土壤团聚结构上水溶性有机物的性质及其对有机肥的响应

Dissolved Organic Matter (DOM) Properties in Different Aggregates Structure and Their Responses to Organic Amendments

【目的】研究有机肥和无机肥施用后水溶性有机物(DOM)的性质及与团聚体保护的关系,揭示有机碳稳定性机制。【方法】以不同有机肥施用制度(有机肥种类、数量和施用时间)的稻田长期定位试验土壤为研究对象,通过湿筛分组获得不同团聚结构位置的水溶性有机物,测定DOM中的碳水化合物(CHC)和酚类物质(PEC)浓度。【结果】与游离组分及原土微团聚体相比,大团聚体包裹的微团聚体之间的CHC和PEC浓度更高,平均值分别为163.8和38.6 mg C.kg-1,并具有高CHC/PEC比(4.27)。与单纯施用化肥相比,施用有机肥显著提高了CHC和PEC在各团聚结构位置上的浓度,增幅分别达10.3%和6.3%,且大团聚体内微团聚体之间的位置对有机肥的响应更灵敏。基于团聚体对有机碳的保护程度,有机肥作用下大团聚体保护的CHC和PEC含量和比例均最高,而降低了原土微团聚体保护的CHC和PEC的含量和比例。【结论】不同团聚结构位置上DOM空间分布差异明显,既说明大团聚体是土壤活性有机碳增加和物理保护的最重要结构,又暗示DOM可能对大团聚体及其内部微团聚体的形成具有重要影响。CHC和PEC的浓度及二者比例均在有机肥作用下显著提高。结合团聚体分组进行DOM的评价有助于了解有机碳稳定机制及农业措施对土壤有机碳稳定性的影响。

[Objective] The interactions between dissolved organic matter （DOM） and aggregate structure were investigated with soil after organic and inorganic amendments. This study would not only help optimize fertilization managements but also provide mechanistic understanding of organic carbon stabilization. [Method] Soil samples were collected from long-term rice paddy field including fertilization treatments of the quantity, quality and the time of organic amendments. The DOM solution located in various aggregate structure was obtained by wet-sieving physical fractionation method, and carbohydrate （CHC） and phenolics （PEC） were determined as DOM properties. [Result] Compared to free fractions and original microaggregates, higher CHC （163.8 mg C.kg-1） and PEC （38.6 nag C.kg-1） as well as CHC/PEC ratio （4.27） were observed in the position of inter-microaggregates in macroaggregates. Regardless of aggregate structure, organic amendments increased the CHC and PEC concentrations by 10.3% and 6.3% than that of treatment with only chemical fertilizer, respectively. But the position of inter-microaggregates in macroaggregate showed more sensitive to organic amendments than other positions. Based on the extent of protection exerted by aggregate structure,the contents and proportions of CHC and PEC protected by macroaggregates were the highest, while those in free microaggregates outside of macroaggregates were the lowest. [ Conclusion ] Spatial heterogeneity of DOM distribution demonstrated DOM preferred accumulation at inter-miaroaggregates of macroaggregates, which have a great significance in respect to macroaggregate stability and the formation of interior microaggregate. Organic amendments increased CHC and PEC and modified their ratio. Combining aggregate and DOM fractionation would help understand the physical mechanism of organic carbon stabilization as well as the impacts of agricultural managements.