Estimating ammonia emitted from manure during storage on a dairy farm

Abstract

<b><sc>Abstract.</sc></b> Manure storage is an essential aspect of nutrient management on dairy farms. A substantial amount of nitrogen is lost as ammonia (NH₃) from manure during storage. The NH₃ emissions can adversely impact the local environment and one of the primary sources of nitrogen pollution. This study quantified the NH₃emissions from a clay-lined manure storage structure on a dairy farm. The NH₃concentrations were measured using Ogawa passive samplers over 10 months, and the NH₃ flux was calculated using WindTrax dispersion model. The NH₃flux varied between 3.02±0.12 µg/m²/s and 15.3±0.57 µg/m²/s, averaging 6.19±0.24 µg/m²/s. About 25% of the emissions occurred during and right after the manure removal events when there was weak or no crusting on the manure surface. Crust removal caused the highest increase in NH₃emissions. The manure temperature, manure depth, and the prevailing meteorological conditions (e.g., ambient air temperature, wind speed, and wind direction) were concurrently measured on the farm. The NH₃emissions were significantly correlated with the manure temperature, ambient air temperature, and wind speed (P < 0.05). The wind speed was the most substantial meteorological influence; higher wind speeds considerably increased the emissions. Finally, the NH₃ flux followed the manure temperature trend more closely than the ambient air temperature.