| Summary: | Ammonia (NH<sub>3</sub>) concentrations in summer were continuously monitored from three typical laying hen houses of CC (conventional cage), AV (aviary), and NM (natural mating colony cage) with manure belt systems in North China Plain to quantify their emission levels, to characterize the diurnal variations, and to investigate the impact of environmental factors. Diurnal profiles were acquired by hourly measurements, and the effect of environmental factors on NH<sub>3</sub> emissions was presented by correlation analysis. The results showed that house-level NH<sub>3</sub> emissions in summer were the highest in the NM at 27.16 ± 13.12 mg/h·hen, followed by the AV at 4.08 ± 3.23 mg/h·hen and the CC at 3.43 ± 1.46 mg/h·hen within a complete manure removal cycle, which were significantly affected by manure accumulation inside the houses. After manure removal, NH<sub>3</sub> concentrations were reduced by 64.29%, 28.57%, and 35.71% in CC, AV, and NM, and consequently their emissions were lowered by 67.12%, 71.36%, and 55.69%, respectively. It was suggested that the manure should not be stored on the belt for more than 4 days in NM. A positive impact of indoor and outdoor temperature and ventilation rate on NH<sub>3</sub> emissions from AV and NM were found, while indoor and outdoor relative humidity had a negative effect. However, the above five factors did not significantly affect the emissions from CC.
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