长期不同施肥处理对黑土根际土壤有机碳结构组分的影响

土壤有机碳是农业生态系统的关键驱动和调节者，特别是根际微域有机碳动态对土壤碳素循环和矿质营养元素释放起着重要作用。研究长期不同化肥和有机肥施用下大豆根际土壤有机碳、活性有机碳以及有机碳结构的变化规律，深入了解根际有机碳固持和稳定机制，为完善农田生态系统碳固持和农田可持续发展提供科学依据和理论支撑。该研究依托黑土长期定位试验，采用化学分析、固态13C-核磁共振 (13C-NMR)等方法研究大豆根际土壤有机碳含量、活性有机碳含量和有机碳结构组分变化规律。结果表明，与非根际土壤相比，大豆根际土壤有机碳含量显著增加，长期施肥处理能够显著增加根际土壤有机碳和低活性有机碳含量，以常量有机肥加氮磷钾（MNPK）处理提升效果最好。核磁共振实验结果表明，与不施肥处理相比，MNPK处理明显增加根际土壤烷基碳、烷氧基碳比例以及烷基碳/烷氧基碳比值，降低芳香基碳和芳香碳/总碳比值，在非根际土壤中尤其显著；常量氮磷钾（NPK）处理增加芳香基碳比例和芳香碳/总碳比值，在根际土壤中烷基碳比例和烷基碳/烷氧基碳比值增加，烷氧基碳比例降低，非根际土壤测试结果相反。综上所述，MNPK处理能够显著提升根际有机碳含量，增加有机碳中烷基碳、烷氧基碳比例以及烷基碳/烷氧基碳比值，促进团聚体形成和增加土粒结构稳定性，而NPK处理增加芳香基碳比例和芳香碳/总碳比值，降低根际烷氧基碳比例，团聚体稳定性降低，同时证明固态13C-核磁共振技术结合半定量分析能够准确地分析不同有机碳结构组分变化，深刻认识根际土壤有机碳的稳定机制。

Changes in Organic Carbon Components and Structure of Black Rhizosphere Soil Under Long-Term Different Fertilization

Soil organic carbon is the crucial driver and regulator of the agricultural ecosystem. In particular, the quantification of rhizosphere organic carbon plays an important role in the soil carbon cycle and mineral nutrient release. Through the research on the changes of organic carbon, labile organic carbon and organic carbon structure in soybean rhizosphere soil under different long-term fertilization, we can further understand the mechanism of rhizosphere organic carbon fixation and stability. The outcome of this research would provide a scientific basis and theoretical support for improving carbon fixation of farmland ecosystem and sustainable development of farmland. The experiment uses a long-term black soil positioning test. Chemical analysis and 13C-NMR were used to study dynamic changes in organic carbon, labile organic carbon and organic carbon structure in soybean rhizosphere soil. The results showed that organic carbon concentrations were generally higher in rhizosphere soil than in bulk soil. Long-term fertilization treatment could significantly increase concentrations of organic carbon and low labile organic carbon in rhizosphere soil, and MNPK treatment had the best effect. Compared with CK treatment, MNPK treatment significantly increased the proportion of alkyl C, O-alkyl C and the ratios of alkyl C to O-alkyl C, and decreased aromatic C and the ratios of aromatic C to total C in rhizosphere soil, especially in bulk soil.NPK treatment increased the proportion of aromatic C and the ratios of aromatic C to total C, increased alkyl C and the ratios of alkyl C to O-alkyl C in rhizosphere soil, and decreased O-alkyl C, which the results were opposite in bulk soil. The above analysis showed that: MNPK treatment significantly increased the content of rhizosphere organic carbon, increased alkyl C, O-alkyl C and the ratios of alkyl C to O-alkyl C while promoting the formation of aggregates and increased the stability of soil particle structure. NPK treatment increased aromatic C, and the ratios of aromatic C to total C reduced the rhizosphere O-alkyl C, which decreased the stability of aggregates. At the same time, it is proved that 13C-NMR technology combined with semi-quantitative analysis could be used to comprehensively analyze the structural changes of different organic carbon functional groups to gain a deeper understanding of the stability mechanism of rhizosphere soil organic carbon.