化学氮肥有机替代条件下黑土DOC荧光光谱特征

有机无机肥配施是实现土壤培肥、减少无机肥施用的有效措施。为探讨黑土区有机肥替代无机肥(氮肥)对土壤溶解性有机碳（DOC）含量及结构的影响，本研究采用有机肥不同比例替代化学氮肥，分析土壤DOC的含量及荧光光谱特征。结果表明，M(100%有机替代化学氮肥)处理土壤DOC显著高于其他处理，其含量为325.97 mg·kg-1。与CK(不施肥)处理相比，各施肥处理荧光峰各波长均有不同程度蓝移，各处理土壤DOC的荧光指数(FI)分布在1.54~1.59范围内，腐殖化指数(HIX)均小于0.85，表明DOC来源受自生源和陆生源共同作用的影响，土壤腐质化程度均较低。平行因子分析法分析识别出3个荧光组分，分别为2个腐殖质类组分（富里酸类物质和腐殖酸类物质) 及1个类蛋白组分(类酪氨酸蛋白质物质)。各施肥处理3个组分荧光强度均高于CK处理，其中M和M₂N₂(25%有机替代化学氮肥)处理下土壤DOC总荧光强度较高，C3组分荧光强度以M₂N₂处理最高，土壤DOC中3个有机组分的相对比重以荧光组分C1最高，接近50%，表明该地区土壤中小分子物质占有较大比例，施肥能够提高土壤腐质化程度，有利于土壤DOC固定，合理的有机肥配施化学氮肥能增加DOC的有效性，提升土壤供肥能力。

Fluorescence Spectrum Characteristics of DOC in Black Soil Under Organic Substitution of Chemical Nitrogen Fertilizer

The combined application of organic and inorganic fertilizer is an effective measure to improve soil fertility and reduce the application of inorganic fertilizer. In order to investigate the effect of organic fertilizer instead of inorganic fertilizer (nitrogen fertilizer) on the content and structure of DOC in black soil area, different proportions of organic fertilizer instead of chemical nitrogen fertilizer were used to analyze the content and fluorescence spectrum characteristics of DOC. The results showed that the content of DOC in M treatment was 325.97 mg·kg-1, which was significantly higher than that in other treatments. Compared with CK treatment, the fluorescence peak wavelength of each fertilization treatment decreased to different degrees. DOC’s fluorescence index (FI) ranged from 1.54 to 1.59, and the humification index (Hix) of DOC in all treatments was less than 0.85, indicating that soil DOC was affected by both authigenic and terrestrial sources, and the degree of soil humification was low. A parallel factor analysis identified three fluorescent components: two humus components (fulvic acid like substance and humic acid like substances) and one protein like component (tyrosine like protein substance). The fluorescence intensity of the three components in each fertilization treatment was higher than that in the CK treatment. Among them, the total fluorescence intensity of soil DOC under M and M₂N₂ treatments were higher, and the fluorescence intensity of the C3 component under M₂N₂ treatment was the highest. The relative proportion of three organic components in soil DOC was the highest in C1(close to 50%), indicating that small molecular substances accounted for a large proportion in the soil. The application of fertilizer can improve the degree of soil humification, which was conducive to the fixation of soil DOC. And the reasonable application of organic fertilizer combined with chemical nitrogen fertilizer can increase the availability of DOC and improve the ability of soil fertilizer supply.