Reduction of ammonia emissions from dairy manure using novel urease inhibitor formulations under laboratory conditions

• Laboratory tests of urease inhibitors were performed at various temperatures.
• Decrease of reduction potential of inhibitors with increasing temperature.
• The mean reduction potential of the reference was 48%.
• The highest reduction potential showed inhibitor K with 64%.
• The mixture of different inhibitors in different ratios showed no improvement.

Ammonia emissions from livestock manure can have detrimental effects on environment, health and reduce the value of the manure as fertiliser. A promising approach for reducing ammonia emissions from dairy farming is the use of urease inhibitors. They were tested in this study under standardised conditions in a laboratory set-up. Four selected inhibitors (designated D, L, K and E) were tested in concentrations of 0.01% and 0.1% of total Kjeldahl nitrogen (TKN) and at manure temperatures of 18 °C, 20 °C and 25 °C. At 0.1% [TKN] all inhibitors showed a reduction in ammonia emissions at all temperatures settings (22 %–70 %). The reference inhibitor (D) and the modified inhibitor (L) had reduction potentials of 48% and 27%. At 20 °C inhibitor E showed no improvement in the reduction potential compared to the other inhibitors used, and was therefore not tested further. At all temperature settings, inhibitor K at concentrations of 0.1% [TKN] showed the highest reduction at 64%. Mixtures of two different inhibitors (0.1% [TKN], 20 °C) did not improve the reduction effect compared to the pure inhibitors. These ammonia reduction results showed that inhibitor K was the most promising with the potential to be used in further practical studies.