长期不同施肥的棕壤胶体凝聚动力学比较

Comparative Study on Colloidal Aggregation Kinetics of Brown Earth under Long-term Fertilization

土壤胶体的凝聚与土壤团聚体的形成密切相关。施肥改变土壤溶液环境,对土壤团聚体形成、土壤结构和土壤物质组成产生影响。探索长期不同施肥影响土壤胶体微观性质和相互作用进而影响土壤宏观现象的关联十分必要。依托35年棕壤长期定位施肥监测试验站,选取不施肥处理(CK)、施用氮肥(N)、施用有机肥(M)、氮肥与有机肥配合施用(N+M)四种处理的棕壤为研究对象,采用动态光散射技术监测不同施肥处理的棕壤胶体凝聚动力学过程,通过对比分析棕壤有机质含量、表面化学性质和棕壤矿物组成等探究不同施肥处理对棕壤胶体凝聚过程的影响。研究发现:四种长期不同施肥处理的棕壤胶体凝聚特征均表现为在低电解质浓度条件下发生慢速凝聚(RLCA)与高电解质浓度条件下的快速凝聚(DLCA);不同施肥处理胶体在相同电解质体系中的临界聚沉浓度的大小顺序均为M>N+M>CK>N。有机肥的长期施用增加了棕壤有机质含量,从而提高了胶体颗粒表面电场强度,加大了胶体颗粒间的静电斥力,加之有机质组分的空间位阻效应使得胶体的凝聚现象减弱;另一方面,长期不同施肥处理并未改变棕壤黏土矿物组成类型,但对其相对含量产生影响:其中,有机肥的长期施入使2︰1型伊利石的相对含量增加,1︰1型高岭石的相对含量减少,长期施用氮肥使伊利石相对含量减少而高岭石相对含量增加。综上,长期不同施肥处理会改变棕壤胶体的基本理化性质和矿物组成比例关系,进而影响棕壤胶体的凝聚动力学过程。

【Objective】The aggregation of soil colloids is closely related to the formation of soil aggregates.Fertilization can change the environment of soil solution,and affect the formation of soil aggregates,soil structure and soil mineral composition.It is necessary to explore the relationship between the long-term effects of different fertilization on the microscopic properties and interactions of soil colloids and thus the macroscopic phenomena of soils.【Method】Based on a 35-year long-term fertilization monitoring experiment in the experimental station of brown earth,soils treated with no fertilization(CK),nitrogen fertilizer(N),organic fertilizer(M)and the combination of nitrogen fertilizer and organic fertilizer(N+M)were selected as the research objects in this study.Dynamic light scattering technology was used to monitor the dynamic aggregation process of soil colloids with different fertilization treatments.The effects of fertilization treatments on colloid aggregation were comparatively analyzed through the organic matter content,soil mineral composition and surface chemical properties.【Result】The soil colloids of the four treatments showed the characteristics of slow aggregation(RLCA)at low electrolyte concentration and fast aggregation(DLCA)at high electrolyte concentration.The order of critical coagulation concentration of four different fertilization treatments was M>N+M>CK>N.Also the long-term application of organic fertilizer increased soil organic matter,thereby increasing the electric field strength near the surface of colloidal particles and the electrostatic repulsion between colloidal particles.Furthermore,the steric hindrance effects of humus weakened the phenomenon of colloid aggregation;On the other hand,long-term fertilization did not change the soil clay mineral composition type,but had an impact on its relative content.The application of organic fertilizer increased the relative content of 2︰1 type illite and decreased the relative content of 1︰1 type kaolinite.The application of nitrogen fertilizer reduced the relative content of illite and increased the relative content of kaolinite.【Conclusion】Different fertilization treatments for a long time changed the basic physicochemical properties and mineral composition ratio of brown earth colloids,which in turn affected the aggregation kinetics of brown earth colloids.