano, Ari Jumpponen, Megan Kennelly, and Karen A. Garrett

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Soil microbial communities play fundamental roles in the productivity of agricultural systems. Organic methods may foster more diverse soil microbial communities beneficial for crop production that may reduce losses to pathogens. We evaluated active bacterial community responses, in established long-term experimental systems, to organic vs. conventional nutrient management. This graduate research project complements our main Ceres project, allowing comparisons of total resident microbial pools via sequencing the rDNA (main project for The Ceres Trust) and the active microbial pools via sequencing the RNA present in the ribosomes (this project) that are responsible for translation of the transcribed RNA into proteins. In other words, we can compare the general pool of bacteria with the bacteria that are actively metabolizing. We evaluated the microbial communities in an experiment comparing organic and conventional fertilizer systems, with low and high levels of fertility. Using one measure of diversity, Inverse Simpson’s Dominance, we found higher bacterial diversity under organic management for high fertility treatments. We recovered a number of bacterial genera that have important agroecological roles. There were more bacterial phyla that increased in frequency in DNA samples compared to RNA samples than vice versa.

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