Abstract：The application of organic fertilizer is an effective way to improve the quality and efficiency of crop production. Studying the distribution of dissolved organic matter (DOM) in soil profiles under the application of organic fertilizer from different sources is helpful to optimize the utilization of organic fertilizer and further understand the environmental behavior of DOM. In this paper, 2D correlation spectroscopy (2D-COS) was used to study the effects of different organic fertilizers (pig manure, chicken manure, sheep manure, cow manure and biogas residue) on DOM distribution in soil profile. The results showed that the relative content and composition of DOM in soil were mainly affected by organic fertilizer return to field. After applying different organic fertilizers, the relative content of DOM in soil was always higher than that in control (CK) treatment, and the relative content of DOM in 0-10 cm soil layer had the greatest effect, with an average increase of 14.67 g·kg-1. Different types of organic fertilizer had a certain difference in the increase of profile DOM, among which chicken manure organic fertilizer had the greatest effect on the increase of profile DOM, increasing by 21.42%. The application of organic fertilizer mainly increased the relative content of tyrosine-like components (C4), and had the greatest impact on the relative content of C4 in 10-20 cm soil layer, with an average increase of 4.12%, in which sheep manure and biogas residue had the greatest impact, with an increase of 7.80% and 7.89%, respectively. 2D-COS analysis showed that the application of organic fertilizer from different sources had the greatest impact on dissolved microbial metabolites and protein-like components (295 nm, 315 nm), CK and chicken manure treatment mainly affected dissolved microbial metabolites, and other treatments first responded to protein-like components. The humification index HIX, Fn(330) and Fn(280) decreased with the increase of soil depth, but the changes of HIX, Fn(330) and Fn(280) were different with different types of organic fertilizer, among which cow manure had the greatest effect on HIX and Fn(330). Sheep manure had the greatest effect on Fn(280). The biological index BIX and freshness index β∶α increased with the increase of soil depth, and the influence of biogas residue was the most significant, but the fluorescence index FI had no significant change.
