氮肥品种和含水量对水稻土N2O排放速率及排放过程的影响

稻田是全球重要的N_2O排放源,氮肥有效性和水分状况是影响稻田N_2O排放的关键因素。为探明水稻土在施用尿素和硫酸铵时,水分变化对短时间内N_2O总排放速率及不同硝化过程(自养硝化、异养硝化、非生物作用)贡献的影响,通过室内培养实验,采用乙炔抑制法,测定了不同时间段N_2O释放量,并计算释放速率。结果表明:施用氮肥可以显著提高自养硝化、异养硝化及总过程的N_2O排放速率,并且施尿素处理N_2O排放速率大于施硫酸铵。随着土壤水分含量由48%增加至160%,总N_2O排放速率以及自养硝化、异养硝化N_2O排放速率显著增加。供试水稻土N_2O的产生主要是由生物过程主导的,其中硝化作用(包括自养硝化、异养硝化)最高贡献达51.1%,非生物作用贡献所占比重很小。这些结果可为科学施肥,降低农田土壤N_2O排放提供科学依据。

Effects of nitrogen fertilization and water content on the process and rate of N2O emission in paddy soils

Paddy soil is an important source of N₂O emission, and nitrogen availability and soil moisture are the key factors affecting the emission of N₂O. The influence of nitrogen form (urea and ammonium sulfate) and water content on the attribution of autotrophic, heterotrophic, and abiotic nitrification to N₂O emission from the paddy soil was investigated under simulated conditions by using the acetylene inhibition method to measure the N₂O emission rate at different stages. The results showed that the nitrogen fertilizer significantly increased the rate of N₂O emission by autotrophic and heterotrophic nitrification processes and the total process. The N₂O emission of the soil treated with urea was higher than that of the soil treated with ammonium sulfate. With the soil moisture content ranging from 48% to 160%, the total N₂O emissions and the amount of N₂O emitted by autotrophic and heterotrophic nitrification processes increased significantly. The production of N₂O is mainly dominated by the biological processes. The highest contribution of the biological nitrification process (including autotrophic and heterotrophic nitrification) reached 51.1%, but the contribution of abiotic nitrification was relatively less. These results provide a scientific base for improving the nitrogen-use efficiency of rice plants and for reducing the agricultural greenhouse-gas emission in paddy soils.