Contributions Of Nitrification & Denitrification To Emission Of Nitrous Oxide In Farmland Soil

Soil is the most important source of the N₂O. Nitrification and denitrification are the two uppermost micrological processes for the emission of nitrous oxide in soil, but they have tremendous difference in the contributions to the emission of nitrous oxide. The major factors influencing the emission process of nitrous oxide in soil include soil water content, soil temperature,soil NH)4⁺-N and NO₃^--N content, soil organic matter content and soil pH, etc. It is of great importance to estimate and predict the nitrous oxide flux that distinguishing the source of the N₂O via nitrification and denitrification and understanding how the change of environmental factors affects the emission of nitrous oxide.This paper mainly studies the emission process of nitrous oxide via nitrification and denitrification in the five kinds of soils, and the effect of environmental factors on the emisson process of nitrous oxide.Here the dry farmland soil is taken as the the research object and the acetylene inhibition technique and the oxygen inhibition technique as experimental methods ( the acetylene to inhibit the autotrophic nitrification,the pure oxygen to inhibit the denitrification) .The experiments include two parts:one is the N₂O seasonal emission experiments with the soil in five experimental stations; the other is the emission process of nitrous oxide via nitrification and denitrification with the environmental factors controlled. The factors include the soil temperature, the soil water content, the mineral nitrogen(NO₃^-,NH₄⁺)content, the phosphorus-to-nitrogen ratio(P/N) in the additional matter,the additional organic matter content.In the first part,the incubation experiments were conducted with soils collected from the five stations (Sanjiang, Shenyang,Fengqiu,Yanting and Jiangdu) ,then the N₂O emission rate,the contribution ratio of nitrification and denitrification to nitrous oxide emission, the seasonal fluctuations of nitrous oxide transformation ratios and the relationships between transformation ratios and the envirmental factors are elicited.In the second part, the incubation experiments were conducted with soil collected from Jiangdu under the conditions of that the single factor is controlled.Then the N₂O emission rate,the contribution ratio of nitrification and denitrification to nitrous oxide emission, the N₂O conversion ratios and the functions of the influencing factors on the N₂O conversion ratios are elicited.The experiment of the results and the conclusions are shown as follows:...