Effect of nutrition and management factors on ammonia emission from dairy cow herds: models and field observations

In the Netherlands and other regions with a high density of farm animals, it is important to reduce ammonia emission, which causes undesirable deposition of nitrogen in ecosystems with a low nitrogen demand and is also involved in environmental acidification. On a dairy farm, the main sources of ammonia emission are the cow house, the grazed pasture and manure application in the field. In this paper, we present a model approach for each of these sources. On the basis of data collected from commercial herds, we also discuss some effects of management on ammonia emission. To validate the cow-house model, we used data from an experiment with several diets that influenced ammonia emission from a cow house. When used under experimental farm conditions for a wide range of diets and indoor climate conditions, this model accurately predicted NH3 emissions from a dairy cow house. Important roles in the options for reducing ammonia emission (whether per cow, per hectare, or per herd) are played by the intensity of farming (i.e. cows per hectare), manure application technique, fertiliser rate, feeding management and grazing management. We will continue to validate the model results by measuring the emissions from the different sources at several commercial farms. (C) 2003 Elsevier B.V. All rights reserved.