Spatial Analysis of the Nitrogen Cycling Microbial Communities in Agricultural Soils.

The process of nitrogen cycling is of paramount importance in agricultural soils, as nitrogen is often a limiting nutrient for plant growth. In addition, the loss of nitrogen as nitrate or nitrous oxide (N₂O), a potent greenhouse gas, can lead to a number of serious environmental issues. The main objective of this study is to determine if different agricultural management practices affect the nitrogen cycling microbial community, as well as, nitrogen use efficiency in these systems.  The different management practices being compared are a new fertilizer application mechanism, sub-surface banding of poultry litter, and a traditional broadcasting approach, as well as, two cover cropping systems, hairy vetch (Vicia villosa), and cereal rye (Secale cereal).  This study is unique in that it relates these management practices to the microbial communities and nitrogen cycling functional guilds which control the nitrogen transformations in the soil. In order to investigate these processes, a spatial sampling grid was set up horizontally across the intterow and vertically from the top of the soil surface down to 30 cm. For this study ammonia and nitrate are analyzed for each sample as well as a suite of nitrogen cycling functional genes ureC, amoA, nirK, nirS, nosZ2, and 16S. We hope to give insight into the environmental controls on the nitrogen cycling microbial community, the nitrogen transformations occurring in the soil, and relate this information to larger scale processes such as nitrogen efficiency of different fertilizer management techniques and N₂O emissions from agricultural soil.