Effects of floor design and floor cleaning on ammonia emission from cubicle houses for dairy cows

Abstract

To obtain more detailed knowledge of low-emission floor systems for dairy cow houses an experiment was set up in which the traditional slatted floor and two different solid floor systems were compared: a non-sloped (L) and a 3% one-sided sloped floor (S), both systems combined with a highly frequent (96 times per day) or normal (12 times per day) removal of manure by a scraper. For both the slatted and solid floor systems ammonia emissions were measured continuously over two separate two-week periods. On the solid floors also the development of urease activity was recorded. Urease activity was measured as the accumulation of ammoniacal nitrogen in a urea solution (10 g urea-N 1-1) in contact with the floor surface. Activity has been expressed as g NH3 m-2 h-1. The ammonia emission from the compartment with the L12 variant was almost equal to the emission from the compartment with a slatted floor. The S12 variant reduced ammonia emission by 21% compared to the slatted floor. Raising the scraping frequency from 12 to 96 times per day led to a 5 percentage point increase in ammonia emission reduction (L96: 5%; S96: 26%). During the last testing period, just before removal of the cows, ammonia emission from the compartment with the S12 variant was 30-35 g NH3 h-1 (10 cows). After removal of the cows this level decreased to 3-17 g NH3 h-1 (average: 8.7 g NH3 h-1). This suggested incomplete suppression of ammonia emission from the slurry pit by the solid floor system. 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-1 (average: 5.5 g NH3 h-1). However, covering only decreased ammonia emission when the inside temperature was higher than the outside temperature. The rate of formation of urease activity differed considerably between the two-week periods, partly due to differences in temperature regime. At and below 10°C average daily temperature almost no formation of urease activity was observed, whereas at about 20°C the formation rate reached values up to about 0.04 g NH3 m-2h-2. Up to an urease activity of about 2 g NH3 m-2h-1, ammonia emission increased with increasing urease activity. At higher levels of urease activity either the amount of urea on the floor surface or the rate of volatilization of ammonia from a urine puddle or from the slurry pit to the inside air limited the ammonia emission.