It's an impact that caught most people by surprise. Similar questions could crop up in the Bay watershed. Some people, for example, are concerned that certain recommendations for dealing with animal manure stemming from last year's pfiesteria outbreak have the potential to increase ammonia volatilization. The amount of ammonia lost through various agricultural practices has been examined for years, though not from a water quality standpoint. As a rule of thumb, said Jack Meisinger, of the U.S. Department of Agriculture's Agricultural Research Service, about 30 percent to 50 percent of the nitrogen in animal wastes volatilizes into the air as ammonia from the time it is excreted until it is placed into storage.
More ammonia is lost into the air when the manure is spread onto fields.
Exactly how much is lost depends on a variety of factors. Warm, windy or low humidity weather can increase volatilization. Under such conditions, a third to half of the remaining nitrogen could vanish from the manure. But if the farmer plows the manure into the soil, the loss during application can be reduced to almost zero. Urea-based fertilizers, the most common in the watershed, can also lose a large portion of their nitrogen to ammonia volatilization, depending on their method of application.