Effect of Long Storage and Soil Type on the Actual Denitrification and Denitrification Capacity to N2O Formation

Abstract

Abstract The actual denitrification to N2O and denitri-fication capacity to N2O after flooding of different soil samples stored for over 25 years in air-dry conditions and fresh, air dried samples were compared in our study. Zero N2O release was observed from the stored soils but the fresh soil samples had very low actual denitrification to N2O. NO3- addition significantly increased the amount of N2O (denitrification capacity to N2O) released after flooding, which depended on the length of storage and type of soils and was much higher in stored soils. Prolonged exposure of the soils to drought conditions caused a greater decrease in the Eh value compared with the fresh soil. The total cumulative release of N2O from the stored and fresh soils was correlated with the reduced NO3- and organic C content in soils enriched with NO3-. Some soils showed the capability of N2O consumption. CO2 release depended on the length of storage and type of soils under flooding after pro-longed drought. On average, CO2 release was higher from the stored rather than fresh soils. The organic C content in the stored soils was generally lower than in the fresh soils, probably due to the storage effect. The cumulative CO2 release from the stored soils was well correlated with the organic C while no correlation was observed for the fresh soil samples.