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The traditional slatted floor was compared with 2 different solid floor systems: a non-sloped (L) and a 3% one-sided sloped floor (S), combined with a highly frequent (96 times/day) or normal (12 times/day) removal of manure by a scraper. NH3 emissions were measured continuously over 2 separate 2-week periods between 14 March and 4 July 1995. Urease activity on the solid floors was measured as the accumulation of ammoniacal N in a urea solution in contact with the floor surface, expressed as g NH3/msuperscript 2 per h. NH3 emission from L12 was similar to that from the compartment with a slatted floor but S12 decreased NH3 emission by 21%. Increasing the scraping frequency from 12 to 96 times/day decreased NH3 emission (by 5 and 26% in L96 and S96, respectively). During the last testing period, just before removal of the cows, NH3 emission from the compartment with the S12 variant was 30-35 g NH3/h (10 cows). After removal of the cows this level decreased to 3-17 g NH3/h (average: 8.7 g NH3/h). Covering the openings through which the slurry collected by the scraper system was dropped in the pit, reduced emission to 4-10 g NH3/h (average: 5.5 g NH3/h). However, covering only decreased NH3 emission when the inside temperature was higher that outside. Urease activity at\less than or =\10 and approximately 20 degrees C was 0 and 0.04 g NH3/msuperscript 2 per h, respectively. Up to a urease activity of about 2 g NH3/msuperscript 2 per h, NH3 emission increased with increasing urease activity. At higher levels of urease activity the amount of urea on the floor surface or the rate of volatilization of NH3 from a urine …