铁氧化物影响水稻秸秆腐解的作用特征及其机制研究

The slow rate of decomposition is the key factor which restricts the utilization of straw returning to the field. Finding a way to accelerate the process of decomposition is of great significance. It has been found that the maturity of straw composting was promoted by the addition of iron-bearing materials, while the mechanisms are not completely understood. In addition, It has been confirmed that iron oxides can catalyze the Fenton reaction and promote the Maillard reaction. However, there is still no consensus on whether they can play a facilitating role during the decomposition of straw and the influence of their different crystal forms on straw decomposition. In this proposed study, whether iron oxides can promote straw decomposition and its mechanism will be investigated. A dynamic interaction system of rice straw incubated with iron oxides and microbes will be constructed, and series simulated decomposition experiment in laboratory, which combined with nuclear magnetic resonance, enzyme analytic methods, high-throughput sequencing and X ray photoelectron spectroscopy techniques, will be performed to determine the changes of (1) the composition and chemical structure of decomposition debris and humic-like substances, (2) the activity of lignocellulose-specific degrading enzymes, (3) the evolution of straw decomposing microbial communities, and (4) iron oxides reaction behaviors during the dynamic interactions. We aim to confirm whether iron oxides can promote the decomposition of rice straw, and to reveal its biochemical mechanisms preliminarily. The results will provide a theoretical basis for the research and application of new straw decomposition promoters by using iron oxides.

腐解缓慢是制约秸秆还田的关键因素，加快腐解进程对实现秸秆高效还田利用有重要意义。已有研究发现秸秆堆体中添加含铁物料有促进腐熟的效果，但其作用机制尚不完全清楚。铁氧化物催化Fenton反应和促进美拉德反应发生已被证实，然而其在秸秆腐解过程中能否发挥促进作用及其不同晶型的作用效果尚有不同结论。本项目针对铁氧化物能否促进秸秆腐解及其机制开展深入研究。以“水稻秸秆+不同晶型铁氧化物+土著微生物”动态互作体系为研究对象，通过室内模拟腐解实验，借助高级核磁共振技术，分析腐解残体和类腐殖物质组成和化学结构的变化规律；利用酶学分析方法和高通量测序技术，分析木质纤维素特异性降解酶的活性变化规律和秸秆腐解微生物群落的演变特征；利用X射线光电子能谱技术，分析铁氧化物的反应行为；综合对比分析，探讨铁氧化物能否促进秸秆腐解，并初步揭示铁氧化物影响秸秆腐解的生物化学机制，为利用铁氧化物研发新型秸秆促腐剂提供理论依据。

腐解缓慢是制约秸秆还田的关键因素，加快腐解进程对实现秸秆高效还田利用有重要意义。铁氧化物催化Fenton反应和促进Maillard反应发生已被证实，然而其在秸秆腐解过程中能否发挥促进作用及其不同晶型的作用效果尚有不同结论。本项目针对铁氧化物能否促进秸秆腐解及其机制开展深入研究。以“水稻秸秆+非晶型水铁矿/晶型针铁矿/赤铁矿+土著微生物”动态互作体系为研究对象，通过室内模拟腐解实验，探讨铁氧化物能否促进秸秆腐解，并初步揭示铁氧化物影响秸秆腐解的生物化学机制。主要结果如下：（1）从矿化特征来看，水铁矿处理秸秆分解率最大（增幅1.74%），而分解速率无明显变化；针铁矿处理分解率无明显变化，而分解速率明显增大（增幅9.7%）；赤铁矿处理分解率最小，而分解速率最快（增幅24.8%）；针铁矿和赤铁矿处理促进半纤维素降解，水铁矿处理促进半纤维素和纤维素降解，腐解物芳香化结构增加更为明显。（2）从腐殖化特征来看，随着腐解的进行，矿化分解中间产物作为前体物质向腐殖质不断转化，针铁矿和赤铁矿处理能显著提高前体物质向胡敏酸的转化效率，增加腐殖化率（增幅6.5%~20.0%）和腐殖酸聚合度（增幅4.6%~11.3%），有利于腐殖物质的累积（增幅7.9%~13.0%）；水铁矿处理形成的胡敏酸芳香度高于对照，而针铁矿和赤铁矿处理形成的胡敏酸芳香度低于对照。（3）铁氧化物处理微生物群落丰度和多样性提高（尤其是细菌），群落物种组成变异明显；水铁矿和赤铁矿处理细菌群落组成变异较大，而针铁矿和赤铁矿处理真菌群落组成相近；纤维素酶和漆酶活性与细菌群落优势菌门Firmicutes相对丰度显著正相关，而与Proteobacteria、Actinobacteriota相对丰度显著负相关；β-葡萄糖苷酶和锰过氧化物酶活性与真菌群落优势菌属Acaulium相对丰度显著正相关，而与unclassified_f__Microascaceae和unclassified_p__Ascomycota相对丰度显著负相关，从而导致木质纤维素特异性降解酶活性在腐解过程中表现出阶段性促进或抑制作用，进而影响矿化分解和腐殖质形成转化。以上研究结果为利用铁氧化物研发新型秸秆促腐剂以提高堆肥质量和农业废物利用提供了科学依据。