Description

[Synopsis]

The effect of the depth of NO and N₂O productions in soil on their emission rates was examined by mathematical model and laboratory experiment. Firstly, a simple simulation model was prepared based on a concentration profile of soil NO and N₂O in an upland field of Andosol. By changing only the depth of these gases production in soil in this model, we obtained the results that there is a high probability to mitigate NO emission by setting the production site deeper in soil, while that the depth of N₂O production site has less effect on the emission rate.

Secondly, a laboratory experiment with soil columns was carried out to verify the model results. Each column was made of topsoil of Andosol and fertilized with ammonium sulfate at rate of 20 gN m^-2 at specific depth (0-10, 5-15 or 10-20 cm). The data indicated that NO concentration gradient near soil surface became gentler with the production depth, so that the rate of NO emission from columns fertilized at l0-20 cm depth was reduced to almost same rate from no-fertilized column and to 0.9-20 % of that from fertilized at 0-10 cm depth. Remarkable property was not observed in case of N₂O.