有机肥DOM性质影响化肥氮利用的土壤生物学机制

Organic fertilizer application plays an important role in improving nitrogen use efficiency (NUE). Currently, most of researches about the effect of organic fertilizer on NUE normally concerned in the application of different types or proportion of organic fertilizers, only a few researches focused on the impact of organic fertilizer production process. Organic fertilizers are the main sources of dissolved organic matter (DOM) in soils, and DOM is the most easily to be used by carbon source, which has a close relationship with soil’s N transition. However, the effects of DOM properties on chemical nitrogen fertilizer utilization and its soil biological mechanism are still unclear. Therefore the incubation and pot experiments are conducted through bonding with DOM, soil microorganism and soil nitrogen transformation, to study the behaviour of DOM on soil N supply, changes of soil microbial biomass nitrogen, and plant N uptake, as well as the DOM’s effect on relevant enzyme of N transformation and the form and function of the microorganisms. During the experiments, 15N tracer technique, spectrometry, and molecular biology methods would be used. Finally, the mechanism action of DOM’s role on chemical N fertilizer supply, N transformation, and N uptake through influencing the soil biological characteristics would be evaluated to reveal the effects of DOM properties of organic fertilizer on chemical nitrogen fertilizer utilization and its soil biological mechanism. Meanwhile, the study would provide the scientific basis for decisions regarding the recycle of solid waste, and the rational utilization of organic fertilizer, as well as the sustainable development of agriculture.

配施有机肥是提高氮肥利用的重要手段。国内外的研究主要关注不同种类和不同配施比例有机肥对氮利用的影响，很少关注有机肥生产过程（堆肥化）与氮利用的关系。有机肥是土壤水溶性有机物（DOM）重要来源，DOM是土壤微生物最易利用的碳源，与土壤氮转化关系密切，但有机肥中DOM影响化肥氮利用的作用及其土壤生物学机制尚不清楚。本研究通过盆栽和培养试验，利用15N示踪技术，结合光谱法和分子生物学手段，以“DOM-微生物-氮转化”为纽带，系统地研究有机肥DOM对土壤氮供应特征、土壤微生物氮库容量变化、作物化肥氮吸收、土壤DOM性质以及氮转化相关酶、微生物组成、功能的影响；明确DOM协调化肥氮的供应和吸收利用的作用机理和DOM介导的土壤生物学特性对土壤氮转化和化肥氮吸收利用的影响机理，揭示有机肥DOM影响化肥氮利用土壤生物学机制。为促进固体废弃物资源化、有机肥合理利用和农业可持续发展提供科学依据。

本研究基于堆肥的DOM性质变化与堆肥腐熟程度的关系，以“DOM-微生物-氮转化”为纽带，探究有机肥中DOM对化肥氮吸收利用的影响；结合土壤氮供应特征、土壤微生物氮库容量变化特征、土壤氮转化和关键微生物过程，揭示有机肥DOM性质影响化肥氮利用的土壤生物学机制。结果表明，氮肥利用率与有机肥腐熟程度呈正相关，当GI≥80%时，差异不显著（P>0.05）；有机肥DOM的加富和去除对氮肥利用率有显著的影响；微生物氮库容量是影响化肥15N吸收利用的关键驱动因子。不同腐熟度有机肥DOM对土壤标记态铵态氮、标记态微生物量氮、脲酶、蛋白酶活性以及土壤细菌、氮转化关键微生物丰度的影响总体表现为：无机肥+加富DOM有机肥处理＞无机肥+正常有机肥处理＞无机肥+去除DOM有机肥处理；GI值为80%的有机肥或GI值为100%的有机肥＞GI值为50%的有机肥。ABT分析结果表明：标记态微生物量氮的增加是提高化肥15N利用率的重要因素。多元逐步回归分析与结构方程模型表明：有机肥DOM的添加，增加了土壤DOC含量，提高了土壤细菌数，促进土壤微生物对铵态氮的固持，对标记态微生物氮的增加起到正向作用；而氨氧化细菌受土壤铵态氮的影响较大，氨氧化细菌丰度的提升可能会促进土壤氨氧化过程，增加土壤无机氮含量，为提高化肥15N吸收利用提供了一定的底物；土壤硝态氮对氧化亚氮还原酶的影响较大，其丰度的提高可能会促进土壤反硝化进程。因此，有机肥DOM更利于促进土壤微生物对15NH4+-N的固持，增加土壤MB15N容量，减少氮肥的损失，从而提高化肥氮的利用效率。. 本项目以“DOM-微生物氮转化”为纽带，揭示有机肥DOM性质影响化肥利用的土壤生物学机制，对进一步阐明合理配施有机肥提高化肥氮利用率的作用机理，为“化肥零增长”和“有机替代”提供良好的理论支撑，具有理论意义。研究明确了不同腐熟程度有机肥的DOM性质对化肥氮吸收利用影响的作用和意义，对我国有机固体废弃物资源化利用和有机肥的生产与应用有重要的指导作用，具有现实意义。