Effect of Soil Properties on Boron Adsorption and Release in Arid and Semi-Arid Benchmark Soils

The adsorption isotherms indicated that the adsorption of boron (B) increased with its increasing concentration in the equilibrium solution. The Langmuir adsorption isotherm was curvilinear and it was significant when the curves were resolved into two linear parts. The maximum value of adsorption maxima (b1) was observed to be 7.968 mg B kg^?1 in Garhi baghi soil and the bonding energy (k) constant was maximum at 0.509 L mg^?1 in Jodhpur ramana soil. The Langmuir isotherm best explains the adsorption phenomenon at low concentrations of the adsorbent, which of course was different for different soils. There was significant correlation between b1 and clay (r = 0.905**), organic matter contents (r = 0.734*), and cation exchange capacity (CEC; r = 0.995**) of soils. A linear relationship was observed in all the soils at all concentration ranges between 0 and 100 mg B L^?1, indicating that boron adsorption data conform to the Freundlich equation. Soils that have a higher affinity for boron adsorption, like Garhi baghi, tended to desorb less amount of boron, that is, 43.54%, whereas Ballowal saunkhari desorbed 48.00%, Jodhpur ramana 48.42%, and Naura soil 58.88% of the adsorbed boron. Boron desorption by these soils is positively and significantly correlated with the sand content (r = 0.714**) and negatively with clay content (r = ?0.502*) and CEC (r = ?0.623**). The maximum value of 37.59 mg kg^?1 for desorption maxima (Dm) was observed in Garhi baghi soil and also a constant related to B mobility (Kd) was found to be maximum in Garhi baghi (0.222 L kg^?1) soil Note: *P<0.05; ^**P<0.01.     

Organic Matter and Mineralizable Nitrogen Relationships in Wetland Rice Soils

Abstract

Soil nitrogen (N) supply plays a dominant role in the N nutrition of wetland rice. Organic matter has been proposed as an index of soil N availability to wetland rice. This is based on the finding that mineralizable N produced under waterlogged conditions is related to soil organic carbon (C) and total N. The relationship between organic matter and mineralizable N is a prerequisite for determining the N requirement of wetland rice. However, no critical analysis of recent literature on organic matter–mineralizable N relationships has been made. This article evaluates current literature on the relationships of mineralizable N or ammonium N production with soil organic C in wetland rice soils. A number of studies with diverse wetland rice soils demonstrate a close relationship of N mineralized (ammonium‐N) under anaerobic conditions with organic C or total N. However, a few recent studies made on sites under long‐term intensive wetland rice cropping showed that strong positive relationships of mineralizable N with organic C or total N do not hold. Clearly, both quantity and quality of organic matter affect N mineralization in wetland rice soils. Future research is needed to clarify the role of quality of organic matter, especially its chemistry, as modified by the chemical environment of submerged soils, on the mineralization of organic N in wetland rice soils.     

黄棕壤中活性有机碳对Cu吸附的影响

通过盐酸酸化法来去除4种不同利用方式黄棕壤的活性有机碳（AOC）,得到相对稳定的有机碳土壤,用于研究去除活性有机碳前后对Cu2＋吸附行为的影响。结果表明,黄棕壤去除有机碳前后,对Cu2＋吸附量与平衡液浓度的关系符合Langmuir方程和Freundlich方程,其拟合都呈现极显著相关（P〈0.01）,去除AOC后,黄棕壤各层次对Cu2＋的最大吸附量明显降低,是原土Cu2＋最大吸附量的10%～30%。盐酸酸化法对4种不同利用方式的黄棕壤有机碳的去除率为30%～75%,对Cu2＋吸附的减少率为54%～86%。去除活性有机碳前后,有机碳含量与对Cu2＋的吸附量都呈显著线性相关。土壤有机碳的去除率与对Cu2＋吸附的减少率间相关性达到极显著水平。     

Comparison of Five Adsorption Isotherms for Prediction of Zinc Retention in Calcareous Soils and the Relationship of their Coefficients with Soil Characteristics

Abstract

Zinc (Zn) deficiency is believed to be a consequence of reactions taking place between soluble Zn and the soil solid phase. This study was carried out to obtain quantitative relationships between Zn in equilibrium solution and that retained by the soil solids in calcareous soils. Twenty calcareous soils (saturated paste pH 6.9–7.9; calcium carbonate equivalent 4.64–22.80%) from Tehran province, Iran, were equilibrated with varying solution concentrations of Zn, and the amounts removed from the solution were used to check the fit to five adsorption isotherms, namely, Freundlich, Langmuir, Temkin, Gunary, and two‐surface Langmuir. Adsorption data of all soils showed statistically significant fit to the first four adsorption isotherms, but only 7 of the 20 soils tested showed fit to the two‐surface Langmuir. Coefficients of the adsorption isotherms showed statistically significant relationship with soil characteristics. Clay percentage, calcium carbonate equivalent percentage, and cation exchange capacity appeared to be the most influential soil characteristics with regard to Zn adsorption, whereas soil organic matter seemed to be of no importance under the conditions of this study.     

Adsorption and Desorption of Copper in Pasture Soils

Abstract

Copper (Cu) is bound strongly to organic matter, oxides of iron (Fe) and manganese (Mn), and clay minerals in soils. To investigate the relative contribution of different soil components in the sorption of Cu, sorption was measured after the removal of various other soil components; organic matter and aluminum (Al) and Fe oxides are important in Cu adsorption. Both adsorption and desorption of Cu at various pH values were also measured by using diverse pasture soils. The differences in the sorption of Cu between the soils are attributed to the differences in the chemical characteristics of the soils. Copper sorption, as measured by the Freundlich equation sorption constants [potassium (K) and nitrogen (N)], was strongly correlated with soil properties, such as silt content, organic carbon, and soil pH. The relative importance of organic matter and oxides on Cu adsorption decreased and increased, respectively, with increasing solution Cu concentrations. In all soils, Cu sorption increased with increasing pH, but the solution Cu concentration decreased with increasing soil pH. The cumulative amounts of native and added soil Cu desorbed from two contrasting soils (Manawatu and Ngamoka) during desorption periods showed that the differences in the desorbability of Cu were a result of differences in the physico‐chemical properties of the soil matrix. This finding suggests that soil organic matter complexes of Cu added through fertilizer, resulted in decreased desorption. The proportions of added Cu desorbed during 10 desorption periods were low, ranging from 2.5% in the 24‐h to 6% in the 2‐h desorption periods. The desorption of Cu decreased with increasing soil pH. The irreversible retention of Cu might be the result of complex formation with Cu at high pH.     

Comparison of Adsorption Isotherm Equations to Describe Boron Behavior in Soils Affected by Organic and Mineral Fertilization

The effects of different fertilization techniques—mineral [21% nitrogen (N)], organomineral (10% N), mycorrhiza inoculumns, wine-producing residues (three different formulas: distiller's residue, 2.2% N; anaerobic digestate, 2.8% N; and the same plus mycorrhizas inoculum), and compost by farm residues (2.0% N)—on adsorption of boron (B) were investigated. The soils, collected after a triennial lettuce (Lactuca sativa L. cv. ‘Bacio’) cultivation, were equilibrated using six B concentrations [0, 1, 5, 20, 50, and 100 mg B L^?1, as boric acid (H₃BO₃)]. The B adsorption was studied at two soil mass (m_s) to solution volume (v_s) ratios, m_s/v_s = 0.5 and 1, and the Langmuir, Eadie–Hofstee, Freundlich, and Temkin adsorption equations were fitted to the B adsorption data. The proportion of adsorbed B was gradually less in the more concentrated solutions, with differences in m_s/v_s ratio and in treatments: the percentage of B adsorbed was greater for m_s/v_s = 0.5 and for distiller's residue and mineral fertilizer. The Freundlich isotherm represented the measured B adsorption data well; at m_s/v_s = 0.5, the values of Freundlich adsorption maxima Xm varied from 93.14 to 111.88 mg kg^?1 (organomineral fertilizer and distiller's residue, respectively; at m_s/v_s = 0.5) and from 32.14 to 40.32 mg kg^?1 (mineral fertilizer and control, respectively; at m_s/v_s = 1). In our study, generally the B adsorption was greater with mineral fertilizers and distiller's residue, whereas the organomineral fertilizer led to a decrease in B adsorption. The parameters of adsorption isotherms were significantly correlated, at various degrees, with the exchangeable cation sodium. The adsorption isotherms were well explained by the lower soil mass to volume solution ratio in the order Freundlich > Temkin ≌ Langmuir > Headie–Hofstee.     

Boron adsorption and desorption in some acid soils of West Bengal,India

Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe₂O₃ and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe₂O₃, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.     

Adsorption/Desorption of Organic Anions in Brazilian Oxisols

Abstract

Organic anions affect solute mobility in soils. This study evaluated citrate and oxalate adsorption (0 to 4 mmol L^?1, soil–solution 1∶100, pH 5.5, ionic strength 30 mmol L^?1 as NaCl, 72‐h reaction) and desorption (pH 5.5, 30‐mmol L^?1 NaCl, 72 h) on A‐ and B‐horizon samples of two Brazilian Oxisols. Langmuir and Freundlich isotherms were used to assess adsorption maximum, distribution coefficients (Kf, Ku), and buffer index. Adsorption maximums (mol kg^?1) for red Latossol‐A, red Latosol‐B, red‐yellow Latosol‐A, and red‐yellow Latosol‐B horizons follow: citrate 0.0318, 0.0272, 0.0289, 0.0392; oxalate 0.0641, 0.0329, 0.0538, 0.0380. Kf (mol^1?1/n kg^?1 L^1/n) follows: citrate 0.3550, 0.3781, 0.4211, 0.2024; oxalate 1.0916, 0.0637, 1.8228, 0.0922. Buffer index (mol kg^?1)(mol kg^?1)^?1 follows: citrate 0.0841, 0.0756, 0.0738, 0.0264; oxalate 0.3787, 0.0862, 0.3233, 0.1082. Both anions showed great affinity for variable‐charge soils. The distribution curves for Ku showed higher adsorption energy in B‐ than in A‐horizons.     

Cultivation-Induced Effects on the Organic Matter in Degraded Southern African Soils

We studied quantitative and qualitative changes in soil organic matter (SOM) due to different land uses (reference woodland versus cultivated) on six soils from Tanzania (Mkindo and Mafiga), Zimbabwe (Domboshawa and Chickwaka), and South Africa (Hertzog and Guquka). Structural characteristics of the humic acids (HAs) were measured by Curie-point pyrolysis–gas chromatography/mass spectrometry (P_y–GC/MS) and solid-state ¹³C nuclear magnetic resonance (CPMAS ¹³C NMR) spectroscopy. Significant changes in concentration and composition of SOM were observed between land uses. Losses of organic carbon after cultivation ranged from 35% to 50%. Virgin soils showed large proportions of colloidal humus fractions: humic acids (HAs) and fulvic acids (FAs) but negligible amounts of not-yet decomposed organic residues. The change in land use produced a contrasting effect on the composition of the HAs: a noteworthy “alkyl enhancement” in Mkindo soil and “alkyl depletion” in Chikwaka and to a lesser extent in Domwoshawa. The remaining soils displayed only minor alterations.     

Distribution and Availability of Zinc and Copper in Benchmark Soils of Pernambuco State,Brazil

Abstract

The benchmark soils collection of Pernambuco state contain 13 of the 14 soil orders of the Brazilian System of Soil Classification. Thus, information on zinc (Zn) and copper (Cu) status in such soils is useful as a reference of micronutrient distribution and availability in a representative set of Brazilian soils. The present work was performed to assess Zn and Cu distribution into operationally defined fractions of benchmark soils of Pernambuco state. In addition, chemical extractants, with contrasting chemical properties, were used to assess the availability of these micronutrients to relate such values with fertility guidelines concentrations and with the fractions defined by the sequential extraction. The results demonstrated that the organic matter was the most important fraction retaining Zn and Cu in the studied soils, as indicated by the sequential extraction. The Zn availability in the majority of the soils (90% of the samples) is sufficient to meet the requirement of the major field crops, although the available Cu concentrations are below the critical levels for plant growth in 46% of the analyzed samples. Mehlich‐1 extractant appeared to be the most efficient in predicting the availability of Zn in the soils because of its better correlation with exchangeable and organic fractions. DTPA and Mehlich‐3 were the most efficient extractants for the evaluation of Cu availability, as suggested by the better correlation with organic matter, which is the main pool of available Cu in the soils.     

Approaching a Standardized Method for the Hot-Water Extraction of Peat Material to Determine Labile SOM in Organic Soils

Peatland soils are the most effective and important long-term terrestrial carbon (C) storages. To estimate potential C loss, a valid characterization of soil decomposability, in particular the labile fraction, is of great interest. One of the most labile fractions is hot-water-extractable organic matter (HWOM), often measured as hot-water-extractable carbon (C_hwe) and nitrogen (N_hwe). Various studies describe different extraction procedures for mineral soils. Because of methodical differences, it is difficult to compare extracted HWOM amounts directly to each other. For peatland soils, few studies exist. The aim of the present study is the development of a standardized method for the hot-water extraction of peat materials. Therefore, we extracted HWOM in various replicates from different peats on the basis of a standardized extraction method for mineral soils (1 h extraction at 100 °C). We tested how differences in soil/water ratios, extract treatment (filtering vs. not filtering), and sample pretreatment (freeze drying vs. air drying) influence HWOM amounts. The results clearly illustrated the influence of changing soil/water ratios on HWOM amounts. Mean C_hwe concentrations ranged between 8 and 34 g kg^?1 whereas N_hwe ranged between 0.2 and 2.6 g kg^?1. We recommend the extraction under soil/water ratios of 1/800 to provide sufficient volume of solvent for C_hwe. If relative differences for N_hwe amounts are greater than 15 percent, samples should be extracted again under soil/water ratios greater than 1/300 to avoid analytical errors due to unintended dilution effects. Filtering of centrifuged and decanted extracts before analysis is not necessary. Peat material should be either air dried or freeze dried before extraction.     

Charge Distribution and the Interactive Effect of pH and Ionic Strength on Phosphate Adsorption Properties of Two Benchmark Soils from Botswana

The constraint imposed by phosphate (PO₄) deficiency on soil fertility in Botswana necessitated the study of ionic strength (μ) and pH effects on electric charge distribution and PO₄ adsorption of two representative soils: Typic Pellustert and Typic Haplustalf. Electric charge increased with increasing soil pH, but the effect of µ on electric charge distribution was indistinct. The point-of-zero-salt-effect (PZSE) occurred at pH 4.8 in the Pellustert and at almost 6.0 in the Haplustalf. Ionic strength decreased PO₄ adsorption in the Pellustert, but increased it in the Haplustalf. The Scatchard and reciprocal linearization of the Langmuir model adequately described PO₄ adsorption of the soils under varying µ and pH × µ conditions. The PO₄ adsorption maxima (M) and affinity index (b) decreased with increasing µ in the Pellustert, but not in the Haplustalf. The decreasing M and b with increasing µ in the Pellustert was explained by electrostatic repulsion from the highly negative charge surface, whereas the increasing M and b with increasing µ in the Haplustalf was attributed to enhanced access to the surface sorption sites due to compression of diffuse double layer. Under varying pH × µ conditions, PO₄ sorption sites were resolved into low- and high-energy sites, depending on the concentration of added PO₄. Because b is related to the ease of PO₄ detachment from soil surfaces into solution for plant uptake or leaching, PO₄ added to this Pellustert at µ > 0.01 would likely leach freely, and hence µ monitoring is imperative for PO₄ fertilization strategy of this Pellustert.     

模拟酸雨对荔枝果园土壤磷素等温吸附与解吸特性的影响

采用等温吸附试验方法研究了模拟酸雨对荔枝果园土壤磷的吸附与解吸特性的影响。试验结果表明,不同处理间土壤对磷的最大吸附量(Xm)为pH2.5>pH4.5>CK=pH6.5,其中pH2.5的酸雨淋溶处理对磷的最大吸附量(Xm)与其它处理间差异显著;土壤吸附磷的解吸量(Xd)分别与相应的吸附量(X)和原平衡溶液浓度(C)呈显著的指数相关和线性相关,随着土壤对吸附量的增加,土壤磷的解吸量呈指数增长。     

Characterization of the Soil Organic Matter in Agricultural Mine Spoils and Reclaimed Soils Treated with Organic Amendments

Recycling organic waste in agricultural soils is a valid solution. We performed short‐term experiments to investigate the fate of urban sludge and composts, in mine spoils, cultivated or uncultivated, and reclaimed soils located in Florence and Milan, Italy. The samples, either treated or untreated, were fractionated by density into light (<1.63 Mg m^?3) and heavy (>1.63 Mg m^?3) fractions. The fractions were analyzed for total carbon (C) and nitrogen (N) contents and for δ ¹³C and δ ¹⁵N isotopes, and they were characterized by ¹³C NMR spectroscopy. Treatment increased the heavy fraction. The addition of sludge in the Florence area acts in synergy with the cultivation, increasing the light fraction (LF). In the Milan area, the LF tends to be decomposed and apparently transformed into HF. The addition of amendments or cultivation enhances the decomposition with release of carbon dioxide. For future research, we suggest lengthening the time of the experiments to integrate climatic variations.     

Distribution of Zinc Fractions in Some Major Soils of India and the Impact on Nutrition of Rice

Abstract

Speciation study of microelements in soils is useful to assess their retention and release by the soil to the plant. Laboratory and greenhouse investigations were conducted for five soils of different agro‐ecological zones (viz., Bhuna, Delhi, Cooch‐Behar, Gurgaon, and Pabra) with diverse physicochemical properties to study the distribution of zinc (Zn) among the soil fractions with respect to the availability of Zn species for uptake by rice plant. A sequential extraction procedure was used that fractionated total soil Zn into water‐soluble (WS), exchangeable (EX), specifically adsorbed (SA), acid‐soluble (AS), manganese (Mn)‐oxide‐occluded (Mn‐OX), organic‐matter‐occluded (OM), amorphous iron (Fe)‐oxide‐bound (AFe‐OX), crystalline Fe‐oxide‐bound (CFe‐OX), and residual (RES) forms. There was a wide variation in the magnitude of these fractions among the soils. The studies revealed that more than 90% of the total Zn content occurred in the relatively inactive clay lattice and other mineral‐bound form (RES) and that only a small fraction occurred in the forms of WS, EX, OM, AFe‐OX, and CFe‐OX. Rice (Oryza sativa L.) cultivars differ widely in their sensitivity to Zn deficiency. Results suggested that Zn in water‐soluble, organic complexes, exchange positions, and amorphous sesquioxides were the fractions (pools) that played a key role in the uptake of Zn by the rice varieties (viz., Pusa‐933‐87‐1‐11‐88‐1‐2‐1, Pusa‐44, Pusa‐834, Jaya, and Pusa‐677). Isotopic ally exchangeable Zn (labile Zn) was recorded higher in Typic Ustrochrept of Pabra soil, and uptake of Zn by rice cultivars was also higher in this soil. The kinetic parameters such as maximum influx at high concentrations (I_max) and nutrient concentration in solution where influx is one half of I_max (K_m) behaved differentially with respect to varieties. The highest I_max value recorded was 9.2×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate for Pusa‐933‐87‐1‐11‐88‐1‐2‐1, and the same was lowest for Pusa‐44, being 4.6×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate. The K_m value was highest for Pusa‐44 (2.1×10^?4µmol cm^?2 s^?1) and lowest for Pusa‐933‐87‐1‐11‐88‐1‐2‐1 (1.20×10^?4µmol cm^?2 s^?1). The availability of Zn to rice cultivars in Typic Ustrochrepts of Bhuna and Delhi soils, which are characterized by higher activation energy and entropy factor, was accompanied by breakage of bonds or by significant structural changes.     

河岸带土壤溶解性有机质垂直分布特征及其性质研究

河岸带有机质（Soil organic matter,SOM）的迁移转化在有机碳从陆地生态系统向水域生态系统中迁移转化及污染物的迁移转化中起到了重要的作用。以崇明岛典型河岸带为研究对象,分析了不同区域河岸带土壤有机碳（Soil organic carbon,SOC）、土壤溶解性有机碳（Soil dissolved organic carbon,SDOC）垂直分布特征和三维荧光光谱（Excitation—Emission matrix,EEM）特征,探讨了河岸带对土壤溶解性有机质（Soil dissolved organic matter,SDOM）性质及其潜在环境影响。结果表明：表层土壤（0—30cm）SOC储量占采样深度土壤SOC的40％左右,SDOC占SOC的5％左右,从陆上区域到缓冲区域表层土壤SDOC呈累积效应。河岸带有机质主要来自河岸带植物残体及其代谢产物,地下水也可能是河岸带土壤DOM的另一来源,河岸带土壤中大部分类腐殖质被表层矿物质所吸附。在土壤系统中,综合应用荧光指纹指数[荧光指数（Fluorescence index,FI）,生源指数（The index of recent autochthonous contribution,BIX）和腐殖化指数（Humification index,HIX）]可以有效地揭示其来源和特性,但在土壤体系中单独应用指纹指数需审慎。     

Comparison of Analytical Methods for Organic Matter in Composts and Organic Mulches

Abstract

The conventional dichromate (Walkley and Black), carbon analyzer, and weight loss‐on‐ignition (WLOI) methods are compared for determination of organic matter contents in composts and organic mulches. The objective of this study was to evaluate these three methods for their reliability in determining the organic matter contents of composts and organic mulches that also contain inorganic carbon. The carbon analyzer method overestimated organic matter contents for samples containing inorganic carbon (C) as carbonate or charcoal C. The removal of inorganic C improved the correlation coefficients (r) of results obtained by the carbon analyzer method and the Walkley and Black method (0.95 vs. 0.89). The WLOI method produced results more similar to those obtained with the Walkley and Black method than with a carbon analyzer. Oven drying samples for 16–24 h at 105°C as a basal temperature for WLOI improved results compared with a basal temperature at 70°C, which is commonly used. A heating temperature of 500°C for 12 h resulted in organic matter determinations by the WLOI method in the closest agreement with those obtained by the Walkley and Black method.     

Effect of Oxalic and Citric Acids on Zinc Release Kinetic in Two Calcareous Soils

Rate of zinc (Zn) release from solid to solution phase by organic acids can influence Zn availability in calcareous soils. The objective of the present study was to investigate the effect of different concentrations (1.1, 2.2, and 3.3 mM) of oxalic acid and citric acid on the kinetic release of Zn from two calcareous soils from Eastern Iran. The two organic acids showed significant difference in Zn release from studied soils. Cumulative Zn release during 72 h ranged from 5.85 to 10.4 mg kg^?1 in soil 1 and ranged from 8.7 to 16.9 mg kg^?1 in soil 2 using different concentrations of oxalic acid. The amount of cumulative Zn release after 72 h in soil 1 ranged from 13.65 to 28.77 mg kg^?1 and from 17.63 to 23.13 mg kg^?1 when different concentrations of citric acid was used. In general, Citric acid released 38% more Zn from soils than oxalic acid. The release of Zn from soils increased with citric acid concentration but decreased with increasing of oxalic acid concentrations in the solution. The simplified Elovich equation best described Zn release as a function of time (r² = 0.93 and SE = 0.78). From the present study, Zn release from soils can be limited by the higher concentration of oxalic acid, while citric acid is suitable for enhancing soil lability of Zn.