Does Long Term No-Tillage Change the Distribution and Abundance of Bacteria, Archaea and Nitrifier Communities in a Drip Irrigated Agriculture System?.

The abundance and distribution of microbial communities was evaluated at five time points over a growing season to look at the impacts of tillage on soil microbial communities.    A long term no-tillage experiment in the San Joaquin Valley, California provides a unique opportunity to look at microbial community shifts after 15 years on no-till drip-irrigated agricultural system.   Reduced soil disturbance by no-till management, has been shown to change the physical and chemical properties of soil in many regions.  In this soil total soil carbon and nitrogen has increased in the surface soils of cover cropped and no-till treatments. We addressed potential shifts in community abundance and distribution through quantitative PCR to measure abundance of bacteria, archaea and fungi, as well as genes that code for ammonium oxidation in bacteria and archaea (amoA).  This experiment evaluated how long-term disturbance and differences in soil properties such as aggregate stability, total C and total N, lead to different microbial community composition and distribution.