广西甘蔗主产区土壤酸化特征分析

Acidification characteristics of soil in the main sugarcane planting areas in Guangxi

【目的】分析广西甘蔗主产区土壤pH现状和分布特点及土壤pH与交换性盐基离子含量、土壤交换性铝含量的关系,为探明广西蔗区土壤酸化机制及土壤酸化治理提供科学依据。【方法】2023年春季在广西15个甘蔗种植面积较大的县(区、市)共采集515个地块的0~20 cm土壤样品,分别采用去离子水、0.01 mol/L CaCl_(2)溶液和1 mol/L KCl溶液测定土壤pH[分别标记为pH(H_(2)O)、pH(CaCl_(2))和pH(KCl)],同时测定交换性盐基离子、交换性酸和交换性铝含量,分析土壤pH与交换性盐基离子和盐基饱和度的关系,以及交换性铝积累对土壤p H的响应。【结果】广西甘蔗主产区土壤p H(H_(2)O)平均值为4.52,其中pH(H_(2)O)<4.5的强酸性土壤占63.9%;pH(CaCl_(2))和p H(KCl)平均值分别为4.06和3.71,与pH(H_(2)O)相比分别低0.46和0.81。土壤交换性酸平均含量为4.59 cmol/kg,且>6.0 cmol/kg的土壤占比32.8%。交换性铝是交换性酸的主要组分,在交换性酸含量>4.0 cmol/kg的土壤中,交换性铝占比超过80.0%。交换性铝含量与pH(KCl)的拟合优度最高(R^(2)=0.9005),当土壤交换性铝含量为2.0cmol/kg时,其所对应的pH(H_(2)O)、pH(CaCl_(2))和pH(KCl)的平均值分别为4.67、4.07和3.66。土壤交换性钙、交换性镁和交换性钾的平均含量分别为4.67、0.42和0.49cmol/kg,土壤交换性钙含量<1.5 cmol/kg的土壤占比31.1%,交换性镁含量<0.25 cmol/kg的土壤占比31.7%,交换性钾含量以介于0.2~0.6 cmol/kg的土壤占多数,约为46.8%。土壤盐基饱和度平均为49.5%,且有15.3%的土壤盐基饱和度在20%以下。盐基饱和度、交换性钙和交换性镁含量与土壤pH(H_(2)O)、pH(CaCl_(2))和pH(KCl)均呈极显著正相关(P<0.01)。【结论】广西甘蔗主产区出现严重的土壤酸化现象,pH≤4.5的土壤占大多数。钙镁缺乏、盐基饱和度偏低和铝毒危害风险较高已成为广西甘蔗主产区土壤酸化的主要特征。

【Objective】The present situation and distribution characteristics of soil pH in the main sugarcane planting areas of Guangxi and the relationship between soil pH and exchangeable base cations contents and soil exchangeable alu‐minum content were analyzed,which provided scientific basis for exploring the mechanism of soil acidification and soil acidification control in sugarcane areas of Guangxi.【Method】In the spring of 2023,a total of 515 soil samples were col‐lected from 15 counties(districts or cities)with large sugarcane planting areas in Guangxi.The soil pH was measured using deionized water,0.01 mol/L CaCl_(2) solution and 1 mol/L KCl solution,denoted as pH(H_(2)O),pH(CaCl_(2)),and pH(KCl)respectively.Additionally,the contents of exchangeable base cations,exchangeable acids,and exchangeable alu‐minum were measured.The relationship between soil pH and exchangeable base cations and the relationship between soil pH and base saturation were analyzed,and the response of exchangeable aluminum accumulation to soil pH was also ana‐lyzed.【Result】The average soil pH(H_(2)O)in the main sugarcane planting areas of Guangxi was 4.52,and strongly acidic soil with pH(H_(2)O)<4.5 accounted for 63.9%.The average values of pH(CaCl_(2))and pH(KCl)were 4.06 and 3.71 re‐spectively,which were 0.46 and 0.81 lower compared to pH(H_(2)O).The average content of soil exchangeable acid was 4.59 cmol/kg,and soil with exchangeable acid>6.0 cmol/kg accounted for 32.8%.In exchangeable acids,exchangeable aluminum was the dominant component.In soils with exchangeable acids content>4.0 cmol/kg,the proportion of ex‐changeable aluminum exceeded 80.0%.The equation fitted with pH(KCl)and soil exchangeable aluminum content had the highest goodness fit(R^(2)=0.9005).When the soil exchangeable aluminumcontent was 2.0 cmol/kg,the corresponding average values for pH(H_(2)O),pH(CaCl_(2)),and pH(KCl)were 4.67,4.07,and 3.66 respectively.The average contents of exchangeable calcium,exchangeable magnesium and exchangeable potassium in the soil were 4.67,0.42 and 0.49 cmol/kg respectively.Soil with exchangeable calcium content<1.5 cmol/kg accounted for 31.1%,soil with exchangeable magnesium content<0.25 cmol/kg accounted for 31.7%,and soil with exchangeable potassium content ranging from 0.2 to 0.6 cmol/kg was more commonly found,accounted for 46.8%.The average soil base saturation was 49.5%,and soil with base saturation below 20%accounted for 15.3%.Base saturation,and the contents of exchangeable calcium and ex‐changeable magnesium were all extremely significantly and positively correlated with soil pH(H_(2)O),pH(CaCl_(2))and pH(KCl)(P<0.01).【Conclusion】The main sugarcane planting areas in Guangxi is suffering from severe soil acidifica‐tion,with most soils having a pH≤4.5.The lack of calcium and magnesium,low base saturation and high risk of alumi‐num toxicity have become the main characteristics of soil acidification in the main sugarcane planting areas in Guangxi.