VATIS UPDATE Article

Researchers from the University of Eastern Finland, the University of Helsinki, Finland and the Natural Resources Institute, Finland, have applied the eddy covariance technique combined with the most-modern laser technology in the market to measure nitrous oxide emissions from a field where a bioenergy crop was cultivated (Maaninka, Eastern Finland). In the early summer, the nitrogen availability in the soil was high after the nitrogen fertilization. Nitrous oxide emissions were high during this time. The emissions, however, had significant diurnal variation. The emissions were higher during daytime than during night time.

The researchers explained these results by the variation in soil temperature and moisture. Later in the growing season when the effect of nitrogen fertilization diminished, the diurnal variation in the emissions changed surprisingly. Then the emissions were higher during night time. Excluding the diurnal variation in nitrous oxide emissions causes inaccuracies in the annual emission estimates. The results support the development of reliable measuring methods for nitrous oxide emissions and improve our understanding of the nitrous oxide emission mechanisms and their controlling factors.

Competition for soil nitrogen between plants and microbes has a crucial role for the nitrous production in the soil. When soil nitrogen availability is low, nitrous oxide emissions are higher during night-time than during daytime because plants do not consume soil nitrogen at night and more nitrogen is available for microbes and their nitrous oxide production. Stable isotope experiments with labelled nitrogen fertilizer additions confirmed the higher night time emissions observed by the eddy covariance technique. The results have been published in the scientific journal Scientific Reports.