Increasing temperature is known to increase diffusion when all other factors are held constant. However, freezing/thawing sequences, snow cover, and soil and air temperature variations alter many other factors, as well, which also impact diffusion. Diffusion theory will be reviewed with a focus on ammonia, methane, nitrous oxide, and carbon dioxide diffusion within soil and from soil to the atmosphere. Soil temperature can alter the production of these gases by influencing the microbial environment. Freezing and thawing cycles can alter soil structure and, thereby, reduce tortuosity and allow for more rapid gaseous diffusion. Properties of snow cover such as depth and density also alter the movement of gases through the snow barrier. Temperature may also affect soil adsorption of ammonium and hence influence release of ammonia to the atmosphere. Air temperature impacts the vapor pressure of the air, and hence can alter the concentration gradient which drives diffusion. All of these processes have great significance in terms of global warming, but they also have practical significance in the areas of optimizing efficiency of N use from fertilizer and organic N sources, shifting N losses from nitrate losses to groundwater towards gaseous losses to volatilization and denitrification, odor control (ammonia and methane) from livestock production units and manure storage facilities, and methane losses from landfills. Research needs will be identified. Implications for management of N and C cycles in livestock and crop production and rural and urban waste management will be discussed.

Jessica G. Davis
Department of Soil and Crop Sciences
Colorado State University
Fort Collins, CO 80523-1170   U.S.A.
Phone (970)491-1913
FAX (970)491-0564
Email: jgdavis@lamar.colostate.edu