基于紫外-可见光光谱法研究长期不同施肥对砖红壤溶解性有机质化学性质的影响

溶解性有机质（DOM）是土壤中最为活跃的一部分，具有重要的生态环境意义。明确不同施肥方式对DOM化学性质的影响，可为土壤肥力管理提供依据。因此，该试验以连续四年的不同施肥管理为基础，结合紫外-可见吸收光谱，探求不同施肥方式下，土壤中溶解性有机质的含量和化学性质的变化情况。试验共设置4个处理：CK（不施肥）；CF（化肥）；OG（有机肥）；ST（秸秆）。结果表明，与CK组相比，OG和ST的DOC(溶解性有机碳)含量为95.97和104.89 mg·kg-1，分别是CK组的129%和141%。相反，CF的DOC含量为15.32 mg·kg-1，仅为CK组的21%。OG显著提高了有色溶解性有机质[CDOM，以α（355）表征]含量，是CK组的2.76倍，ST无明显变化；CF则显著降低CDOM含量，仅为CK组的0.55倍。施用OG导致土壤紫外吸收曲线红移，表明有机肥的施用能够提高土壤DOM的共轭双键物质含量和腐殖化程度；与CK相比，OG中DOM的芳香性、疏水性、腐殖化程度的特征常数SUVA₂₅₄，SUVA₂₆₀和SUVA₂₈₀增大，揭示了有机肥的施用能够提高DOM的芳香性、疏水性组分以及腐殖化程度，秸秆处理增加不明显。施用化肥则出现明显降低。吸光度比值A₂₅₀/A₃₅₄，相比CK，CF显著增加，表明施用化肥使DOM分子变小，OG和ST处理无明显变化；秸秆施用导致A₄₆₅/A₆₆₅显著增加，表明秸秆能够有效提高DOM中蛋白质和碳水化合物含量；施用有机肥和秸秆A₃₀₀/A₄₀₀均大于3.5，表明土壤中DOM主要以富里酸为主，而施用化肥A₃₀₀/A₄₀₀明显低于3.5，表明土壤中DOM主要以胡敏酸为主。施用化肥出现S_R＞1，不施肥、有机肥、秸秆三者的S_R＜1，也表明了有机肥、秸秆能够增加分子量。有机肥和秸秆能有效增加土壤DOM含量，提升土壤肥力。尤其是施用有机肥，更能显著增加土壤DOM的共轭物质、腐殖化程度、疏水比例、芳香性以及分子量。而长期施用化肥则导致耕层土壤肥力降低。

Response of Dissolved Organic Matter Chemical Properties to Long-Term Different Fertilization in Latosol: Insight From Ultraviolet-Visible Spectroscopy

Dissolved organic matter (DOM) is the most active part of the soil, which is important ecological environment significance. It can provide a basis for soil fertilization management to clarify the impact of different fertilization methods on the chemical properties of DOM. Based on different fertilization methods for four years, this experiment is combined with UV-Visible absorption spectroscopy to explore the changes in dissolved organic matter chemical properties in soil. Four treatments were set up in the experiment: CK (non-fertilization); CF (chemical fertilization); OG (organic fertilization); ST (straw). The results show that, compared with the CK group, the DOC content of OG and ST are 95.97 and 104.89 mg·kg-1, which are 129% and 141% of the CK group. On the contrary, the DOC content of CF is 15.32 mg·kg-1, which is 21% of the CK group. OG significantly increase the content of colored dissolved organic matter (CDOM, represented by α(355)), which is 2.76 times that of the CK group, and there is a change in ST inconspicuous; CF significantly reduces the CDOM content, which was only 0.55 times of the CK group. The application of OG caused redshift phenomenon in the ultraviolet absorption curve of soil, indicating the application of OG can increase the conjugated double bond substances and the degree of humification of the soil DOM; Compared with CK, the characteristic constants SUVA₂₅₄, SUVA₂₆₀, and SUVA₂₈₀ of DOM in OG were increased, revealing that the application of organic fertilization could improve the aromaticity, hydrophobic components and humification degree of DOM, the increase in straw treatment was not obvious, but the application of CF showed a significant decrease; The absorbance ratio A₂₅₀/A₃₅₄ was significantly increased compared to CK and CF, indicating that the application of chemical fertilization reduced the DOM molecule, but OG and ST treatments did not change significantly; the application of straw resulted in a significant increase in A₄₆₅/A₆₆₅, indicating that straw could effectively increase the content of protein and carbonhydrate in DOM; A₃₀₀/A₄₀₀ was greater than 3.5 under the application of OG and ST, and it showed this main soil DOM was rich in fulvic acid, while under the application of CF, A₃₀₀/A₄₀₀ was significantly lower than 3.5, showing that the main soil DOM was humic acid. Application of CF showed S_R>1, S_R<1 of CK, OG, and ST which also showed that organic fertilizer and straw could increase molecular weight. In summary, the organic fertilization and straw can effectively increase the soil DOM content and improve soil fertility; especially the application of OG, can increase the conjugated substances, humification degree, hydrophobic ratio, aromaticity and molecular weight of soil DOM. On the contrary, long-term application of CF cause the fertility of the cultivated layer reduced.