Anaerobic digestates (AD) from biogas production are applied to agricultural land as organic fertilizers, but pose an ammonia (NH ₃) emission source. However, data about NH ₃ emissions of cold season AD land spreading is still lacking. Therefore, in the present study NH ₃ emissions of AD application under winter conditions were determined. AD was applied via trail hoses to a field plot of 27ha in Northern Germany during the winter with temperatures around the freezing point and partly frozen soil. NH ₄ ⁺ N application rate was, including a preceding urea application, 123kg NH ₄ ⁺ and urea N ha ^-1. The NH ₃ volatilization was monitored using Open Path Fourier Transform Infrared spectroscopy in combination with a micrometeorological transport model. Cumulative NH ₃ volatilization during the six day measurements was 17.5kgNH ₃ Nha ^-1 which corresponds to 33.1% of the NH ₄ ⁺ N in applied AD. This NH ₃ loss is relatively high for low temperature conditions and was most likely caused by the frozen soil restricting AD infiltration.