The determination of hot‐water‐soluble boron in some acid Oregon soils using a modified azomethine‐H procedure

Abstract

A method is proposed for determination of hot‐water‐soluble boron in acid soils from western Oregon. The soil sample is boiled in 0.02 M CaCl₂, filtered, and B determined using azomethine‐H. Soils extracted in this way yielded extracts with little color in them and the predicted error due to this color was 0.00–0.07 ppm B. The use of charcoal as a decolorizing agent resulted in comparatively high predicted errors.

Inductively‐coupled plasma emission spectroscopic (ICP) analysis of distilled water and 0.02 M CaCl₂ extracts indicated that the extractable B level was not affected by the presence of CaCl₂. Azomethine‐H yielded comparable values to ICP but the curcumin method tended to give high values for hot‐water‐soluble B.     

Comparison of a hot water and cold 0.01 M Cacl2 extraction procedures for the determination of boron in soil

Abstract

In 100 different soils, hot (100C) water extractable boron was determined and the results were compared with boron data after extraction of the same soil samples with cold (20C) 0.01 M CaCl₂. Since the boron concentrations in cold soil extracts are too low for direct determination, the extracted boron was converted into BF4‐ and subsequently extracted with a liquid anion exchanger, Aliquat 336, into xylene, and measured by ICP‐AES. A linear relation with R² = 0.74 was found between the two tested procedures. It is, therefore, concluded that with a cold 0.01 M CaCl₂ extraction equally valuable soil boron values can be obtained as with the more difficult to standardize hot water extraction procedure.     

Fractionation and colorimetric determination of boron in soils

We attempted to modify and evaluate existing sequential fractionation schemes for B involving the use of chemicals, which subsequently do not interfere with the measurement of B by colorimetry. Also evaluated was the contribution of various soil B fractions to the amount of B extracted by hot CaCl₂, CaCl₂‐mannitol, salicylic acid, ammonium acetate, HCl, and tartaric acid. For this purpose, 17 soils with diverse properties were used. The extraction scheme proposed here partitioned B into five pools, (i) readily soluble, (ii) specifically adsorbed, (iii) oxide bound, (iv) organically bound, and (v) residual boron, respectively extracted with 0.01 M CaCl₂, 0.05 M KH₂PO₄, 0.175 M NH4‐oxalate (pH 3.25), 0.5 M NaOH, and HF + H₂SO₄ + HClO₄. The procedure of elimination of color from extracts of oxide bound, organically bound, and residual B fractions was also evolved. Relationships of individual B fractions with physicochemical properties of the experimental soils confirmed the general validity of the proposed fractionation scheme. The relationships of different B fractions with extractable B in soils suggest that hot CaCl₂ and salicylic acid may be better extractants for available B in soils.     

The Determination of Soil Boron Fractions,Their Relationships to Soil Properties and the Availability to Olive (Olea europea L.) Trees

This study was conducted to investigate the various boron fractions in olive tree grown soils. The correlations between boron fractions in leaves, fruits and soil properties were examined. For this purpose cv “Gemlik” olive (Olea europaea L.) orchards were visited. Soil samples from 0–30 cm and 30–60 cm deep, the leaf and fruit samples were collected. The greatest proportion of total soil boron is present in residual form (85–88%). It is followed by organically bound B (2.84–4.50%), specifically adsorbed on soil colloid surfaces (0.93–1.31%), oxides (manganese oxyhydroxides, amorphous Fe and Al oxides, crystalline Fe and Al oxides) bound B (7.27–8.31%). The smallest one readily soluble (extracting plant available) boron values were composed of only 0.40–0.50% of total boron ranging. To determine readily soluble boron five different extraction solutions were in the order Hot water ? 0.01 M CaCl₂ ? 1 M NH₄OAc ? 0.1 M KCl ? 0.005 M DTPA. Fruit boron concentration and soil boron fractions showed close correlations than leaf boron concentration.     

A procedure for the determination of soluble boron in soils ranging widely in boron concentrations,sodicity, and pH.

Abstract

Soils in southern Australia within the Mediterranean‐type climate zone vary widely in boron concentrations, from potentially deficient to toxic for plant growth. A general method is needed for the determination of boron in soils ranging from acidic to alkaline, with wide ranges of clay content and sodicity.

The amounts of boron extracted were compared following boiling in 0.01M CaCl₂ in test tubes in temperature‐controlled programmable digestion blocks, or in Erienmeyer flasks on hot plates under different analytical conditions. Comparisons were also made between CaCl₂, hot water, and mannitol extractable boron. All analyses of boron were made by inductively coupled plasma spectrometry (ICPS).

The extraction of boron was dependent on extraction time and temperature of the heating block. Addition of 20 ml of 0.01M CaCl₂ to 10g of soil in 250 ml test tubes fitted with air condensers and placed in a pre‐heated temperature‐controlled digestion block set at 140°C and boiled for 30 minutes. This method was found to be a suitable extractant of boron in soils with a wide range of sodicity, pH and extractable boron (from concentrations potentially deficient to toxic for plant growth).     

Methods of assessing boron availability to kiwifruit plants growing on high boron soils

Abstract

Five soil boron (B) extraction methods were evaluated for their ability to predict available B to kiwifruit plants in soils with high B concentration. The methods were hot water soluble (Hws‐B), 0.05M mannitol in 0.01M calcium chloride (CaCl₂ extractable (Man‐B), 0.05M hydrochloride acid (HCl) soluble (HC1‐B), resin extractable (Resin‐B), and saturation extract (Sat‐B). The amounts of B recovered by the first four methods investigated were strongly correlated with each other, the highest correlation obtained being between Hws‐B and HC1‐B. Plant B was highly correlated to the B recovered by the first four extractants and poorly correlated to the B determined by the saturation method. Soil B concentrations corresponding with B toxicity in kiwifruit are 0.51, 0.80, 0.18, and 2.0 μg‐g^‐1 soil for Hws‐B, Man‐B, HC1‐B, and Res‐B, respectively. The coefficients of determination in some cases were improved when in the regression equations, soil pH and clay content were included.     

Extraction of boron from soil by microwave heating for ICP‐AES determination

Abstract

Extraction with hot water is the most widely used procedure to determine boron (B) in soils for the diagnosis of the nutrient availability for plants. However, this procedure is tedious for routine conditions and requires some special precautions. An alternative extraction procedure was developed, consisting in the extraction of B with a 1.25 g/L solution of barium chloride (BaCl₂) or with water heated in a domestic microwave oven. Boron was determined either by inductively coupled argon plasma emission spectrometry (ICP‐AES) and by spectrophotometry with azomethine‐H. Good correlations were found between the extraction by boiling water under reflux and the extraction by the microwave heating for 13 Brazilian soils, and the contents of B obtained by spectrophotometry did not differ significantly from those obtained by ICP‐AES. Considering the calculated standard deviations, it can be concluded that microwave heating followed by ICP‐AES determination is an adequate procedure for the determination of hot water extractable B in soils.     

Remediation of Lead Contaminated Soil by EDTA. I. Batch and Column Studies

Extraction using ethylenediaminetetraacetic acid (EDTA), and other chelates has been demonstrated to be an effective method of removal of Pb from many contaminated soils. However, column leaching of Pb from alkaline soils with EDTA has been problematic due to extremely low soil permeability. The first purpose of this study was to develop batch extraction procedures and methods of analysis of batch extraction data to provide Pb solubility information which can be used to model the column extraction of Pb from soils. The second purpose was to determine the effect of the addition of KOH and CaCl₂ to K₂H₂EDTA extract solution on both hydraulic conductivity and Pb removal. A Pb-contaminated soil sample was collected from an abandoned battery recycling facility. Both batch shaker extractions and column leaching experiments were completed using 5 different EDTA extract solutions. When only CaCl₂ was added to EDTA no change in the amount of Pb removed by batch extraction was observed. As expected, lead solubility was observed to decrease as pH was increased by the addition of KOH. However, Pb solubility was only slightly decreased by the addition of both CaCl₂ and KOH. The amount of time required to leach 6.0 L of extraction solution through the soil columns varied from 2 to 33 days. The addition of CaCl₂ and/or KOH resulted in increased soil hydraulic conductivity relative to the EDTA-only solution. The hydraulic conductivity was related to residual calcium carbonate content, suggesting that dissolution of CaCO₃ and subsequent production of CO₂ gas in the soil pores was partially responsible for the observed reductions in soil permeability. However, Pb removal was diminished with the addition of CaCl₂ and KOH because of the decreased Pb solubility and also kinetic limitations associated with the shorter residence time of the extract solution in the column.     

Determining critical limit of boron in soil for wheat (Triticum aestivum L.)

Abstract

Critical values of boron (B) for wheat nutrition in soil and plant were determined through a pot experiment with twenty-one surface soils of Alluvial flood plain and Red-latertic belt comprising three major soil orders (Entisols, Alfisols, Inceptisols) with four levels of boron. Application of boron significantly increased the dry matter yield as well as uptake of B by plants. Critical concentration of hot calcium chloride (CaCl₂) extractable B in soil for wheat was found to be 0.53?mg?kg^?1. The critical plant B concentration varied with growth stages and values were 7.4?mg?kg^?1 at panicle initiation and 4.18?mg?kg^?1 at maturity, respectively. The findings of this investigation also recommend the application of 2?kg?B^?1?ha^?1 for ensuring B sufficiency to wheat in Indo-gangetic alluvial and Red-Lateritic soils.     

Availability of extractable boron in some acid soils,west Bengal,India

Abstract

A relatively small range between deficiency and toxic limits of boron (B) necessitates precise evaluation of the availability of extractable boron before applying B in deficient soils. Keeping this in view, laboratory and greenhouse experiments were conducted to assess the availability of native B in soils. For this purpose, 25 acid soils with diverse properties and varying hot water extractable B content, were selected from lateritic and alluvial tracts of Southern West Bengal. A greenhouse pot experiment with four rates of B (0, 0.5, 1.0, and 2.0 mg kg^‐1) was conducted in completely randomized design to study the response of soybean (Glycine max L.) to native and applied B in all 25 soils. The suitability of nine extractants for determining available soil B was assessed by correlating the amount of extractable B in untreated soils with Bray's percent yield, uptake, and tissue B concentration of soybean plants. Optimization of salicylic acid concentration is described and the advantages of this extractant are discussed. The interference of amethyst color (produced by iron and salicylic acid) with the colorimetric estimation of B is studied. Hot CaCl₂ was found to be the most suitable extractant for the determination of available B in these soils, followed by hot water, salicylic acid, and ammonium acetate. However, salicylic acid appeared to be the most efficient extractant for routine soil analysis for available B, where a large number of samples are analyzed. The critical values in respect to sufficiency of extractable B for soybean plants were 0.51 for hot water, 0.61 for hot CaCl₂, 0.27 for ammonium acetate and 0.45 mg kg^‐1 for salicylic acid. The critical B concentration in soybean plants was 18 mg kg^‐1 on dry weight basis. Multiple regression equations relating soil properties to native soil B extracted by various extractante were developed. It was observed that organic carbon and clay contributed positively to B extracted by hot water, hot CaCl₂, and ammonium acetate, while salicylic acid extractable B showed positive relationships with cation exchange capacity (CEC) and clay. The CEC and Fe₂O₃ were found to have positive influence on tartaric acid extractable B. Implications of the influences of soil properties on the extractable B content of soils are discussed.     

Plant availability of boron in acid soils as assessed by different extractants

Estimation of available‐boron (B) status through conventional methods in B‐deficient acidic Inceptisols and Entisols is often hampered because of their very low B content. In the present study, the extractability of available B by different extractants was tested in relation to soil properties. Plant availability of B was assessed with mustard (Brassica campestris L.) and wheat (Triticum aestivum L.) in pot experiments. Twelve soils with varying characteristics were extracted for available B with hot water (HW), hot CaCl₂ (HCC), KH₂PO₄ (PDP), tartaric acid (TA), and mannitol‐CaCl₂ (MCC). Mustard (cv. B‐9) and wheat (cv. PBW‐343) were grown with four levels of B (0, 0.25, 0.50, and 1.0 mg [kg soil]^–1). Dry‐matter accumulation and B concentrations were determined at pre‐flowering and full‐maturity stages for mustard and at panicle‐initiation and maturity stages for wheat. The extraction of B from the soils ranked HCC > HW > PDP > TA > MCC. The higher extractability with HW and HCC was likely due to higher temperature and that of PDP because of its phosphorus content, which facilitated the desorption of B. The low B extraction with MCC resulted from the poor mannitol‐B complex formation in acidic soils. The application of B increased dry‐matter accumulation, plant B concentration, and uptake at all B levels and growth stages in both crops with the responses being more pronounced during the early developmental stage. Based on linear correlations, Mallow's Cp statistics, and principal‐component analyses, HCC and HW were the best extractants for estimating available B in the acidic experimental soils.     

Soil analysis procedures using 0.01 M calcium chloride as extraction reagent

Abstract

This publication gives details of laboratory procedures for the determinations of bioavailable (e.g., plants) quantities of nutritional and polluting inorganic elements in 0.01 M CaCl₂ extracts of air‐dry soil samples. Air‐day soil samples are extracted for two hours with a 0.01 M CaCl₂ solution of 20°C in a 1:10 extraction ratio (W/V). After measuring the pH in the settling suspension, the concentrations of nutritional and polluting elements are measured in the clear centrifugate or filtrate. The procedure is simple, easy to perform, and cheap (labor, chemicals) in daily use in routine soil laboratories. The method receives internationally more and more attention as an alternative for the many extraction procedures for a single nutrient or pollutant that are still in use nowadays. The soil is extracted with a solution what has more or less the same ionic strength as the average salt concentration in many soil solutions. Various nutrients and metals can be measured in a single extract that allows considering relationships between them during interpretation of the data. For most elements, different detection techniques are described in detail in this publication. Detailed laboratory procedures are described for the determination of pH, total dissolved organic carbon, nitrate, ammonium, total dissolved nitrogen, sulphate, total dissolved sulfur, ortho‐phosphate, total dissolved phosphate, sodium, potassium, magnesium, cadmium, copper, nickel, lead, aluminum, iron, arsenic, boron, and phenols. Since only one extract of soil samples is used, profitable use can be made of multi‐element detection techniques like segmented‐flow analysis spectrometry, ICP‐OES, and ICP‐MS.     

Chloroform-labile trace elements in soil via fumigation-extraction: Steps towards the soil microbial ionome beyond C:N:P

Secondary and trace elements may be limiting soil microbial functioning, albeit microbial demand and content remain largely unknown and methods for their in situ detection are limited. Thus, the objective of the present study was to take the first step towards the method development for the assessment of the soil microbial ionome, that is, the elemental composition of soil microbial communities. Chloroform (CHCl₃) fumigation extraction was used for the detection of microbial CHCl₃-labile secondary and trace element concentrations in soils. The suitability of two extractants (NH₄NO₃, CaCl₂) for the quantification of CHCl₃-labile concentrations of phosphorus, sulphur, potassium, sodium, and magnesium, as well as selenium, iron, zinc, manganese, copper, cobalt, nickel, molybdenum, vanadium, boron, silicon, barium, arsenic, and cadmium, were tested in six agricultural soils. Additionally, three soil to extractant ratios (1:5, 1:10, and 1:20) and two extraction durations, 1 or 2 h, were tested in a subset of two soils. Out of the two extractants tested, 0.01 M CaCl₂ was found to be the best-suited extractant. For CaCl₂, a soil-to-extractant ratio of 1:20 with an extraction time of 1 h was best for the majority of elements in the two soils tested. In a limited number of agricultural soils, we were able to show that CHCl₃ fumigation extraction can successfully be applied to the elements phosphorus, sulphur, potassium, sodium, magnesium, zinc, manganese, copper, nickel, vanadium, boron, silicon, and barium to yield a CHCl₃-labile element fraction. Conversion values to microbial biomass, accounting for elements contained in the cell envelope components, which are mostly not extractable, and to account for adsorption to soil colloids during extraction are yet to be determined in a larger variety of soils. To overcome some of the limitations of the fumigation extraction approach for secondary and trace elements, a pre-extraction step may provide a suitable solution.     

Impact of black carbon addition to soil on the determination of soil microbial biomass by fumigation extraction

The efficiency of the fumigation extraction method on the determination of soil microbial biomass carbon and ninhydrin-N was tested in three different soils (UK grassland, UK arable, Chinese arable) amended with black carbon (biochar or activated charcoal). Addition of activated charcoal to soil resulted in a significant decrease in K₂SO₄ extractable carbon and ninhydrin-N in all three soils, whereas the addition of biochar generally did not. A lower concentration of the extraction reagent (0.05 M vs. 0.5 M K₂SO₄) resulted in a significantly lower extraction efficiency in the grassland soil. The extraction efficiency of organic carbon was more affected by black carbon than that of ninhydrin-N, which resulted in a decreased biomass C/ninhydrin-N ratio. The impact of black carbon on the extraction efficiency of soil microbial biomass depended on the type of black carbon, on the concentration of the extraction medium and on soil type.     

Applicability of 0.01 M CaCl2 as a single extraction solution for the assessment of the nutrient status of soils and other diagnostic purposes

Abstract

The applicability of 0.01 M CaCl₂ solution as a single extraction agent for soils as a basis for fertilizer recommendation was tested on a variety of soils both from the Netherlands and from some tropical countries. Air‐dry soil samples were subjected to extraction with 0.01 M CaCl₂ and to several conventional extraction procedures, and the results were compared. In the soil suspensions pH was measured, whereas in the extracts Na, K, Mg, P, different extractable N‐forms and Zn were measured. The values found in CaCl₂ extracts are discussed in relation to results of other extraction procedures and as to their potential value in soil quality assessment. It is concluded that a single extraction procedure with 0.01 M CaCl₂ can be applied for fertilizer recommendation purposes. The possibility of determining different extractable N‐forms (NH₄, NO₃, soluble organic N) significantly enhances the value of the method in predicting the N‐fertilizer needs. Furthermore it was found that the concentration of Zn in 0.01 M CaCl₂ extracts was a good indicator of phytotoxicity in a polluted area. Additional advantages of this extraction are low costs, simplicity and repro‐ducibility.     

Use of Reference Soils in Determinations of 0.01 M Calcium Chloride Available Metals

There are few readily available standard reference soils for which 0.01 M calcium chloride (CaCl₂) soil extraction available metals data are available. This study assessed the ease with which new available metals data could be generated for reference soils. Data on 0.01 M CaCl₂ available elements for four reference soils from the Wageningen Evaluating Programs for Analytical Laboratories and three reference soils from the Australasian Soil and Plant Analysis Council proficiency testing program are presented. It is difficult to generate new 0.01 M CaCl₂ available metal values for standard reference soils, because trace element concentrations are low and measurements have relatively high variability. We suggest that laboratories can use reference soils as quality control samples in the analysis of 0.01 M CaCl₂ available metals by reporting recoveries for major elements (e.g., potassium [K], magnesium [Mg], and sodium [Na], for which reference values are of high reliability) to provide assurance of acceptable extraction efficiency.     

Effect of some soil properties on extractable boron content in argentine pampas soils

Abstract

The influence of some soil properties on hot 0.02 M calcium chloride (CaCl₂) extractable boron in the Argentine Pampas was studied. The selected soils represent an extensive area in the middle west of the country where most of the grain crops are produced. Soils have all developed on loess and cover a wide range of organic matter, pH, and exchangeable calcium. The most representative soils are Typic Argiudolls and Typic Haplustolls. Two hundred soil samples were taken in order to characterize their 0.02 M CaCl₂ extractable boron content and study the boron behavior with regard to other soils properties and environmental conditions. The amounts of extracted boron on all samples had a significant correlation with soil organic carbon (positive), and soil pH (negative). The regression equation between extractable boron and organic carbon content was y=0.1021+0.3722 OC R²: 0.51. Since solubility in hot CaCl₂, 0,02 M is considered an availability index, these results support the hypothesis that organic carbon content is the main boron reserve for plants. When a multiple regression was calculated, both variables organic carbon and pH explained 57% of variation in extractable boron. The studied area can be subdivided into regions with different boron content, within each region the relationship between boron content and organic carbon and pH were also different. The exchangeable calcium content had a light influence especially in the subsuperficial layer. The influence of environmental conditions on boron content and its relationship with soil properties were discussed.     

Evaluation of a Suitable Extractant and Determination of Critical Limit of Boron in Soil and Mustard (Brassica Juncea L.) Plant by Various Extractants in Inceptisols of Varanasi

Pot culture experiment was conducted to evaluate the suitability of extractants and to determine the critical limit of boron (B) in soil and mustard plant in Inceptisols of Varanasi. Twenty-one bulk soil collected from different locations were used for growing mustard. Five extractants, namely hot water, hot 0.01molar (M) calcium chloride (CaCl₂), 0.01M CaCl₂ + 0.05 M mannitol, 1.0 M ammonium acetate (NH₄OAC) and 0.05 M hydrochloric acid (HCl), were assessed by correlating the amount of extractable B in untreated and B fertilizer-treated soil with Bray’s per cent yield, plant tissue B concentration and B uptake by mustard. Similarly, correlation coefficients of the B extracted by different extractants and soil properties were calculated. The suitability of B extracted by different extractants was in the order of hot 0.01M CaCl₂ (HCC-B) > hot water (HW-B) > 1.0 M NH₄OAC (AA-B) > 0.05M HCl (HA-B) > 0.01M CaCl₂ + 0.05M mannitol (CCM-B). The critical limits of extractable B in soil as determined by the graphical procedure were 0.54, 0.60, 0.36, 0.45 and 0.45 mg kg^?1 and the statistical procedures were 0.54, 0.60, 0.38, 0.46 and 0.48 mg kg^?1 with HW-B, HCC-B, CCM-B, AA-B and HA-B, respectively. Soil containing available B below the critical limit responded to B fertilization.     

Determination of Zinc Phytoavailability in Soil by Diffusive Gradients in Thin Films

Assessment of zinc (Zn) phytoavailability by the newly developed technique of diffusive gradients in thin films (DGT) has started gaining more importance because of some advantages over routine soil extractants. A greenhouse study was conducted to determine Zn phytotoxicity thresholds and the phytoavailability of Zn to sorghum sudan (Sorghum vulgare var. sudanese) grass by DGT, compared with calcium chloride (CaCl₂) extraction. Treatments were five Zn levels and two soil pH (6.5 and 6). To obtain various amounts of Zn phytoavailability, soils having two different pH values were amended with zinc sulfate (ZnSO₄) at rates of 0, 150, 300, 600, and 1200 mg Zn kg^?1. Control soil (pH = 6.5) was treated with predetermined elemental sulfur to create different soil pH values (6). Shoot and root Zn concentrations ranged from 27 to 827 mg kg^?1 and 101 to 2858 mg kg^?1, respectively. In general, the Zn concentrations in shoots and roots were increased by increasing Zn concentrations and soil pH. Increasing applied Zn to soil decreased the plant biomass yield and increased adsorption of Zn by DGT. Calcium (Ca) to Zn ratios for all treatments except controls were <26 for shoots and <13 for roots. The CaCl₂‐extractable Zn and effective concentration (C_E) correlated well with plant Zn concentration. A critical shoot Zn concentration for 90% of the control yield was chosen as an indicator of Zn toxicity. The performance of DGT, CaCl₂ extraction, Ca/Zn ratio and plant Zn concentrations were similar for assessing Zn phytoavailability.     

Irrigation with brackish water modifies the boron requirement of mungbean (Vigna radiata L.) on typic calciargid

The boron (B) sufficiency range for plant growth is narrow and its management is problematic under brackish irrigation water. This study was conducted to evaluate the B requirement of mungbean at different sodium adsorption ratios of irrigation waters (SAR_iw) [control, 8 and 16 (mmol_c L^?1)^1/2]. The boron adsorption characteristics of a loamy soil were first determined in the laboratory by equilibrating 2.5 g soil with 0.01 M CaCl₂ solution containing different B levels. Boron rates for a pot study were computed against different soil solution levels by fitting sorption data in a modified Freundlich model [x/m = K _f (EBC)^1/n ]. The maximum increase in shoot dry matter was 11.9% when B was applied at 1.29 mg kg^?1 soil at control SAR_iw. Visual leaf B toxicity symptoms appeared at higher B rates and became severe at higher SAR_iw. By contrast to Ca, shoot concentrations of B and Na increased significantly with B application and SAR_iw. For optimum shoot growth, internal and external B requirements were 25 mg B kg^?1 shoot dry matter and 0.39 mg B L^?1 soil solution, respectively, at control SAR_iw. At higher SAR_iw, a lower concentration of B in plant shoots and soil solution had an inhibitory effect on plant growth.