Gaseous Nitrogen Emissions and Mineral Nitrogen Transformations as Affected by Reclaimed Effluent Application

Irrigation with reclaimed effluent (RE) is essential in arid and semiarid regions. Reclaimed effluent has the potential to stimulate gaseous N losses and affect other soil N processes. No direct measurements of the N 2 and N 2 O emissions from Mediterranean soils have been conducted so far. We used the 15 N gas flux method in a field and a laboratory experiment to study the effect of RE irrigation on gaseous N losses and other N transformations in a Grumosol (Chromoxerert) soil. The fluxes of N 2 , N 2 O, and NH 3 were measured from six Grumosol lysimeters following application of either fresh water or RE. The N fertilizer was applied either as 15 NH 4 or 15 NO 3 Only up to 0.3% from the applied N fertilizer was lost as N 2 O + NH 3 Reclaimed effluent enhanced the losses of NH 3 , but did not affect those of N 2 O. Nitrification and denitrification were equally important to N 2 O production. Laboratory incubations were performed to both confirm the influence of the irrigation water type and to test the effect of moisture content. Significant quantities of N 2 and N 2 O (up to 3.1% of the applied fertilizer) were emitted from saturated soils. Reclaimed effluent application did not induce higher N 2 O emissions, yet significantly more (approximately 33%) N 2 was emitted from RE‐irrigated soils. Denitrification contributed up to 75% of the N 2 O amounts emitted from saturated soils. Reclaimed effluent application inhibited nitrification in the Grumosol by 15 to 25% and induced NO 2 accumulation in soils incubated at a field‐capacity moisture content.