长期施肥条件下红壤有机碳化学结构与团聚体稳定性的关系

The Relationship between Chemical Structure of Organic Carbon and Stability of Aggregates in Red Soils under Long-term Fertilization

【目的】红壤普遍存在团聚体结构较差和有机碳含量较低的问题,土壤有机碳是影响土壤团聚体结构的重要指标,但以往研究主要关注有机碳含量与团聚体的相关关系,而对有机碳的化学结构如何调控团聚体结构则缺乏深入研究。【方法】依托始于1986年的红壤旱地长期施肥试验,选取不施肥(CK)、施用氮磷肥(NP)、施用氮磷钾肥(NPK)、施用氮磷钾肥和猪粪(NPKOM)和单施猪粪(OM)五个处理。于2019年早玉米收获后采集0~20 cm土壤样品,分析土壤有机碳含量、有机碳化学结构和团聚体组分等指标,并进一步量化有机碳化学结构与团聚体平均重量直径的相关关系。【结果】结果表明:NPKOM和OM处理的有机碳分别比CK增加了51.63%和34.34%。与CK相比,NPKOM处理的烷基碳、烷氧碳比例分别提高了29.85%和21.54%,OM处理的烷基碳、烷氧碳比例则分别比CK提高了31.98%和28.81%。但是,NPKOM和OM处理的芳香度分别比CK降低了24.90%和25.19%,而NPKOM和OM处理的脂族碳/芳香碳比值则分别比CK增加了64.87%和73.34%。同时,施肥处理(NP、NPK、NPKOM和OM)的团聚体平均重量直径(MWD)均显著高于CK处理。土壤有机碳和脂族碳/芳香碳比值均与MWD呈显著正相关关系,但芳香度与MWD呈显著负相关关系。【结论】有机肥施用是改善红壤旱地有机碳化学结构的重要措施,其施用提升了红壤旱地烷基碳/烷氧碳和脂族碳/芳香碳比值,降低了土壤有机碳的芳香度,从而促进了土壤有机碳的累积和团聚体平均重量直径的增加,为红壤结构稳定奠定了基础。

[Objective]In general,it is poor structure and lower organic carbon content in red soil.Soil organic carbon(SOC)is the key indicator for affecting soil structure.However,lot of studies were focused on the relationship between SOC and aggregates.It was unknown that the regulation mechanism of SOC on aggregate.[Method]Based on the long-term experiment in red soil which started in 1986.Five treatments were selected:No fertilizers(CK);mineral nitrogen and phosphorus(NP);mineral nitrogen,phosphorus,and potassium(NPK);NPK plus pig manure(NPKOM);pig manure only(OM).Soil in 0-20 cm was sampled after early corn harvested in 2019.SOC content and its chemical structure,aggregate components were measured and analyzed.The correlation between the chemical structure of SOC and aggregates was further quantified.[Result]Compared with CK,SOC content under NPKOM and OM was increased by 51.63%and 34.34%,respectively;the proportion of alkyl carbon and alkoxy carbon in NPKOM was increased by 29.85%and 21.54%,respectively;they were increased by 31.98%and 28.81%,respectively,in OM.But the proportions of aromatic carbon and carboxyl carbon in NPKOM and OM were decreased.Compared with CK,the aromaticity of NPKOM and OM was reduced than CK by 24.90%and 25.19%,respectively.While,the aliphatic carbon and aromatic carbon ratio were increased by 64.87%and 73.34%.Meanwhile,the mean weight diameter(MWD)under all the treatments with fertilizer(NP,NPK,NPKOM and OM)was significantly higher than that under CK.SOC,aliphatic carbon,and aromatic carbon ratio were positive correlated with MWD,while the aromaticity was negative correlated with MWD.[Conclusion]Manure application was an optimum management to improve SOC chemical structure.The ratio of alkyl carbon and alkoxy carbon,aliphatic carbon and aromatic carbon were increased,but the aromaticity was reduced.Therefore,the soil structure was improved by SOC accumulation and MWD promotion.