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).     

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.     

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.     

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.     

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.     

Extraction of soil boron for predicting its availability to plants

Abstract

Field and greenhouse studies were conducted in Prince Edward Island (P.E.I.) on soybean (Glycine max (L.) Merr.), red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and rutabaga (Brassica napobrassica, Mill). Plant B concentrations were compared to soil B extracted by hot water, 0.05M HCl, 1.5M CH₃COOH, and 0.01M CaCl₂. The r values for extractable soil B versus plant B were: hot water (0.67), 0.05M HCl (0.82), 1.5M CH₃COOH (0.78), and hot 0.01M CaCl₂(0.61). Results of soil B from the 0.05M HCl extracts were generally found to give the best correlation and linear regression among the four extractants tested for predicting the B availability to plants. Overall, the 0.05M HCl proved to be the best extractant and is recommended for predicting the available B status of acid soils. The probability of error with 0.05M HCl is less since it is shaken for a fixed period of time as opposed to subjective error which could be introduced in monitoring the boiling time using hot water. Since HCl is the cheapest among the chemical extractants used it would be most suited for determining soil B in countries with poor economic resources.     

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.     

Extraction of water‐soluble organic matter from mineral horizons of forest soils

Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H₂O, 0.01 M CaCl₂, and 0.5 M K₂SO₄. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K₂SO₄ extracted the largest amounts of WSOC (up to 126 mg C kg^–1) followed by H₂O followed by CaCl₂. The H₂O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol^–1 cm^–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K₂SO₄ bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.     

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.     

Addition of phosphorus to soils with low to medium phosphorus retention capacities. II. effect on soil phosphorus extractability

Abstract

Knowledge of the change in soil extractable phosphorus (P) as a consequence of soil P fertilization could be useful in discriminating soils with a potential for soil P release to runoff or movement of P along the soil profile. In this research, soils with low to medium P retention capacity were equilibrated for 90 days with soluble P (KH₂PO₄) at rate of 100 mg P kg^‐1 soil. After this period, soil samples both with and without the P addition were analyzed using six conventional methods: 1) Olsen, 2) Bray 1,3) Mehlich3,4) Egner, 5) Houba, dilute CaCl₂ solution, and 6) distilled water, and three “innovative”; P‐sink methodologies: 1) Fe oxide‐coated paper strip, 2) anion exchange resin membrane, and 3) cation‐anion exchange resin membrane. The soils without P addition had low levels of extracted P as determined by all nine procedures. Net increases in the amount of P extracted from the soils with added P ranged from 4.2 mg kg^‐1 (CaCl₂ extraction) to 57.6 mg kg^‐1 (cation‐anion resin membrane extraction). Relationships between change in extracted P and i) physical and chemical characteristics, and ii) soil P sorption properties are also presented and discussed.     

Effect of CaCl2 on the kinetics of dissolved organic matter release from a sandy soil�

The dissolution of organic matter in soil is of fundamental relevance for the fate of organic contaminants associated with organic matter and for the microbial availability of organic matter. In this study, the kinetics of soil organic matter (SOM) dissolution from a sandy forest soil was investigated under different electrolyte conditions, using a continuous extraction method. The mathematical analysis of the concentration signal obtained from extractions with constant flow rates and after sudden flow rate changes showed that the dissolution of SOM is diffusion limited. The dissolution rate was lower during extraction with 0.01 M CaCl₂. The reaction on sudden flow rate changes was slower when extracting with 0.01 M CaCl₂ as compared to water, and the mechanism was different. These observations were explained by a gel phase developing in the swelling SOM. The lower dissolution rates found for extractions with 0.01 M CaCl₂ could indicate a more stable gel structure in the presence Ca²⁺. The development of the gel phase may be influenced by mechanical strain due to increased flow rates.     

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.     

Sources of variation in hot water extraction and colorimetric determination of soil boron

Abstract

The reliability of the soil test for boron (B) has been questioned in recent years. Two studies were initiated to identify some of the sources of variability in the extraction and analysis phases of the B soil test. The first study evaluated the influence of reflux and cooling times (10,20,30 min.) on B values. The second study investigated the effectiveness of CaCl₂ (0,3,6,9 mM) and charcoal (0,0.08, 0.16, 0.32, 0.64 g) as soil extract decolorizing agents. Hot water extraction, in plastic pouches, with azomethine‐H and/or ICP analysis was used to determine soil B. Increasing reflux time resulted in significantly higher B values, while increasing cooling time resulted in significantly lower B values (P = 0.05). Standardized refluxing/cooling conditions contributed to improved reprodudbility of B values obtained by hot water extraction. Increasing reflux CaCl₂ concentration and/or charcoal addition significantly lowered B values. The lower B values obtained with the CaCl₂ treatments were the direct result of decreased background color. Charcoal was also effective in reducing background color but higher additions of charcoal (greater than 0.16 g) resulted in excessive sorption of boron. Soils should be refluxed in 10 mM CaCl₂ to minimize extract color if azomethine‐H analysis is used. If extract color persists, a minimum addition (less than 0.16 g) of charcoal should be added prior to filtering. The conclusions of this study were incorporated into a soil test B procedure included in this report.     

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.     

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.     

Change Point in Phosphorus Release from Variously Managed Soils with Contrasting Properties

Abstract

Investigating the relation between concentration or release of phosphorus (P) into soil solution (CaCl₂‐P, determined by 0.01 M CaCl₂ extraction of soils) and soil test phosphorus (Olsen P, or 0.5 N NaHCO₃‐extractable soil phosphorus) for 10 widely ranging and variously managed soils from central Italy, a change point was evident where the slopes of two linear relationships meet. In other words, it was possible to distinguish two sections of the plots of CaCl₂‐P against Olsen P, for which increases of CaCl₂‐P per unit of soil test P increase were significantly (p<0.05) greater above than below these change points. Values of change point ranged from 14.8 to 253.1 mg kg^?1 Olsen P and were very closely correlated (p<0.001) to phosphorus sorption capacity of soils. Similar change points were also previously observed when Olsen P (and also Mehlich 3 P) of surface soils was related to the P concentration of surface runoff and subsurface drainage. Because insufficient data are available relating P in surface soils and amount of P loss by overland, subsurface, or drainage flow, using the CaCl₂ extraction of soil can be convenient to determine a change point in soil test P, which may be used in support of agricultural and environmental P management.     

Extractability of labelled microbial biomass N by electro-ultrafiltration and CaCl2 extraction

A laboratory soil incubation and a pot experiment with ryegrass were carried out in order to examine the extractability of microbial biomass N by using either 10-mM CaCl₂ extraction or the electro-ultrafiltration (EUF) method. The aim of the experiment was to test the hypothesis whether the organic N (Norg) extracted by EUF or CaCl₂ from dried soil samples represents a part of the microbial biomass. For the laboratory incubation a ¹⁵N-labelled Escherichia coli suspension was mixed with the soil. For the pot experiment a suspension of ¹⁵N-labelled bacteria was applied which had previously been isolated from the soil used. Soil samples of both treatments, with and without applied bacterial suspension, were extracted by EUF and CaCl₂. The extractability of applied microbial biomass was estimated from the difference in extractable Norg between the two treatments. In addition, the N isotopic composition in the upper plant matter, in the soil, and in organic and inorganic N fractions of EUF and CaCl₂ extracts was analysed. Both experiments showed that the applied microbial biomass was highly accessible to mineralization and thus represented potentially mineralizable N. However, this mineralizable N was not extractable by CaCl₂ or by the EUF method. It was, therefore, concluded that the organic N released on soil drying and which was thus extractable was derived from the non-biomass soil organic matter. The result suggests that both extraction methods may provide a suitable index for mineralizable N only in cases where the decomposable organic substrates are derived mainly from sources other than the living soil biota.Dedicated to Professor J. C. G. Ottow on the occasion of his 60th birthday     

A new soil test method for the determination of plant‐available cadmium in soils

Abstract

A new soil test procedure using 1M NH₄Cl was developed for the extraction of plant‐available cadmium (Cd) from soils. Five grams of soil is weighed into a 50‐mL polyethylene vial to which 30 mL of 1M NH₄Cl solution is added. The soil suspension is then shaken on a horizontal shaker for 16 h at 25°C at 180 cycles per min. The suspension is then centrifuged at 2,500g for 5 min and the supernatant filtered through a 0.45 μm nitrocellulose filter under vacuum. Cadmium in the extract is then determined at 228.8 nm on a graphite furnace equipped atomic absorption spectrophotometer. A highly significant correlation was observed between the natural logarithm (In) of 1M NH₄Cl‐extractable Cd in soils and the Cd content in the grain of durum wheat (Triticum turgidum var. durutn L.) grown on the same soils (r = 0.974, p = 3.8 x 10^‐7). In comparison with several commonly used extradants, such as ABDTPA, CaCl₂, NH₄OAc, and NH₄NO₃, the 1M NH₄Cl‐extracted Cd from soils was found to be a better index of Cd availability.     

Extraction of soil phosphorus with calcium chloride solution for prediction of plant availability

Abstract

Soil and vegetative samples of ley and cereals were collected four times during the growing season from field and pot trials with different phosphorus (P) fertilisation levels. The soil samples, dried and of field moisture condition, respectively, were extracted by 0.01M calcium chloride (CaCl₂) at two different soil:extractant ratios (1:2 and 1:10), and analysed by inductively coupled plasma emission spectrometry (ICP) for content of P. The plant samples were digested in concentrated nitric acid (HNO₃) and the P content determined by ICP. Calcium chloride‐extractable P content was lowest in the middle of the growing season, while plant P was highest in the beginning of the season. Phosphorus extracted by CaCl₂ solution was higher at a soil:extractant ratio of 1:10 than at 1:2, and also when drying the soil before extraction. A soil:extractant ratio of 1:2 minimizes the risk of coming too near the limit of determination. However, if organic soils are also to be included, a ratio of 1:10 has to be used in order not to have all the solution absorbed by some types of soils. The solution of ammonium lactate/acetic acid (AL) extracted nearly two powers of ten more P than CaCl₂ solution. There was a good relationship between the methods. If calcareous or very acid soils had been included, a less good relation would have been expected. Plant P content varied more in straw than in grain between different treatments. Measuring CaCl₂‐extractable P with ICP might be able to predict plant uptake of P by plants. This would be a great advantage when using 0.01M CaCl₂ as a universal extradant.