Volatilization of Ammonia from Dairy Housing Floors with Different Surface Characteristics

The relation between surface characteristics and urease activity was studied for samples (300×300 mm) from 50 different specimens representative of concrete floors in dairy cow houses, since volatilization of NH₃from urine pools on floors is reduced when urease activity on the floor surface is reduced, provided that urease activity is below a certain level. Variations within the factors “concrete strength”, “treatment of the fresh concrete surface”, “curing time” and “treatment of the hardened concrete surface” were applied. The specimens were split into two groups, namely non-coated and coated specimens.Floor surface roughness was measured for samples from all specimens, and also water penetration depth was measured for samples of the non-coated specimens. Samples from all 50 specimens were fouled with cow faeces and urine for 15 days and urease activity was measured.By relating urease activity of the samples from the non-coated specimens to the roughness of the floor surface and the water penetration depth, 67% of the variance was explained. This was 25% for the coated specimens, using a relation between surface roughness and urease activity. By expressing urease activity on the non-coated specimens as a function of the factors “concrete strength”, “treatment of the fresh concrete” and “curing time” and the factor levels within, 87% of total variance was accounted for.Although the experimental fouling period was relatively short compared with the length of the animal housing period, urease activity on most of the non-coated samples, on average, reached values out the range in which a reduction of volatilization of ammonia from a urine pool is found when urease activity is reduced. Coated specimens in general and, in particular, non-coated specimens of which the mould side was tested, demonstrated urease activities within that range.The durationof the fouling period during housing of the cows and the basics of the formation of urease activity on floor surfaces both support the idea that build up of urease activity proceeds after 15 days of fouling. The urease-active top layer on the floor surface is expected to cause gradual diminishing of the influence of floor surface characteristics on emission of ammonia from urine pools deposited on the floor. High levels of urease activity were expected to develop on all types of floors, either coated or non-coated. Impregnating and coating of floors in dairy cow houses were therefore not expected to result in a reduction of emission of ammonia. Only floor cleaning strategies removing or inactivating the urease on the floor were expected to result in such a reduction.