CONCEPTUAL MECHANISTIC MODEL FOR THE AMMONIA EMISSIONS FROM FREE STALL CUBICLE DAIRY-COW HOUSES

A conceptual model, consisting of floor and slurry pit modules, for es timating ammonia emission from cubicle (free stall) dairy cow houses w as developed. Components in the floor module described urine depositio n, 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 with mea surements of ammonia emissions from January to June for a commercially operated, mechanically ventilated research cow house. Maximal underes timation was 6% and maximal overestimation was 7%. A sensitivity analy sis on the input parameters for which measured data were unavailable s howed that urease activity had little effect on the simulated emission and that the largest effect was due to pH. The reliability of the mod el for predicting ammonia emission for practical conditions will mainl y depend on the validity of assumptions concerning the time independen t character of most of the parameters and on the accuracy with which p arameters can be determined.