快速检测土壤阳离子交换量的研究

针对土壤阳离子交换量检测行业标准推荐方法耗时长、操作繁琐,介绍了一种定氮仪配合漩涡振荡仪测定土壤阳离子交换量的快速蒸馏法,改进了离心处理环节和蒸馏步骤,讨论了关键流程和注意事项。该方法与行业标准乙酸铵法相比,试剂消耗明显减少,检测效率提高45%,检测精度和准确度符合标准要求,特别适于大批量及快速检出的土壤样品分析。     

设施蔬菜栽培对土壤阳离子交换性能的影响

以辽宁省沈阳市于洪地区设施菜地及其相邻旱田土壤为研究对象,测定土壤的有机质、阳离子交换量、交换性盐基离子组成和土壤盐基离子饱和度,分析设施蔬菜栽培对土壤阳离子交换量及交换性盐基离子组成的影响。结果表明:(1)与旱田土壤相比,设施土壤有机质含量明显增加,上下层土壤有机质平均含量分别为35.6 g kg-1和18.0 g kg-1,分别是旱田上下层土壤有机质含量的2.1倍和1.8倍;设施土壤阳离子交换量呈上升的趋势,土壤阳离子交换量与有机质含量呈极显著正相关关系(r=0.603**,n=50,r0.01=0.361)。(2)与旱田土壤相比,不同层次设施土壤交换性盐基总量均有所增加,交换性盐基离子中除交换性Ca2+含量变化不大之外,交换性K+、Mg2+、Na+含量均显著增加;不同层次设施土壤交换性K+、Mg2+、Na+饱和度显著高于旱田土壤,但交换性Ca2+饱和度和盐基饱和度呈下降趋势。     

Mulching effect of plant residues of chemically contrasting compositions on soil organic matter content and cation exchange capacity

Abstract

Effects of five types of plant residues [Acioa, presently Dactyladenia barteri, Gliricidia sepium, and Leucaena lecocephala prunings, maize (Zea mays) stover and rice (Oryza sativa) straw] applied as mulch on soil organic matter (SOM) content and effective cation exchange capacity (ECEC) were studied on an Alfisol in the humid tropics. Plant residue mulch resulted in a decline in SOM and ECEC during two years of cropping following six years of grass fallow. Rice straw mulch resulted in less and maize stover mulch in a greater decrease of SOM and ECEC than the other mulches. Decrease in SOM and ECEC is attributed to the mulching effect on the soil micro‐climate which enhanced the decomposition of SOM accumulated during the grass fallow prior to the initiation of the experiment. In order to maintain SOM for a tropical soil, plant residues with high lignin, polyphenols, and silica will have to be among residue species when applied in continuous cropping systems.     

Iron reduction and changes in cation exchange capacity in intermittently waterlogged soil

The long-term effects of intermittent flooding on soil properties were studied in field experiments on a Vertisol cropped with rice in Senegal. The dominant clay minerals were smectite and kaolinite. When the soil was reduced after flooding, its cation exchange capacity (CEC) increased to twice that of its oxidized, unflooded state. Mössbauer spectroscopy showed an increase in smectite structural Fe^II upon reduction, which explained a part of the increase in CEC. The rest of the increase was attributed to the removal of iron oxyhydroxide coatings by reductive dissolution. The reduction and dissolution of oxides under the field conditions were substantiated by analysis of the surfaces of vermiculites buried in the Ap horizons of the cropped and the non-cropped soils. The redox-induced CEC changes were found to be reversible after 22 cycles of rice cropping. Nevertheless, the structural Fe and free Fe contents of the rice field Ap horizon were less than those of soil in uncropped neighbouring land, suggesting that inundation induced weathering and eluviation of the minerals. The observed changes in CEC and related redox reactions may substantially modify proton, anion and cation balances in intermittently flooded soils.     

Statistical and geostatistical techniques for geospatial modeling of soil cation exchange capacity

Soil cation exchange capacity (CEC) is a main criterion of soil quality and pollutant sequestration capacity. This research was carried out to evaluate cokriging prediction map of soil CEC spatial variability with the principal components derived from soil physical and chemical properties. Two hundred and forty-seven soil samples were collected that 75% of them were used for training soil CEC and 25% for testing of prediction. The first principal component (PC1) was highly correlated with soil CEC (r = 0.81, P < 0.01), whiles there was no significant correlation between CEC and PC2 (r = -0.19). Then, the PC1 was used as an auxiliary variable for the prediction of soil CEC in cokriging method. The determination coefficient (R²) of cross-validation for the test dataset was 0.47 for kriging and 0.71 for cokriging. Therefore, according to the results, principal components that have the highest positive and significant correlation with the dependent variable have the most potential for cokriging prediction.     

镧的累积对红壤阳离子交换量及土壤溶液组成的影响

Pot and adsorption-exchange experiments were carried out by collecting the soil samples from the surface layer(0-15cm) of red soil at the Ecological Experiment Station of Red Soil,the Chinese Academy of Sciences,in Jiangxi Province of CHina.When concentration of the exogenous La^3 exceeded 400mg kg^-1,there was less non-exchangeable La^3 than exchangeable La^3 in the soil.Cation exchagne capacity of the soil changed slightly with increasing concentration of the exogenous La^3 in both experiments.However,in the adsorption-exchange experiment,when concentration of the exogenous La^3 was higher than 300mg kg^-1,exchangeable basic cations decreased significantly,while exchangeable hydrogen and exchangeable aluminum increased significantly compared with the control treatments.The amounts of base cations(Ca^2 ,Mg^2 ,k^ and Na^ )exchanged by La^3 in the supernatant solution increased with the concentration of the exogenous La^3 ,especially when concentration of the exogenous La^3 was higher than 50mg kg^-1.     

基于相似光谱匹配预测土壤有机质和阳离子交换量

土壤可见光-近红外波段光谱(350~2 500 nm)包含了大量的土壤属性信息,相同类型的土壤具有相似的光谱曲线特征,但相似光谱曲线是否具有相似的属性含量?探讨此问题可为土壤光谱库的应用提供依据,从而最终服务于快速获取土壤信息技术体系的构建。该研究以安徽宣城为研究区,根据母质、地形特征和土地利用等信息,采集91个典型土壤剖面,共含400个土壤发生层样品,测定了有机质(soil organic matter,SOM)和阳离子交换量(cation exchange capacity,CEC)含量,同时采用VARIAN公司的Cary 5000分光光度计测定了土壤光谱,并将光谱数据变换为反射率(R)、反射率一阶导数(FDR)和吸收度(Log(1/R))3种形式。该文采用光谱角(spectral angle mapper,SAM)、偏最小二乘回归(partial least square regression,PLSR)和SAM-PLSR(spectral angle mapper-partial least square regression,SAM-PLSR)3种方法预测土壤SOM和CEC。SAM方法是通过对测试集104个光谱曲线与参考集的296个光谱曲线进行相似性计算,并以此实现土壤SOM和CEC含量的预测。SAM-PLSR方法以SAM算法下的匹配结果作为建模样本建立PLSR模型和进行预测分析。结果表明,具有相似光谱曲线的土壤具有相似的SOM和CEC含量,SAM算法下相似光谱匹配可直接预测SOM(R2=0.78,RPD=2.17)和CEC(R2=0.82,RPD=2.41)。PLSR方法可很好地预测SOM(R2=0.87,RPD=2.77)和CEC(R2=0.87,RPD=2.59);相较之下,SAM-PLSR方法不仅可以更加准确预测SOM(R2=0.89,RPD=3.00)和CEC(R2=0.91,RPD=3.06),而且大大减少了建模样本的数量。该研究使可见光-近红外光谱可更加高效地用于土壤属性分析,并为土壤光谱数据库的建设及应用提供技术参考。     

Estimating cation exchange capacity using soil textural data and soil organic matter content: A case study for the south of Iran

Cation exchange capacity (CEC) is an important soil property that is used as an input data in soil and environmental models. Although CEC can be measured directly, its measurement is expensive and time-consuming, therefore pedotransfer functions can be used for estimating it from more readily available soil data. As CEC is highly dependent on soil texture, it may be successfully estimated from the soil textural data. In this study, 20 soils were selected from Fars province, in the south of Iran, and the values of CEC, soil organic matter content, and soil particle size distribution curve of each soil were measured and the geometric mean particle-size diameter (d _g ), and the summation of the number of spherical particles for whole parts of the soil particle-size distribution (N) were determined for each soil. Then, five multiple linear regressions were derived between CEC and mentioned soil properties. The results showed that more applicable equation for the study area was based on the percentages of clay, sand and soil organic matter content.     

Comparison of five methods to determine the cation exchange capacity of soil

Background

Cation exchange capacity (CEC) is a routinely measured soil fertility indicator. The standard NH₄OAc (pH 7) extraction procedure is time-consuming and overestimates actual CEC values of variable charge soils. Unbuffered extractants have been developed to measure the effective CEC (eCEC), but they differ in the type of index cation and extraction procedures.

Aim

This study was set up to systematically compare CEC values and exchangeable cation concentrations among different procedures and evaluate their practical aspects.

Methods

Five procedures were compared for (e)CEC, that is, silver thiourea (AgTU), cobalt(III) hexamine (Cohex), compulsive exchange (CE, i.e., BaCl₂/MgSO₄), BaCl₂ (sum of cations in single-extract), and NH₄OAc (pH 7). We applied these methods to a set of 25 samples of clay minerals, peat, or samples from soils with contrasting properties.

Results

The CEC values correlated well among methods (R² = 0.92–0.98). Median ratios of eCEC (AgTU as well as CE) to the corresponding eCEC (Cohex) value were 1.0, showing good agreement between eCEC methods, but NH₄OAc exceeded Cohex values (ratios up to 2.5 in acid soil). For BaCl₂-extracteable cations, the ratio ranged from low (<1.0) in acid soils (acid cations not measured) to high (>1.0) in high-pH soil (dissolution of carbonates). Multiple-extraction methods (CE and NH₄OAc) yielded more variation and increased labor.

Conclusions

The chemical properties of the sample cause method-specific interactions with chemical components of extractants. We found the Cohex method with ICP-MS detection to be the most efficient and cost-effective technique for determination of eCEC and exchangeable cations.     

红松人工林土壤阳离子交换量空间分布及其组成演变

以长白山红松人工林为研究对象,运用对比分析方法,对不同林龄红松人工林土壤阳离子交换量空间分布及其组成进行研究。结果表明：红松人工林土壤阳离子交换量和盐基饱和度均随着林龄增加而减小;土壤交换性,氢和交换性铝离子含量则相反,随林龄增大而增加;土壤阳离子交换量、交换性钙、镁离子含量表层大于底层,土壤阳离子交换量及其组成根际土壤大于非根际土壤;土壤阳离子交换量、交换性钙、交换性镁、交换性钠红松阔叶混交林大于红松人工林。     

Unlocking fixed soil phosphorus upon waterlogging can be promoted by increasing soil cation exchange capacity

Phosphorus (P) adsorbed by iron (Fe) oxyhydroxides in soil can be released when the Fe(III) minerals are reductively dissolved after soil flooding. However, this release is limited in tropical soils with large Fe contents and previous studies have suggested that P sorbs or precipitates with newly formed Fe(II) minerals. This hypothesis is tested here by scavenging Fe²⁺ in flooded soils by increasing the cation exchange capacity (CEC) of soil through resin application (30 cmol_c kg^?1; Na‐form). Three soils from rice paddies with contrasting properties were incubated in aerobic and anaerobic conditions with or without resin and with or without addition of organic matter (OM) to stimulate redox reactions. Dissolved Fe was 0.1–1.1 mm in unamended anaerobic soils and decreased to less than 0.07 mm with resin addition. Anaerobic soils without resin and aerobic soils with or without resin had marginal available P concentrations (<2 mg P kg^?1; anion‐exchange membrane P). In contrast, available P increased 3‐ to 14‐fold in anaerobic soils treated with resins, reaching 16 mg P kg^?1 in combination with extra OM. Application of Ca‐forms of resin did not stimulate P availability and dissolved Ca concentrations were larger than in unamended soils. Resin addition can increase P availability, probably by a combination of reducing solution Fe²⁺ (thereby limiting the formation of Fe(II) minerals) and increasing the OM solubility and availability through reducing dissolved Ca²⁺. The soil CEC is a factor controlling the net P release in submerged soils.     

Predicting carbon content in illitic clay fractions from surface area, cation exchange capacity and dithionite-extractable iron

We used the specific surface area (SSA), the cation exchange capacity (CEC) and the content of dithionite‐extractable iron (Fe_d) to predict the content of organic carbon in illitic clay fractions of topsoils from loess. We determined SSA (BET‐N₂ method) and CEC of clay fractions after removing organic C or reducing oxides or both. The CEC and the SSA of the carbon‐ and oxide‐free clay fraction explained 56% and 54% of the variation in C content, respectively. The Fe_d content of the clay fractions was strongly and negatively related to the C content, and with the SSA of the carbon‐free clay fraction it predicted C content almost completely (R² = 0.96). The results indicate that the amount of cations adhering to the silicate clay minerals and the size of the silicate mineral surface area are important properties of the mineral phase for the storage potential of C. The reason for the negative relation between iron oxides and C content remains unclear.     

Repeated applications of tannins and related phenolic compounds are retained by soil and affect cation exchange capacity

Retention of tannins, produced by plants, could be important for managing soil organic matter and nutrient cycling. However, we know little about the comparative retention of different classes of tannins and related compounds or if soils have a maximum storage capacity for them. To address these questions, forest, and pasture loam soils, collected at 0-5 cm (surface) and 10-20 cm (subsurface), were repeatedly treated with water (Control) or solutions containing condensed and hydrolyzable tannins or related phenolic subunits (10 mg g⁻¹ soil). Treatments included a polymeric flavonoid-based procyanidin from sorghum, catechin, tannic acid, β-1,2,3,4,6-penta-O-galloyl-d-glucose (PGG), gallic acid, and methyl gallate. After each application, soluble-C in supernatants was determined by oxidative-combustion infrared analysis and retention of treatment-carbon by soil was calculated as the difference between added and recovered soluble-C. An interaction between soil depth and treatment was evident through all applications with highest retention of both hydrophobic (PGG) and hydrophilic (procyanidin) tannins, compared to other phenolic compounds. For all treatments except gallic acid and methyl gallate, higher sorption occurred in surface soil, which contained more organic matter than subsurface soil. With each successive application, less additional treatment-C was retained by soil and the amount of C remaining in supernatants was correlated with the presence of phenolic substances. Cumulative retention by surface soil was more than 10.3, 8.5 and 6.4 mg C g⁻¹ soil for PGG, tannic acid, and procyanidin, several times higher than the other compounds. Soluble-C extracted from treated soil, with cool water (23 °C), was 1-2 orders of magnitude greater than Control samples and highly correlated with Prussian Blue (PB) phenolics, indicating some retained treatment-C was only weakly held on the soil. The final extraction, with hot water (80 °C), removed more soluble-C, particularly from surface samples, that contained fewer PB phenolics per unit soluble-C than cool water extracts. After all extractions more than 85% of sorbed procyanidin-C was retained by samples compared to 81% of methyl gallate, 79% of PGG, 74% of tannic acid, 50% of catechin, and 40% of the gallic acid. Total C, measured in soil after all extractions, was close to expected values, confirming tannins and phenolic compounds had remained in soil and were not otherwise lost. Cation exchange capacity was increased about 30% in subsurface and forest samples by PGG, a hydrolyzable tannin, but decreased by 30% and 35% in surface and pasture soil, respectively, by its monomer, gallic acid.     

Digital mapping of cation exchange capacity using genetic programming and soil depth functions in Baneh region,Iran

This study evaluates the performances of a combination of genetic programming and soil depth functions to map the three-dimensional distribution of cation exchange capacity (CEC) in a semiarid region located in Baneh region, Iran. Using the conditioned Latin hypercube sampling method, the locations of 188 soil profiles were selected, which were then sampled and analyzed. In general, results showed that equal-area quadratic splines had the highest R², 89%, in fitting the vertical CEC distribution compared to power and logarithmic functions with R² of 81% and 84%, respectively. Our findings indicated some auxiliary variables had more influence on the prediction of CEC. Normalized difference vegetation index (NDVI) had the highest correlation with CEC in the upper two layers. However, the most important auxiliary data for prediction of CEC in 30–60 cm and 60–100 cm were topographic wetness index and profile curvature, respectively. Validation of the predictive models at each depth interval resulted in R² values ranging from 66% (0–15 cm) to 19% (60–100 cm). Overall, results indicated the topsoil can be reasonably well predicted; however, the subsoil prediction needs to be improved. We can recommend the use of the developed methodology in mapping CEC in other parts in Iran.     

Predicting value of diagnostic soil properties on actual and potential cation exchange capacity (CEC) in andisols and andic soils

Abstract

Relationships between charge variation and diagnostic soil properties were studied in Andisols and andic subgroups of Inceptisols and Ultisols. Charge variation was calculated as the difference between “field” or actual cation exchange capacity (CECa), and potential CEC (1M NH₄OAc, pH 7). Methods used to estimate CECa (effective CEC, silver thiourea) were higly correlated. The relative charge variation was greater than 70% in Andisols with very low content of layer silicates. Active Al (Alo) was positively correlated with CEC‐NH₄ and negatively correlated with CECa. This result contributed to the explanation of the negative trend correlation observed between actual and potential CEC. The ratio CECa/Alo showed low values (<8) in Andisols. This parameter was also tested in 25 samples of Andisols described elsewhere. The predicting value of both Alo and CECa for a rough estimation of variable charge seemed apparent from the results obtained.     

Using support vector machines to predict cation exchange capacity of different soil horizons in Qingdao City,China

Agricultural, environmental and ecological modeling requires soil cation exchange capacity (CEC) that is difficult to measure. Pedotransfer functions (PTFs) are thus routinely applied to predict CEC from easily measured physicochemical properties (e.g., texture, soil organic matter, pH). This study developed the support vector machines (SVM)‐based PTFs to predict soil CEC based on 208 soil samples collected from A and B horizons in Qingdao City, Shandong Province, China. The database was randomly split into calibration and validation datasets in proportions of 3:1 using the bootstrap method. The optimal SVM parameters were searched by applying the genetic algorithm (GA). The performance of SVM models was compared to those of multiple stepwise regression (MSR) and artificial neural network (ANN) models. Results show that the accuracy of CEC predicted by SVM improves considerably over those predicted by MSR and ANN. The performance of SVM for B horizon (R² = 0.85) is slightly better than that for A horizon (R² = 0.81). The SVM is a powerful approach in the simulation of nonlinear relationship between CEC and physicochemical properties of widely distributed samples from different soil horizons. Sensitivity analysis was also conducted to explore the influence of each input parameter on the CEC predictions by SVM. The clay content is the most sensitive parameter, followed by soil organic matter and pH, while sand content has the weakest influence. This suggests that clay is the most important predictor for predicting CEC of both soil horizons.     

Changes in cation exchange capacity of some Andosols with dithionite-citrate treatment

Andosol is a soil widely distributed throughout Japan and is one of the important soils for the agriculture. The name “Ando soil” was given by THORP and SMITH (19) which means dark soil with an organic matter content ranging up to 30 per cent in the darkest members of the group. In 1964, the Soil Correlation Meeting on Volcanic Ash Soils (8), organized by FAO, adopted “Andosol” for volcanic ash soil of which the active fraction is predominated by amorphous material. Andosol, moreover, has many special properties such as high sorption capacity, high accumulation of organic matter, low bulk density and low stickiness. TAYLOR (18), accordingly, named them “amorphic soils”. The latest soil classification system, 7th Approximation (15) includes andosol under the suborder andepts.