Tracing Nitrogen in the Pedosphere and Hydrosphere of Agricultural Plots near Lethbridge, Alberta using Isotopic Techniques
Lam, C.. 2013. University of Calgary ™M.Sc.
Abstract
The source(s) and fate of nitrogen in soils and in shallow groundwater beneath agricultural plots with different fertilizer amendments were determined using isotopic techniques for an experimental field located near Lethbridge, Alberta. Isotopic compositions of nitrogen and of oxygen were determined for soil total nitrogen, soil nitrate, and groundwater nitrate. Treatment differences and temporal trends in groundwater nitrate concentrations indicated that synthetic fertilizer and fixed nitrogen had an impact on groundwater nitrate. Isotopic analyses identified mineralization of soil organic matter as the main source of soil and groundwater nitrogen, whereas fertilizer, fixed nitrogen, and manure did not appear to have had a large direct contribution. This may have been due to alteration of the original isotopic source signals of fertilizer, fixed nitrogen, and manure by nitrogen transformation processes (nitrification and denitrification) during nitrogen cycling in the soil and groundwater. Denitrification occurred in the groundwater within the three-year study period.
