酸性红壤菜地硝化过程氧化亚氮释放机理与调控

Nitrification activity and fluxes of nitrous oxide (N2O) from nitrification process increased with N application rate in vegetable-planting acidic red soil in Southern China. It is valuable to optimizing vegetable N nutrition while alleviating N loss based on understanding the mechanisms of soil nitrification driven by functional microorganism and soil components change. In this project, PCR-DGGE technology will be employed to study the relationship between ammonia-oxidizers numbers and diversity with N2O fluxes from nitrification process, and 15N tracers used to study influence of "inorganic nitrogen fixation effection" caused by biochar application on N2O fluxes from nitrification process. Meanwhile, multivariate statistical analysis will be applied to further study the mechanism of N2O fluxes from nitrification process driven by soil microbial biochemical properties (nitrification activity and ammonia oxidation potential), soil chemical properties (pH, EC and CEC), and soil enzyme activity (urase and prolease) etc, which could provide scientific basis for mitigating N2O fluxes from vegetable-planting acidic red soil with a three year work. Another aim of this project is to evaluate the effect of biochar on mitigating N2O fluxes over a two year period with specific emphasis on soil N transformation processes.

南方酸性红壤菜地长期大量氮投入造成土壤硝化活性增强、硝化过程N2O释放比例增加，深入探讨红壤菜地硝化活性系统组分变化及其驱动机制具有改善蔬菜氮素营养和减少氮素损失双重效应。利用PCR-DGGE技术研究酸性红壤菜地氨氧化功能菌群数量、多样性及其与硝化过程N2O释放的关系，利用15N示踪技术研究生物炭添加的"无机氮固定"效应及其对硝化过程N2O释放的影响；在此基础上，综合土壤生化特征（硝化势、氨氧化潜势）、土壤化学变化（pH、EC、CEC）、土壤酶活性（脲酶、蛋白酶）等动态指标，通过多元统计分析，揭示土壤组分变化驱动硝化过程产生N2O的根源性机制，为酸性菜地土壤N2O减排工作提供科学基础。同时通过2年的田间试验探讨生物炭技术对酸性红壤菜地氮素转化的调控作用及其在减少硝化过程N2O释放方面的应用前景。

南方酸性菜地土壤长期大量氮投入造成土壤硝化活性增强、硝化过程N2O释放比例增加。对硝化作用强度、N2O释放、氨氧化功能菌群多样性等进行了研究，揭示土壤组分变化驱动硝化过程产生N2O的作用机制。结果表明：强酸性土壤（I号，pH4.03）NH4+-N和NO3--N变化平缓。酸性土壤（II~IV号，pH 4.81~6.02）不加NH4+条件下净硝化作用为一级反应方程，加NH4+后净硝化速率增加一个数量级。不加NH4+和加NH4+条件下土壤N2O释放顺序均为I > II > IV > III。上述土壤加入(15NH4)2SO4标记液培养7d。硝化速率分别为0.52、7.01、11.6和6.05 mg•kg-1•d-1。15N2O-N释放量分别为6.19、66.0、50.9和41.1µg•kg-1。硝化产生的15N2O占总15N2O的比例分别为0.27、0.23、0.05和0.05。硝化过程释放的15N2O分别为1.80、27.1、11.6和2.97µg•kg-1。导致酸性土壤具有较强硝化活性的主要微生物可能是氨氧化细菌（AOB）。II、III号土壤AOB 的T-RFs 296的相对丰度分别为76.9%和73.0%，基因种群相对单一化。培养条件下鲜猪粪配施无机肥的N2O释放量显著低于纯化肥处理，田间条件下猪粪堆肥配施无机肥的N2O释放量显著低于纯化肥处理。盆栽条件下生物炭显著降低土壤N2O释放，土壤NH4+-N是影响土壤N2O排放最主要的因素。15NO3--N随生物炭用量的增加显著降低，10~20%生物炭处理的初级硝化速率低于对照和5%生物炭处理。研究结果表明酸性土壤中来自硝化过程释放的N2O不容忽视，硝化速率和硝化过程15N2O释放量最高的土壤优势AOB种群（T-RFs 296）富集。生物炭具有硝化抑制剂的功能，可以在酸性高肥力土壤中使用。.