NH3 soil and soil surface gas measurements in a triticale wheat field

We present a new approach for a continuous determination of NH3 concentration in the open pore space of the soil and on the soil surface. In a semi-permeable membrane of 0.5 m length a flow of 0.5 s1pm maintained. In the tube the NH3 concentration adjusts itself to the surrounding air concentration by diffusion through the membrane. Continuous measurements have been performed in a triticale wheat field over a period of several weeks in a field experiment at Bellheim (FRG) during June and July 1995 within the frame of the European program EXAMINE (Exchange of Atmospheric Ammonia with European Ecosystems). Soil concentrations are generally below the detection limit of 0.1 μg m-3. We conclude, that the investigated soil is generally a sink for NH3. The NH3 concentration on the soil surface shows a diurnal variation due to a combination of physico-chemical desorption and adsorption phenomena associated with changes in wetness of the surrounding surfaces and the NH3 concentration in the canopy.