A conceptual model, consisting of floor and slurry pit modules, for estimating ammonia emission from cubicle (free stall) dairy cow houses was developed. Components in the floor module described urine deposition, enzymatic conversion of urea,dissociation of ammonia, and ammonia volatilization. Slurry pit module components described urine and feces production, and ammonia dissociation, and volatilization. Validity of the model was tested by comparing results on a monthly basis withmeasurements of ammonia emissions from January to June for a commercially operated, mechanically ventilated research cow house. Maximal underestimation was 6 and maximal overestimation was 7. A sensitivity analysis on the input parameters for whichmeasured data were unavailable showed that urease activity had little effect on the simulated emission and that the largest effect was due to pH. The reliability of the model for predicting ammonia emission for practical conditions will mainly depend onthe validity of assumptions concerning the time independent character of most of the parameters and on the accuracy with which parameters can be determined.
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