施加有机肥对农田有机质和氮素演化影响的光谱学分析

施用有机肥是改善土壤物理结构、提升土壤肥力、调控养分平衡的的有效手段之一，但目前有机肥施用对农田有机质和氮素演化的影响尚不清楚。研究了施入有机肥后土壤总有机碳(TOC)、可溶性有机碳(DOC)、无机氮含量的变化特征，并利用三维荧光光谱分析了施加有机肥后土壤DOM光谱学特性的变化规律，结合PARAFAC分析法分析了施加有机肥后不同时期土壤水溶性有机物(DOM)各组分相对含量的变化，利用2D-COS技术分析各荧光组分随时间的变化顺序，此外采用典型相关度分析法研究了DOM各组分相对含量与土壤氮素的响应关系，以探究施入有机肥对土壤有机质和氮素演变的影响。结果表明：①施加有机肥提高了土壤总有机碳、水溶性有机碳和硝态氮含量，降低了铵态氮含量；②土壤DOM三维荧光光谱图出现了A峰（UV类腐殖酸）、M峰（UVA类腐殖酸）、T峰（类色氨酸），PARAFAC分析结果显示试验土壤DOM主要由陆地源类腐殖酸（C1）、典型类腐殖酸(C2)、类色氨酸(C3)组成。结果还显示，施加有机肥能提高土壤C1，C2和C3组分的相对含量，试验期间，施加有机肥处理后土壤C1，C2和C3组分的相对含量均呈现先上升后下降的趋势，第30 d达到最大值，不同荧光组分随时间的变动顺序一般表现为C1和C2组分先增加，然后C1和C2组合降解促进C3形成，为简便起见，可用C1(C2)↑→C3来描述。类腐殖酸变动幅度较大，施加有机肥对类腐殖酸促进作用更为显著；③施加有机肥能提高土壤的生物可利用性，降低土壤腐殖化程度。试验期间，施加有机肥后BIX值呈先上升后下降的趋势，在第30 d达到最大值；HIX值呈先下降后上升的趋势，在第30 d达到最小值。BIX和HIX呈显著负相关（R2=0.732）；④C1，C2和C3相对含量与硝态氮呈正相关，与铵态氮呈负相关，且C1和C2组分的相对含量对硝态氮和铵态氮含量的影响较大。综上所述，合理施加有机肥可调控土壤有机质和氮素转化，减少农田面源污染。

Spectral Analysis of the Effect of Organic Fertilizer Application on the Evolution of Organic Matter and Nitrogen in Farmaland

Organic fertilizer is an effective means to improve soil physical structure, enhance soil fertility and regulate nutrient balance. However, the effects of organic fertilizer application on the evolution of organic matter and nitrogen in farmland are still unclear. This paper studied the changes of TOC, DOC and inorganic nitrogen contents in soil after applying organic fertilizer. The changes of DOM spectral characteristics of soil after applying organic fertilizer were analyzed using three-dimensional fluorescence spectroscopy. PARAFAC was used to analyze the changes in the relative contents of the fluorescent components in soil DOM in different periods after applying organic fertilizer, and 2D-COS was used to analyze the change sequence of the fluorescent components with time. In addition, the response relationship between the relative content of DOM components and soil nitrogen was studied using the typical correlation analysis method to explore the effects of organic fertilizer application on the evolution of soil organic matter and nitrogen. The results showed that: ① The application of organic fertilizer increased the content of total organic carbon, water-soluble organic carbon and nitrate nitrogen but decreased the content of ammonium nitrogen. ②Three-dimensional fluorescence spectra of soil DOM showed a peak (UV humic acid), M peak (UVA humic acid) and T peak (tryptophan). PARAFAC analysis showed that soil DOM was mainly composed of terrestrial humic acid (C1), typical humic acid (C2) and tryptophan (C3). The results showed that applying organic fertilizer could increase the relative contents of soil C1, C2 and C3 components. The relative contents of C1, C2 and C3 in the soil treated with organic fertilizer increased initially and then decreased, reaching the maximum on the 30th day. The change order of different fluorescence components with time was C1(C2)↑→C3, and humic acid-like changed greatly, and the promotion of humic acid-like by organic fertilizer was significant.③The application of organic fertilizer can improve the bioavailability of soil and reduce the degree of soil humification. BIX value increased first and then decreased after applying organic fertilizer and reached the maximum on the 30th day; The HIX value decreased at first and then went up and reached the minimum on the 30th day. BIX and HIX were negatively correlated (R2=0.732). ④The relative contents of C1, C2 and C3 were positively correlated with nitrate nitrogen and negatively correlated with ammonium nitrogen, and the relative contents of C1 and C2 had a great influence on the contents of nitrate nitrogen and ammonium nitrogen. In conclusion, reasonable application of organic fertilizer can control the transformation of soil organic matter and nitrogen reducing the non-point source pollution of chemical fertilizer.