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Ammonia emissions damage the environment and have negative consequences for human and animal health. In the German livestock sector, most ammonia emissions come from naturally ventilated dairy barns. To reduce emissions, Germany has signed the EU Directive 2016/2284 to achieve a stepwise decrease in the ammonia emissions ceiling. The aim of this study was to investigate the seasonal mitigation effect of a urease inhibitor under practical conditions and provide information relating to two theoretical application scenarios in order to estimate an annual application scenario. The experimental design was conducted according to the requirements of the Verification of Environmental Technologies for Agricultural Production test protocol using the CO2 balance method to obtain the emissions. In a manual process, the inhibitor was applied to the floor surfaces of two dairy farms. The application took place once a day over three days during summer, winter and the transition period (spring/autumn). The ready-to-use liquid formulation of 1% inhibitor K dissolved in pyrrolidone was mixed with water resulting in 2.5 mg m−2 application rate of inhibitor and 50 ml m−2 water. The ammonia emissions on Farm A and Farm B were reduced by 40% and 53% in summer, 65% and 68% in winter and 64% and 54% in transition period, respectively. Thus, an annual reduction of 58% on Farm A and 57% on Farm B was observed. In a theoretical scenario where no inhibitor was applied during winter, up to 41% of the annual reduction was observed.

Ammonia emissions have wide-ranging negative consequences for human, animal and environmental health. Regulations including EU Directive 2016/2284 require European Union member states to reduce emissions. Dairy farming has one of the highest levels of ammonia emissions. Most dairy barns in Germany are naturally ventilated to meet higher animal welfare standards. However, these housing systems allow an uncontrolled direct release of emissions into the atmosphere. A novel mitigation method could be the use of a urease inhibitor. Although previous studies have noted the reduction potential of the inhibitor type K, the chronological course of the reduction is still unknown. This study investigates the inhibitory reaction by dividing the experiment into time slots to examine the chronological reduction in emissions. The inhibitor was found to reduce ammonia emissions by up to 37% at the 12-h time slot. This supports the assumption that the reduction potential of the inhibitor evolves over time.

The reduction of ammonia emission from animal husbandry is required due to detrimental and harmful effects on environment, health and fertilizer value. Nevertheless, practicable measures with a high ammonia mitigation potential, which can be implemented in existing dairy housing systems without significant constructional changes, are still rare. A possible reduction option, not previously used in practice, is the application of urease inhibitors on floor surfaces in dairy houses. Urease inhibitors inhibit the enzyme urease, which is responsible for the release of ammonia. It can, therefore, be assumed that a reduction of the urease activity always results in ammonia mitigation. Cubicle housing systems for dairy cattle differ in technical, climatic and organizational conditions. Consequently, tests on three different housings in three seasons have been carried out in the current study to evaluate the use of urease inhibitor in practice. The effect of the urease inhibitor was investigated based on detection of urease activity. A significant correlation of floor surface temperature and level of urease activity was observed. The current study shows that the application of a novel urease inhibitor resulted in overall average reduction of urease activity of 80% at dairy housing systems and at different seasons.

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.