EFFECTS OF ADSORBED CATIONS ON PHYSICAL PROPERTIES OF TROPICAL RED EARTHS AND TROPICAL BLACK EARTHS

Similar relative effects were obtained for plastic limits, percentage stable aggregates, and hydraulic conductivities when a tropical red earth, consisting predominantly of kaolin and iron oxide, and a tropical black earth consisting predominantly of montmorillonite, were saturated with Ca, Mg, K, or Na ions or combinations of these. Plastic limits were independent of the nature of the saturation cations, but were significantly dependent upon clay type. Percentage stable aggregates of artificially prepared aggregates and hydraulic conductivity were affected by the four cations in the order Ca = Mg > K Na and were also significantly affected by clay type. Combinations of the four cations generally gave intermediate effects with Ca-saturated soils more susceptible to deterioration by K or Na than Mg-saturated soils. The results confirm the generally deleterious effect of Na ions and show that K ions have effects similar to Na on the properties investigated. They suggest that heavy potash fertilization without liming may lead to structural deterioration of these soils.     

Relationship between water soluble and exchangeable soil cations for estimating plant uptake and leaching potential

Abstract

The relationship between water soluble and exchangeable cations (Ca, Mg, Na, and K) was investigated for surface horizons of 195 soils including many taxonomic categories and a wide range in physical and chemical properties from around the world. This will provide information on exchangeable soil cation solubility for use in estimating plant uptake and leaching potential. Amounts of water soluble and exchangeable cations were not consistently related (r² of 0.50, 0.08, 0.77, and 0.49 for Ca, Mg, Na, and K). High correlations were biased by high water soluble and exchangeable cation levels of a few soils that had 3.8‐ and 2.5‐fold greater mean than median values. The ratio of exchangeable to water soluble cations was closely related to cation saturation (r² of 0.87, 0.95, 0.95, and 0.93 for Ca, Mg, Na, and K, respectively). As the degree of saturation of the exchange complex by a certain cation increased, solubility Increased. A change in saturation had less effect on K than on Na, Mg, and Ca solubility. Only exchangeable soil cations (NH₄OAc extractable) are routinely measured and reported in soil survey reports, thus, water soluble levels may be determined from cation saturation. This will allow estimation of the amounts of cation that can potentially move in solution through the soil or be taken up by plants. Use of cation saturation, in addition to exchangeable content, will better characterize soil cation availability by representing quantity, intensity, and buffer factors.     

BASE CATION COMPOSITION OF PORE WATER,PEAT AND POOL WATER OF FIFTEEN ONTARIO PEATLANDS: IMPLICATIONS FOR PEATLAND ACIDIFICATION

Base cation (Ca, Mg, Na, K) concentrations in surface waters, pore waters and surface peats were determined along a mineral-poor to mineral-rich fen gradient for 15 south-central Ontario peatlands. Surface waters of the peatlands ranged in pH and alkalinity from 4.5 to 6.3 and 0 to 181 μeqL^-1, respectively. Both surface water and pore water Ca and Mg concentrations followed the expected decrease along the mineral-rich to poor-fen gradient. Surface water concentrations of Ca and Mg were significantly lower in the mineral-poor versus the moderately-poor and mineral-rich fens (P <0.05, ANOVA). Pore water concentrations of base cations were 3–5 fold less in mineral-poor vs. mineral-rich fens. In contrast to surface and pore waters, peat base cation concentrations did not decrease along the mineral-rich to mineral-poor fen gradient. Surface peat base cation concentrations were also independent of pore water cation concentrations, and local bedrock geology. Relative concentrations of base cations in surface peats of all peatlands were best described by the exchangeable cation capacity of the surrounding soils.     

Base cation-enhancing role of corn straw biochar in an acidic soil

Biochar affects base cation retention and leaching when it is used to enhance the base cation status of acidic soil. However, the details of its contribution are not yet clear. In this study, six loadings of corn straw biochar (0%, 2%, 4%, 6%, 8% and 10%, w/w) were applied to an acidic Ferralsol and incubated for 1 year. The results showed that the content of water-soluble and exchangeable base cations of K, Na, Ca and Mg increased with increasing levels of biochar in amended soil. The percentage of water-soluble Na, Ca and Mg of amended soil significantly decreased, while the percentage of exchangeable K, Ca and Mg increased significantly after the addition of biochar. For K and Na, biochar affected their leaching concentrations both as a source and by increasing the pH. For Ca, biochar reduced Ca leaching when the biochar loading was ≥4%, and the contribution increased from 30.8% to 100% at 4%–10% loading. For Mg, biochar reduced Mg leaching at biochar loadings 2%–10%, the reduction increasing from 22.0% to 70.5%. The results show that corn straw biochar can increase the content of the soil nutrient base cations K, Ca and Mg by increasing their exchangeable forms and enhance soil retention by decreasing their leaching. Thus, corn straw biochar can be used to effectively improve acidic soil base cation fertility.     

Relations entre concentration en cations dissous et debit de l'emissaire du glacier de Tsijiore Nouve (Valais)

Meltwaters were collected in the proglacial zone of the Tsijiore Nouve glacier near the snout. In the bilogarithmic coordinate system used, concentration of each major cation (Na, K, Ca, Mg) is a negative linear function of discharge. These relationships are explained by the effects of hydrologic conditions on cationic diffusion into the water from a sorbed state on the fine detritic fraction, and not by a mixture of ground water rich in dissolved cations with meltwaters of very weak concentration.     

降雨强度与坡度对径流中七种阳离子流失量的影响

针对密云水库周边地区坡地地貌,采用室内模拟降雨装置和ICP-MS质谱分析技术,研究了密云地区农田褐土在5种坡度和3种降雨强度交叉实验表层径流中K、Na、Ca、Mg、Al、Fe、Mn7种阳离子在不同降雨时段下的流失规律。结果表明在坡度和降雨时间段相同时,随着雨强的增加,大部分阳离子最大流失量逐渐增加,K、Mg、Fe、Mn规律性较强;在相同雨强和降雨时间段下,各阳离子流失量最大值所呈现的坡度不尽一致,但在雨强120mm/h时,K、Na、Ca、Mg、Fe流失量的最大值均呈现在25o坡度下;在坡度、雨强一致时,不同降雨时段内7种阳离子的流失量均呈现出随着时间的递增而逐渐增加的趋势。不同阳离子的流失总量之间随坡度的变化存在相关性,如在60mm/h和120mm/h降雨强度下,K、Ca流失量之间的相关系数分别达到0.974和0.953。各阳离子流失量在连续时间段下受径流量的影响不明显,但7种阳离子在1h的流失总量与径流量之间在相同降雨强度下随坡度变化均存在二次曲线关系,复相关系数平方>0.9。     

Retention and mobility of cations in a small peatland: trends and mechanisms

Inputs and net storage or release of cations can have a large impact on the acid-base balance of any ecosystem. Because of the absence of mineral soils, ion exchange and accretion in biomass are the major internal processes governing cation accumulation in peatlands. It is widely believed that peatlands have a large capacity to store cations, and thus to affect the acidity of surface waters. A long-term record of hydrologic and chemical inputs and outputs to the S-2 peatland in the Marcell Experimental Forest was used to construct annual and monthly mass balances for the four major cations. Bulk deposition and throughfall measurements suggest that deposition of Na, Ca and Mg has increased over the period 1971–1984; wet-only and dry bucket measurements do not show such a change. Seasonal and annual variations in cation inputs are not visible in the cation export from the peatland because the large cation reservoir on exchange sites in peat buffers the surface waters and prevents them from responding rapidly to changing inputs. Nevertheless, ion exchange represents a relatively minor source of acidity to this peatland, and accumulation of cations in woody biomass accounts for the majority of the cation retention. The major mechanism of retention in the peatland is different for each cation; accumulation in woody biomass is most important for Ca, storage on ion exchange sites in peat is most important for Mg, green plant tissues are the dominant site of K storage, and Na is bound by unknown mechanisms in the peat. Retention efficiencies show large annual variations but average 50% for Ca, 22% for Mg, 29–44% for Na, and 21% for K.     

Ameliorative effect of potassium on mice and tomato subjected to sodium salinization

Rice (Oryza sativa L. cv. Yamabiko) and tomato (Lycopersicon esculentum Mill cv. Saturn) plants subjected to Na-salinization (NA: 80 mmol( + ) kg^-1 Na) in hydroponics were grown after the addition of K at five concentrations (K1: 10, K2: 20, K3: 30, K4: 40, K5: 50 mmol( + ) kg^-1). The effect of K on their growth was analyzed in terms of transpiration, cation uptake, and transport. A similar tendency for the above parameters was obtained in both species. The addition of 10 mmol( + ) kg^-1 K improved the growth by decreasing the content of Na and increasing the K content of the plants. The growth of the plants, however, was reduced along with the increase of the K concentration and became comparable to that of NA at K5. The total cation content increased with the increase of the K concentration, which was due to the increase of the K content.

A close relationship was observed among the osmotic potential of the solution, cumulative transpiration, and dry weight for both species among the K treatments.

Addition of K suppressed the uptake of other cations by rice and tomato in the order of Na>Mg>Ca, with a very small suppression for Ca and Mg. The depression of Na uptake by K could be due to the antagonism between the two cations.

In rice, the addition of K resulted in a decrease of the uptake concentration (UC) of Na and an increase of that of K, but did not bring about any changes in the UC of Ca and Mg. It was worth noting that K1 and K2 led to a higher UC of Na than NA in tomato, while the trend of the UC of K, Ca, and Mg was similar to that in rice. The transport of Na and Ca to the tops of rice was not affected by the addition of K, while that of Mg increased by K addition. In tomato, the transport of all the cations was promoted by the increase of the K concentration.     

基于电导率和结构稳定性阳离子比的微咸水灌溉水质评估方法

电导率（Electrical Conductivity,EC）和结构稳定性阳离子比（Cation Ratio of Soil Structural Stability,CROSS）是评估微咸水对土壤渗透性能影响的重要指标。虽然CROSS全面地考虑了Na+、K+、Ca2+和Mg2+对土壤结构稳定性的复杂影响,但CROSS的离子浓度系数在不同地区的适用性存在差异,有必要根据当地的水质条件确定基于EC和CROSS评估方法的分类标准。该研究旨在分析CROSS替代钠吸附比（Sodium Adsorption Ratio,SAR）评估水质危害的合理性以及其在河套灌区的适用性。在河套灌区不同区域采集73份地下水水样,并采用EC和SAR、EC和CROSS对其进行评估。结果表明,基于2种方法的地下水分类结果中,仅有34.25%的水样分类结果相同,并且不同的CROSS计算方法（基于阳离子相对絮凝能力（Flocculation）的CROSSf、相对分散能力（Dispersion）的CROSSd和优化的（Optimal）CROSSopt）在河套灌区的适用性也不相同。建议采用CROSSd或CROSSopt,并结合土壤盐分和离子浓度评估河套灌区地下水水质。该评估方法更全面地考虑了地下水和土壤中的离子组成对土壤渗透性能的影响,有效避免了不合理的微咸水利用导致的土壤结构恶化等问题,可为微咸水的安全可持续利用提供理论支撑。     

Modelling of sorption experiments and seepage data of an Amazonian Ultisol subsoil under cropping fallow

The results of physico-chemical investigations of an Ultisol subsoil under a 2-year old fallow in eastern Amazonia are presented. Subsoil chemistry was studied using 4 different approaches: i) concentrations of H, Na, K, Ca, Mg, Mn, Al, and Fe in seepage water were measured under field conditions, ii) the equilibrium soil chemistry was studied in sequential batch experiments where the soil was treated with different solutions, iii) results of batch experiments were simulated with a chemical equilibrium model, and iv) the seepage data were calculated using selectivity coefficients obtained by modelling the batch experiments. The model included multiple cation exchange, precipitation/dissolution of Al(OH)₃ and inorganic complexation. Cation selectivity coefficients were pK_x/Ca^sel: X = Na: 0.3, K: 0.8, Mg: ?0.1, and Al: 0.4. The amount of cations sorbed ranged from ?0.2 to 2.0 (K), ?0.7 to 2.3 (Mg), ?1.6 to 1.8 (Ca), ?4.8 to 3.6 (Al) and 0.0 to 8.5 (Na) mmol_c kg^?1. The model predictions were good with values lying within 0.3 pH units (for the pH range 3.7 to 7.2), and 3% of CEC for individual cations. The most important proton buffer reaction seemed to be the dissolution of gibbsite and a large release of Al into the soil solution. When selectivity coefficients obtained by the modelling procedure were used to predict the field data for cation concentrations in the seepage water, they decreased in the following order: Na > K > Ca > Mg > Al. These calculated values were similar to the measured order: Na > Ca > K ≈ Mg > Al. Thus the options for managing these soils should be carefully chosen to avoid soil acidification which may result from inappropriate use of fertilizer during the cropping period.     

Ionic equilibria,selectivity and diffusion of cations in soil as influenced by anion additions

Abstract

An experiment was carried under controlled conditions to investigate the influence of the anions, H₂PO₄ ^‐. and Cl on the ionic equilibria, selectivity and effective diffusion of Rb, K, Na, Ca, Mg in two Indiana soils.

Additon of anions to the soils increased the concentration of cations in soil solution. In both the soils receiving H₂PO₄ ^‐, lower cation concentrations were found in the soil solution than in those receiving Cl^‐ . Additon of H₂PO₄ ^‐and Cl^‐ reduced the ion selectivity coefficient, k, for various homovalent (Rb/K, Rb/Na, K/Na, Ca/Mg) and mono‐divalent ion pairs (Rb/Ca, Rb/Mg, K/Ca, K/Mg). In Zanesville soil treatments receiving H₂PO₄ ^‐ had lower k values for mono‐divalent cations than treatments receiving Cl^‐. However, no such conclusions could be drawn for Raub soil. Soils treated with H₂PO₄ ^‐ had higher k values for homovalent cations than Cl^‐ treated soils. The differences in the selectivity of adsorption in these two soils might be attributable to the differences in the type and nature of exchange materials and cation concentrations on the exchange phase.

Addition of H₂PO₄ ^‐ or Cl^‐ enhanced the magnitude of effective diffusion coefficient. (De) of all the cations under considerations. The magnitude of effective diffusion coefficient for cations was lower for H₂PO₄ ^‐ treated soils than Cl^‐ treated soils. Such a reduction in De is related to the reduction in cation concentration in soil solution thereby increasing the buffer capacity for the ions under consideration.     

EFFECT OF SOIL pH AND ORGANIC MATTER ON LABILE ALUMINIUM IN SOILS UNDER PERMANENT GRASS

The rates of extraction of Na, K, Mg, Ca, and Al with 1M NH₄ NO₃ from the mineral-and organic-rich layers of some Park Grass (Rothamsted) soils were measured at the pH of the soil. Below pH 3.7 exchangeable Al, derived from the kinetics curve, increases with decreasing soil pH and is less in the organic-rich layer. The sum of the basic exchangeable cations, ∑(Na + K + Mg + Ca), increases with increasing soil pH and is more in the organic-rich layer. The extraction of exchangeable Al obeys first order kinetics, the rate constant being similar for all the soils (mean value 36 ± 7 × 10^?6|s^?1), which implies that exchangeable Al is released from surfaces with similar properties for the adsorption of Al, and that the rate is not affected by soil pH and organic matter. The rate of extraction of non-exchangeable Al is the same in the mineral-and organic-rich layers of each soil, and is maximal at about pH 3.7, decreasing sharply at more and less acid pH values.     

Long-Term Effects of Wheat Production Management Practices on Exchangeable Base Cations and Cation Exchange Capacity of a Plinthosol in Semi-arid South Africa

Changes in soil fertility indicators are mainly the result of management practices and usually influence crop yields over the long term. This study shows the effects of long-term wheat production management practices on exchangeable base cations and cation exchange capacity (CEC). Applied field treatments included two methods of straw management (unburned, burned), three methods of tillage (no tillage, stubble mulch, plowing), and two methods of weeding (chemical, mechanical). Samples were collected at six soil depths and analyzed for potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), and CEC. Burned wheat straw resulted in greater K and lower Ca concentrations compared to unburned wheat straw. No-tillage treatment increased K, Ca, Mg, Na, and CEC compared to both stubble mulch and plowing. Chemical weeding improved Na and CEC compared to mechanical weeding. The treatment combinations had positive influences mainly on CEC. Unburned straw and moldboard plowing with respect to burned straw and no tillage enhanced grain yield with 8%.     

Laboratory Dissolution Studies of Rocks from the Borrowdale Volcanic Group (English Lake District)

Laboratory studies were conducted to investigate the rates ofrelease of Na, Mg, Al, Si, K, Ca and Fe from 10 samples of metamorphosed igneous rock of the Borrowdale Volcanic Group (BVG), consisting mainly of plagioclase feldspars, chlorite andquartz, with minor amounts of hornblende, epidote and carbonates.Experiments were performed using freshly-prepared rock pieces (ca. 12 mm cubes), in batch mode, but with frequent changes of the solution phase so that accumulation of dissolved solutes wasminimised. The initial element release rates were relatively high, but declined with time to reach approximate (pseudo-) steady state conditions. Element release rates declined withpH in the pH range 2–7, the dependence upon pH decreasing in the order Al ～ Fe > Si > Mg ～ Ca > K ～ Na. Thepseudo-steady state rates for Si were comparable to steady state values for single minerals. Calcium showed the greatestsample-to-sample variation (more than 100-fold). Rock dissolutionwas far from stoichiometric, with Ca and Mg being present in thesolution phase in proportions greater than in the rock, and Al and Si in lower proportions. In some samples the release rates ofMg and Ca were equal, while in others the Ca rate was up to 100times that of Mg. The rate of release of Ca is correlated with the carbonate content of the rocks. The results indicate that the main source of Ca in the faster-dissolving samples is calcite, while the highest release rates of Mg are consistent with dissolution of dolomite. Aluminium, Si and Fe are probablyreleased predominantly from chlorite. The results are discussed in terms of the supply of base cations to stream waters drainingcatchments underlain by rocks of the BVG.     

Potassium additions on ionic equilibria,selectivity and diffusion of cations in soils

Abstract

In a soil system variation in the concentration of any one ion as induced by external addition might bring changes in the ionic‐equilibria, diffusion rate and strength of adsorption of all the ions involved. In four Indiana soils the changes in ionic equilibria, selectivity coefficient and rate of diffusion coefficient for K, Na, Ca and Mg were investigated at 5 levels of added K. The experiments were carried out under controlled laboratory conditions by incubating soils for 3 weeks at 25C. All soils had a greater fraction of Ca and Mg on the exchange phase than in solution, whereas with K and Na the reverse occurred. Potassium adsorption isotherms for all the soils differed indicating the difference in the nature of soil materials involved. Chalmers soil with high clay content with high exchange capacity had high differential buffer value for K. In all the soils, K was adsorbed preferentially to Na at all the levels of K addition, Calcium was adsorbed preferentially to Mg on the Zanesville and Toronto soils. However, in Chalmers and Raub soils, reverse was observed when the level of K addition was exceeded 1.0 and 0.5 me K/100g soil, respectively. This difference in Mg for Ca is attributed to smaller proportion of Mg saturation on the exchange surface. Divalent cations were preferentially adsorbed over monvalent ions. Increasing levels of K addition increased the diffusion rates of all the ions under consideration. The rate of diffusion for K and Ca were governed by concentrations of these ions on the exchange and solution phase.     

Forest soil chemical changes between 1949/50 and 1987

Soil profiles from the Alltcailleach Forest in north-east Scotland originally sampled in 1949/50 were resampled in 1987. Soil pH, exchangeable Ca, Mg, K and Na, extractable Al and cation exchange capacity were measured on the original stored and resampled soils. Chemical changes were characterized by decreases in pH, base cations, base saturation and cation exchange capacity. Extractable amounts of Al increased. Sequential leaching experiments showed a significant increase in the amount of extractable sulphate in mineral soil horizons. Changes in soil chemistry were interpreted to result from a combination of nutrient depletion caused by tree growth, natural pedogenic processes and atmospheric pollution effects.     

Elemental and/or cation ratio efficiency of corn hybrids grown on an infertile soil inadequate in magnesium

Abstract

Magnesium deficiency in corn (Zea mays L.) is often attributed to the low levels of Mg in soils. This study was conducted to determine elemental and/or cation balance efficiency of corn hybrids grown on a soil low in available Mg, Among the 15 hybrids tested, no differential efficiency in ear leaf concentration of P was found at two planting dates. Leaf concentrations of Zn and Fe were influenced by planting date for all hybrids but interactions between hybrids and planting date were found only for K, Ca, Mg concentrations and the sum of the Meq Ca + Mg/100 g, the Meq K + Ca + Mg/100 g, and the K/Ca and K/Ca + Mg ratios. Planting dates did not Influence the K/Mg ratio among hybrids. Large differences in efficiency of K, Ca, and Mg were found but these cations were found to have large Interactions. Data show that Ca and Mg efficient hybrids are less efficient in K than Ca and Mg inefficient hybrids. It should be possible to breed corn hybrids for better cation balance efficiency for use on infertile soils low in avallable Mg.     

Oxidation-induced leaching of sulphate and cations from acid sulphate soils

Leaching of sulphate and cations from horizon samples of two acid sulphate soils (0.9 to 1.6% S in subsoil) was studied in the laboratory. Samples were incubated and eluted with water at 20 °C and 5 °C until apparent exhaustion of leachable S resources. The leachates were analyzed for pH, SO₄-S, Fe, Al, Mn, K, Ca, Mg, and Na. Oxidation of sulphide was retarded at the lower temperature. From all the originally water-logged samples the sulphate formed was initially washed out with base cations (mainly with Mg), but the proportion of acid counter ions (predominantly Al) increased with proceeding oxidation and acid formation. In the most acid leachates, pH was 2.6 to 2.8. In the transition layer between reduced and oxidized horizons, sulphide oxidation had been going on for some time, and acid cations were the main counter ions for sulphate already at the beginning of the experiment. In the totally oxidized surface horizons, sulphate was leached only in moderate quantities, and the sum of cation equivalents (mainly base species) exceeded that of sulphate, suggesting some removal of other anions. Leaching losses in the laboratory experiment, corresponding to drainage-induced loading of waters in field experiments during the course of many decades, point out the environmental danger associated with deep drainage of potentially acid sulphate soils.     

Relationship between cationic balance in the chicory root and internal browning of the chicon

During the vegetative period of the biennial chicory plant (Cichorium intybus L., witloof type) nutrient solutions with a constant cationic content but variable proportions of potassium (K), calcium (Ca), and magnesium (Mg) were applied to the plants grown on perlite. This resulted in taproots varying in cation content: K and Mg decreased and Ca increased in the high‐Ca series compared with the control. A forcing experiment of the taproots in darkness with a standard nutrient solution resulted in a low percentage of brown axes (11%), a Ca‐deficiency symptoms in the chicons from high Ca‐treated roots as compared with 45% in the control. Analysis of the cations in chicons and roots after forcing showed a prevalence of K and Mg migration in comparison with sodium (Na) and Ca towards the chicon. During the first days of forcing, mineral nutrition of the chicon relied only on root reserves and competition between Ca and K‐Mg was reduced in the high Ca‐treated roots, therefore limiting brown axis initiation. Later on, the contribution of the external medium was greater in the high‐Ca series, notably for K, thus involving a higher water and Ca‐linked flux towards the chicon which kept it above the critical level of internal browning expression.