Investigating the Effect of Management on Agricultural Organic Nitrogen Cycling and Alternative Nitrification Pathways

Abstract

This project studied the influence of agricultural management strategies (such as tillage and fertilizer choice) on nitrogen (N) cycling pathways. Soil samples and leachate samples from a series of experimental plots at the Wye Research and Education Center were analyzed using a combination of traditional chemical N measures (DON, PMN, NOx, NH3, TN, and microbial biomass C & N) and novel mass spectrometry techniques (FT-ICR-MS) to characterize shifts in organic matter composition and quantity over time and under three different cover cropping regimes. Analysis of these samples indicate that the DOM (dissolved organic matter) composition of leachate changed significantly with increasing sampling depth. However further research is needed to fully investigate the potential impacts of cover cropping and time on soil and leached DOM and DON. Soil samples were also collected at the Farming Systems Project in Beltsville, MD and at several of the University of Minnesota’s Outreach farms. These samples were analyzed for their abundance of 16S, nirK, nirS, nxrA, and amoA AOB to characterize the nitrifying and denitrifying microbial communities under a combination of management strategies. While the findings were not significant, they indicate that fertilization and tillage may have an impact on the nitrification and denitrification communities.