Irrigated crops in the Columbia Basin of Washington State occupy an area of approximately 0.5 million hectares. These crops, particularly potatoes and corn, are intensively managed, commonly receiving nitrogen inputs greater than 300 kg ha-1. In this region, unaccounted mass in nitrogen budgets are usually assumed to be lost as NO3- in the drainage or runoff water, although a significant portion could be lost in gaseous form. Information on the timing and quantity of these gaseous losses is lacking.

Our overall goal is to improve our understanding of the loss of gaseous nitrogen species from irrigated croplands to provide a better basis to account for the impact of these emissions upon regional air quality and global climate change. The first step to achieving this goal is measuring NH3 and N2O fluxes from intensively managed agricultural systems.

NH3 was measured using a short-path differential optical absorption spectroscopy (DOAS) instrument. The amount of light absorbed is relative to the number of gas molecules in the measurement path length. A tracer release technique and inverse emissions modeling were used to estimate emission fluxes from the field using the measured NH3 mixing ratios. N2O was measured using chamber flux methods and gas chromatograph analysis. Results from measurements conducted in 2007 and 2008 will be presented.