To effectively make use of manure N analyses in conservation planning, a two pool model with estimates of ammonia N loss and organic N mineralized is needed to estimate plant-available N provided by manure.  Two-pool models have been used for 20+ years in other parts of the U.S., but this approach has not been widely adopted in the West.  This presentation reviews ammonia loss at the field scale, emphasizing management effects on ammonia loss.  The goal is to describe the probability of ammonia loss for particular soil, climate, and manure characteristics in a way that will be useful to conservation planners.  The most robust and simple ammonia loss model identified by this literature review is ALFAM (Ammonia Loss from Animal Manures, www.alfam.dk).  This model predicts ammonia loss following application using the following manure and environment inputs: soil moisture, air temperature, wind speed, slurry type, slurry dry matter %, total ammoniacal N, application technique, application rate, slurry incorporation method.   ALFAM uses these soil and environmental factors to modify a Michaelis-Menten function describing ammonia loss over time.   A model like ALFAM can be linked to real time or historical weather data for a site or region to give approximations of ammonia loss in response to management  and site variables.  This review will also address other topics somewhat unique to the arid and semi-arid west such as ammonia loss associated with irrigation and with calcareous soils.