Nitrous Oxide Emission From A Long-term Fertilized Black Soil

One normal laboratory incubation and two laboratory incubations with gas inhibition method and substrate regulation method were conducted to investigate N₂O emission and production of the black soil from the Key Observation Station of the Harbin Black Soil Ecology of Harbin city, Heilongjiang province, China.After 24 hours incubation, soil emitted the highest N₂O in the treatment of single application of chemical fertilizer or manure. N₂O emission peak value decreased with the increase of single application amount of fertilizer nitrogen or phosphorus, however, cumulative N₂O emission increased with the increase of single application amount of fertilizer nitrogen, and the results showed that excessive fertilizer nitrogen had a short-term inhibition, but as the incubation time going, soil microorganism could utilize it to generate massive N₂O. N₂O emission increased with the increase of the manure application. When compared with combined fertilizer N-P, the treatment of combined manure and fertilizer N-P postponed the emergence of N₂O emission peak, and the lagging time increased with the increase of combined application amount. On the basis of normal manure application, combined fertilizers applied to the soil could significantly boost N₂O emission.The availability of O₂ in soil is one of the main factors regulating nitrification, denitrification and the release of N₂O. The main process of N₂O production in the treatment of pure oxygen was heterotrophic nitrification, while in both of the treatments with air and argon, denitrification was the predominant process of N₂O generation, and the greatest N₂O emission was observed in anaerobic treatment. Denitrifying capacity was the greatest in the long-term fertilized black soil, and the following was heterotrophic nitrifying capacity, and the lowest one was autotrophic nitrifying capacity.N₂O emission increased sharply after the addition of low molecular weight organic substances. Heterotrophic nitrification was the main process in the treatment of citric acid, and the treatment of substrate ammonium emitted higher N₂O than the treatment of substrate nitrate, indicating that the heterotrophic nitrifying capacity was greater in the treatment of substrate ammonium and citric acid. Compared with the treatment of substrate ammonium, the treatment of substrate nitrate had a greater denitrifying capacity, and low molecular weight organic substances could significantly accelerate the transformation of NO₃^--N, and the contribution of denitrification of citric acid to N₂O production was lower than glucose and alanine. Not only as the carbon and energy source of microorganism, alanine can also be used as the nitrogen source, therefore, alanine had a great positive impact on N₂O emission.