电解质添加对南亚热带赤红壤团聚体稳定性的影响

Effect of electrolytes addition on the stability of lateritic red soil aggregates in the south subtropical region

为探究外源电解质添加对南亚热带土壤团聚体稳定性的影响,以砂页岩和花岗岩2种母质发育的赤红壤为研究对象,以0、0.05、0.10、0.20、0.50和1.00 mol/L的NaCl、KCl、MgCl_(2)、CaCl_(2)溶液为介质,采用Le Bissonnais法的3种方式(快速润湿、慢速润湿和预润湿振荡)对>3.00~5.00 mm的团聚体进行处理。结果表明:1)随着电解质浓度浓度的升高,快速湿润、慢速湿润、预湿润振荡处理下的团聚体平均质量直径(MWD)均呈现出下降的趋势。MWD值在电解质浓度从0增加到0.10 mol/L的过程中快速下降,其后逐渐趋于平缓;2)电解质浓度的增大改变了团聚体的粒径分布。随着电解质浓度的升高,2种土壤团聚体>3.00~5.00 mm的粒径质量分数均降低;3)在静水条件下,团聚体稳定度在浸没于溶液中前2 min内发生剧烈变化,相较于电解质溶液,团聚体在纯水中更稳定;4)不同破碎机制下2种土壤团聚体稳定性不同。消散作用和非均匀膨胀作用下,花岗岩赤红壤团聚体的稳定性较高,机械破碎作用下相反。从相对消散指数和相对机械破碎指数来看,2种团聚体均对消散作用更加敏感。该结果表明,外源电解质添加会降低团聚体的稳定性,改变团聚体粒径分布。浸没于溶液中短时间内土壤团聚体稳定性可发生较大改变。

[Background]The southern subtropical region is an important agricultural production area in China.In this region,soil erosion and land degradation become seriously due to agricultural production,climatic conditions and other reasons.Soil quality can be influenced by exogenous electrolyte entering the soil during agricultural production and life.Aggregates are the basic units of soil structure and play an important role in maintaining soil fertility and soil structure.In this study,we investigated the effect of exogenous electrolytes on the stability of lateritic red soil aggregate developed from granite and sand shale in the southern subtropical region.[Methods]Sand shale lateritic red soil was collected from Wuming,Nanning,Guangxi and granite lateritic red soil from Longxu,Wuzhou,Guangxi.The selected study areas in both places are hilly terrain.The soil was collected from both sites in its original state and then air dried in the laboratory.The dry sieving method sieved out>3.00-5.00 mm aggregates.The aggregates of>3.00-5.00 mm of lateritic red soil developed from sand shale and granite parent material in the south subtropics were treated by three methods of Le Bissonnais method with 0,0.05,0.10,0.20,0.50 and 1.00 mol/L NaCl,KCl,MgCl_(2)and CaCl_(2)solutions as media.[Results]1)The mean weight diameter(MWD)under fast-wetting treatments(FW),slow-wetting treatments(SW),and pre-wetting shock treatments(WS)showed a decreasing trend with the increase of electrolyte concentration.MWD values decreased faster before 0.10 mol/L and slowed down thereafter.2)The particle size content of the aggregates changed with the increase of electrolyte solution concentration.When electrolyte solution concentration increased,the content of the>3.00-5.00 mm decreased.In three wetting treatments,the particle size content of granite lateritic red soil aggregates largely decreased with the decreasing of particle size,whereas the size order of the sand shale lateritic red soil aggregates was not consistent among treatments.3)In static conditions,aggregate stability(AS)changed dramatically within the first 2 min of submersion in the solution,and the AS in pure water was greater than that in the electrolyte solution.4)The stability of the 2 aggregates under different treatments was different.The stability of granite lateritic red soil aggregates was higher under dissipation and non-uniform expansion,and the opposite under mechanical crushing.The relative mechanical crushing index of both aggregates was smaller than relative shaking index,indicating that both aggregates were more sensitive to dissipative effects.[Conclusions]This study shows that electrolyte addition can reduce the stability of aggregates and change the aggregates particle size content.The stability of the aggregates can be changed significantly within a short time when submerged in solution.These results provide reference for soil improvement,soil conservation and sustainable utilization of cultivated land in the southern subtropical region.