Cold season ammonia emissions from land spreading with anaerobic digestates from biogas production

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.