Ammonia sources in agriculture and their measurement

There are several reasons why the measurement of ammonia emissions is important in agriculture. The emission of ammonia from stored and land-applied manure to the atmosphere can result in a significant loss of nitrogen for crop production. It is necessary to quantify this loss to evaluate manure handling practices for maintaining the nutritive value of the manure. Minimizing the emissions of ammonia from manure also reduces agriculture's impact on the environment. A high atmospheric concentration of ammonia can result in acidification of land and water surfaces, cause plant damage and reduce plant biodiversity in natural systems. Ammonia emissions from manure coincide with odors, which are a nuisance in areas of intensive livestock operations. Reducing ammonia emissions by altering manure management will also reduce odor problems. The purpose of this paper is to review agricultural sources of ammonia and describe techniques used in determining the loss of ammonia from manure-amended soils. Micrometeorological techniques are used to estimate field scale emissions whereas, for small plots where treatment (effects) is used, chambers and mass balance techniques are more suitable methods. A simple method is described, which, when combined with a denuder sampler mounted on a wind vane, permits flexibility in experimental design and requires fewer ammonia samples than the traditional mass balance approach. A chamber method making use of diffusion samplers that can measure the ammonia concentration in the air at the soil surface is also described. Key words: Ammonia, nitrogen loss, agriculture, manure, micrometeorology, chamber