1. Institute of Soil, Fertilizer and Environmental Resources, Key Laboratory of Black Soil Protection and Utilization, Ministry of Agriculture and Rural Affairs, Harbin 150086, China
2. Institute of Plant Nutrition and Environmental Resources, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
3. Soybean Research Institute of Heilongjiang Academy of Agricultural Sciences, Harbin 150086, China
4. College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China
Abstract：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.
Key words：Black soil; Combined application of organic and inorganic fertilizers; Dissolved organic carbon; Three-dimensional fluorescence spectroscopy
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