Whole-year-round observation of N₂O profiles in soil: A lysimeter study

Despite many studies of the N₂O emission, there is a lack of knowledge on the role of subsoil for N₂O emission, particularly in sandy soils. To obtain insight into the entrapment, diffusion, convection and ebullition of N₂O in the soil, the N₂O concentration in the soil atmosphere was measured over a period of 1 year in 4 lysimeters (agricultural soil monoliths of 1 m2 × 2 m) at 30, 50, 80, 155, and 190 cm depth with altogether 86 gas probes. Additionally the N₂O emission into the atmosphere was measured in 20 closed chambers at the soil surface. Concurrently the soil temperature and soil water content were recorded in order to quantify their effects on the fate of N₂O in the soil. Results of the continuous measurements between January and December 2006 were: N ₂O concentrations were highest in the deeper soil; maximum concentration was found at a depth of 80 cm, where the water content was high and the gas transport reduced. The highest N₂O concentration was recorded after 'special events' like snowmelt, heavy rain, fertilization, and grubbing. The combination of fertilization and heavy rain led to an increase of up to 2,700 ppb in the subsoil.