Extraction with 0.01 m CaCl2 underestimates the concentration of phosphorus in the soil solution

The aim of this paper was to compare the concentration of P in soil extracts prepared with water and a ‘soil solution proxy’ (‘SSP’, that is, a salt solution similar in ionic composition and strength to the actual soil solution) with that in 0.01 m CaCl₂ extracts, which is usually taken as a measure of soil P intensity. Seventy widely ranging agricultural soils from the Mediterranean part of Spain were used. Soil/solution ratio was 1:10 and extraction time 3 days. For 0.01 m CaCl₂, a short extraction time of 30 min was also used as the reference method. CaCl₂‐P(3 days) and CaCl₂‐P(30 min) were not significantly different for the 40 noncalcareous soils group, but CaCl₂‐P(3 days) was significantly larger than CaCl₂‐P(30 min) for the 30 calcareous soils group. The Water‐P/CaCl₂‐P(30 min) ratio was not significantly related to any soil property, its mean being 6.3 for the noncalcareous and 5.8 for the calcareous soils group. The mean SSP‐P/CaCl₂‐P(30 min) ratio was 2.6 for the noncalcareous and 3.1 for the calcareous soils group, and decreased slightly with increasing ionic strength of the soil solution in the noncalcareous soils group. These results are consistent with the promoting influence of the Ca ion and ionic strength on P adsorption by permanent‐charge soils. The fact that extraction with 0.01 m CaCl₂ generally results in underestimation of the actual concentration of P in the soil solution should be considered when CaCl₂‐P is used as a soil P test.     

Ionic strength effect on heavy metal adsorption by soil

Abstract

The adsorption of Cd and Cu by three different soils was studied in the presence of variable concentrations of calcium chloride. Cadmium adsorption fitted the Freundlich equation while Cu better fitted the Langmuir equation. Increasing ionic strength decreased metal adsorption because of the competition of Ca‐ions for the adsorption sites of the soils.

Results could be useful from the standpoint of correct management of sewage sludges and animal slurries applied to agricultural soils because they have an electrolyte concentration greater than that found in normal soil solutions.     

Manganese retention by selected calcareous soils as related to soil properties

Abstract

Calcareous soils often need supplemental manganese (Mn) to support optimum plant growth, but some reports show that the apparent recovery of applied Mn is very low in such soils, i.e., nearly all of the applied Mn is retained in the soil. This experiment was conducted to find the relationship between the retained Mn and selected properties of calcareous soils. Eleven surface (0–20 cm) soil samples with pH ranging from 7.7 to 8.1 and calcium carbonate equivalent (CCE) ranging from 20 to 50% were used in the Mn adsorption study. Two‐gram subsamples of each soil were equilibrated with 20 mL of 0.01M CaCl₂ solutions initially containing 10 to 200 mg Mn L^‐1. The Mn that disappeared from solution (after 6 h shaking at 25°C) was considered as adsorbed (retained) Mn. The adsorption data showed a highly significant fit to Freundlich and also to the two‐surface Langmuir adsorption isotherms. The coefficients of both isotherms showed significant positive correlations with cation exchange capacity (CEC), organic matter (OM), and CCE of the soils indicating that OM and calcium carbonate are the sites of Mn retention in calcareous soils. Comparison of the adsorption data of this experiment with those of plant Mn uptake of the same soils (published earlier) shows that as the Langmuir second surface adsorption maxima (maximum retention capacity) of the soils increase the plant Mn concentration and uptake decrease.     

Competitive and noncompetitive adsorption of silicate and phosphate by two acid Si-deficient soils and their effects on P and Si extractability

The effects of pH on the adsorption of silicate and phosphate, either singly or in competition, by two acid soils were investigated. Both soils adsorbed two to three times more P than Si and adsorption isotherms at pH 5.0, 5.5, 6.0 and 6.5 showed that increasing pH greatly increased Si adsorption but decreased that of P. Silicate adsorption was very low below pH 5.0, increased rapidly up to pH 9–10 before decreasing again. Adsorption of P was at a maximum at pH 2.0, decreased slowly up to pH 7.0 and then more rapidly above pH 7.0. When Si and P were added at equimolar concentrations, the presence of P decreased Si adsorption between pH 6.0 and 8.0 while the presence of Si decreased P adsorption in the pH region 6.0 and 11. Addition of calcium silicate at rates equivalent to 300, 600 and 1200 kg Si ha^?1 resulted in a progressive increase in soil pH. Separate samples of soil were treated with Ca(OH)₂ to give the same pH values so that the effect of Si could be identified. The highest rate of Si (1200 kg ha^?1 which gave a pH of 6.5) caused a significant decrease in P adsorption (as determined by adsorption isotherms) and an increase in resin-extractable P but the lower rates had little effect. Addition of P to the soil as calcium phosphate at rates equivalent to 30, 60 and 100 kg P ha^?1 all caused a decrease in Si adsorption capacity and an increase in CaCl₂-extractable Si. It was concluded that the strategy of adding Si to lower P requirements in acid soils is not likely to be effective while addition of fertilizer P may well lower Si adsorption and promote Si desorption and its increased mobility.     

Wheat P requirements on calcareous moroccan soils: I. A comparison of olsen,soltanpour and CaCl2soil tests

Abstract

Wheat [Triticum aestivum(L.)] is the major cereal crop of the Chaouia (dryland) region of Morocco. Efforts for self‐sufficiency in wheat will require improved fertility management on the calcareous soils of this region. This research was undertaken to evaluate the suitability of five soil P extractors for predicting the need for P fertilization on 15 important soils in this region. The Olsen (0.5MNaHCO³), the Soltanpour (1.0MNH₄HCO₃+ 0.005MDTPA) and their dilution modifications, and CaCl₂solution P method were evaluated in laboratory and greenhouse experiments.

Ten of the 15 soils responded to P fertilization. The five soils for which a significant P response was not measured were from the P plateau of the Chaouia region. The P extractors performed equally to predict the need for P fertilization. The critical levels below which a response would be highly probably and above which no response would be anticipated varied by extractor and method used to interpret the soil test values. A graphic method indicated the critical P values to be: Olsen 10.2, modified Olsen 18.0; Soltanpour 2.0; modified Soltanpour 12.5 and CaCl₂0.20 mg P kg^‐1. A second degree polynomial method indi cated the critical P values to be: Olsen 8.2; modified Olsen 14.0; Soltanpour 1.1; modified Soltanpour 5.1 and CaCl₂0.12 mg P kg^‐1. This limited data will permit the interpretation of soil test values as to whether a response to P fertilization is highly probable for the dominant soils of this wheat region.

Results from this study suggest that any of the five P extractors evaluated could be selected to calibrate P response under field conditions. It might be best to concentrate future research efforts on the Olsen test because most field P calibration data published with similar soils, climate and crops are with this extractor     

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.     

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.     

Effects of phosphate,nitrate and chloride on calcium,magnesium and manganese content of cigar‐wrapper tobacco

Abstract

Nutrient solutions containing three levels of phosphate, nitrate, and chloride were applied to cigar‐wrapper tobacco (Nicotiana tabacum L.) plants growing in sand culture for a period of 18 days. Concentrations of other nutrient elements in the nutrient solutions were held constant and the solutions were applied to pots as needed to maintain favorable moisture conditions for plant growth. Plants were in the two leaf stage when transplanted and were maintained on a single nutrient solution for 38 days before treatments were started. At the end of an eight weeks growing period, plant leaves were harvested and analyzed for Ca, Mg, and Mn. Dry matter yield was significantly (P=0.01) increased when 2 mM/1 of Ca(NO₃)₂ replaced an equivalent amount of Ca(H₂PO₄)₂ or CaCl₂ in the nutrient solution. Nitrate significantly (P=0.05) increased Ca and Mg content and decreased Mn concentration in leaf tissue in comparison to chloride. Calcium and Mg content were significantly (P=0.05) decreased and Mn content of tobacco leaves was increased by phosphate in comparison to nitrate and chloride.     

Speciation and calcium competition effects on cadmium sorption by sandy soil at various pHs

The effects of Ca competition, ionic strength, inorganic complexation and pH on cadmium adsorption by a sandy soil were studied. Sorption of Cd was measured using four different electrolytes CaCl₂, Ca(NO₃)₂, NaNO₃ and NaCl at a constant ionic strength (I) of 0.003 M at three different pHs, at variable Ca/Na ratio with a constant ionic strength of 0.03 and at variable ionic strengths between 0.003 and 0.3 M for two different pHs for Ca(NO₃)₂ and NaNO₃. The measured Cd sorption isotherms were non-linear. In the case of Cl as electrolyte anion, 13% of the Cd in solution is complexed at I= 0.003 (0.002 M Cl) and 91% of Cd is complexed at I= 0.3 (0.2 M Cl). If NO₃ is the anion, none of Cd is complexed at I= 0.003 and 11% at I= 0.3. The Cd complexes do not adsorb significantly. Calcium competition, at an ionic strength of 0.03, reduced the Cd adsorption by 60–80% compared with the case that Na is the cation. Increasing the ionic strength from 0.003 to 0.3 decreased Cd sorption by 60% for Ca(NO₃)₂ and 25% for NaNO₃ due to a decrease of the activity coefficient, increase of inorganic complexation and increase of Ca competition. A decrease of one pH unit reduces Cd sorption of about 75%. Sorption of Cd by soil could be described adequately with the three-species Freundlich (3SF) equation in which pH, complexation, Ca competition and ionic strength effects were taken into account.     

Nickel adsorption in two Oxisols and an Alfisol as affected by pH,nature of the electrolyte,and ionic strength of soil solution

Background, aim, and scope  The retention of potentially toxic metals in highly weathered soils can follow different pathways that variably affect their mobility and availability in the soil–water–plant system. This study aimed to evaluate the effects of pH, nature of electrolyte, and ionic strength of the solution on nickel (Ni) adsorption by two acric Oxisols and a less weathered Alfisol. Materials and methods  The effect of pH on Ni adsorption was evaluated in surface and subsurface samples from a clayey textured Anionic ‘Rhodic’ Acrudox (RA), a sandy-clayey textured Anionic ‘Xantic’ Acrudox (XA), and a heavy clayey textured Rhodic Kandiudalf (RK). All soil samples were equilibrated with the same concentration of Ni solution (5.0 mg L⁻¹) and two electrolyte solutions (CaCl₂ or NaCl) with different ionic strengths (IS) (1.0, 0.1 and 0.01 mol L⁻¹). The pH of each sample set varied from 3 to 10 in order to obtain sorption envelopes. Results and discussion  Ni adsorption increased as the pH increased, reaching its maximum of nearly pH 6. The adsorption was highest in Alfisol, followed by RA and XA. Competition between Ni²⁺ and Ca²⁺ was higher than that between Ni²⁺ and Na⁺ in all soil samples, as shown by the higher percentage of Ni adsorption at pH 5. At pH values below the intersection point of the three ionic strength curves (zero point of salt effect), Ni adsorption was generally higher in the more concentrated solution (highest IS), probably due to the neutralization of positive charges of soil colloids by Cl⁻ ions and consequent adsorption of Ni²⁺. Above this point, Ni adsorption was higher in the more diluted solution (lowest ionic strength), due to the higher negative potential at the colloid surfaces and the lower ionic competition for exchange sites in soil colloids. Conclusions  The effect of ionic strength was lower in the Oxisols than in the Alfisol. The main mechanism that controlled Ni adsorption in the soils was the ionic exchange, since the adsorption of ionic species varied according to the variation of pH values. The ionic competition revealed the importance of electrolyte composition and ionic strength on Ni adsorption in soils from the humid tropics. Recommendations and perspectives  The presence of NaCl or CaCl₂ in different ionic strengths affects the availability of heavy metals in contaminated soils. Therefore, the study of heavy metal dynamics in highly weathered soils must consider this behavior, especially in soils with large amounts of acric components.     

Ion adsorption mechanisms in oxidic soils; implications for point of zero charge determinations

In order to clarify the adsorption mechanisms for various ions (e.g., P, K, Ca, Mg), ion adsorption studies were carried out on a range of soils of widely different mineralogical compositions. The soils were classified as: Hydrandept, Gibbsihumox, Eutrustox and Haplustoll and belonged, respectively, to the Honokaa, Halii, Wahiawa and Waialua soil series in Hawaii.Soils containing mostly hydrous Fe and Al oxides, thus colloids of the variable-charge type, retain ions through various types of adsorption mechanisms. As a result, certain interactions between cation adsorption and anion adsorption occur which affect the ion exchange processes and thereby the determination of the point of zero charge (PZC).In this study adsorbed phosphate increased the adsorption of cations and lowered the PZC and adsorbed Ca interfered with PZC determinations unless these were carried out with CaCl₂ as supporting electrolyte. It is likely that this latter interference will have influenced the results of many earlier studies because of the very strong adsorption of Ca by oxidic colloids. In this study only part of the adsorbed Ca could be recovered from the two most highly weathered soils, by repeated extractions with NH₄-acetate at pH 7.The results indicate that many soils of the tropics can be characterized effectively by their PZC's. One should be aware, however, of the effects of strongly adsorbed ions commonly present in these soils and thus use those supporting electrolytes for the PZC determinations which counteract these effects.     

Zinc adsorption characteristics of selected calcareous soils of Iran and their relationship with soil properties

Abstract

The apparent recovery of applied zinc (Zn) by plants is very low in calcareous soils of Iran because most of it is retained by the soil solids. Subsamples of 24 surface soil (clay 130–530 g kg^‐1; pH 7.7–8.4; electrical conductivity 0.63–3.10 dS m^‐1; organic matter 6.0–22.0 g kg^‐1; cation exchange capacity 8–20 cmol kg^‐1; calcium carbonate (CaCO₃) equivalent 180–460 g kg^‐1) representing 13 soil series in three taxonomic orders were equilibrated with zinc sulphate (ZnSO₄) solutions and the amount of Zn disappeared from solution after a 24‐h shaking period was taken as that adsorbed (retained) by the soil solids. The adsorption data were fitted to Freundlich (X=AC^B) and Langmuir [X=(K‐bC)/(1+K#lbC)] adsorption isotherms. Backward stepwiseprocedure was used to obtain regression equations with isotherms coefficients as dependent and soil properties as independent variables. Freundlich A and Langmuir K were found to be highly significantly related to pH and clay and increasing as these soil properties increased. But Langmuir b was related only to clay and Freundlich B showed no significant relationship with any of the properties studied. The distribution coefficient (also called maximum buffering capacity), calculated as the product of Langmuir K and b, was also found to be highly significantly related to pH and clay. It is concluded that pH and clay content of calcareous soils are the most influential soil properties in retention of Zn.     

Effects of equilibrating salt solutions on phosphate sorption by soils

Abstract

Several equilibrating salt solutions have been used in the studies of P sorption by soils and sediments. This study was conducted to evaluate the effects of 10 salt solutions on estimation of P sorption by soils. Results obtained showed that, when the equilibrating solution was made to contain 0.01M with respect to CaCl₂, Ca(NO₃)₂, CaSO₄, MgCl₂, KCl, LiCl, Nacl, or KHCO₃, the amount of P sorbed by soil always exceeded the amount sorbed from the soil‐water system. In comparison with the amount of P sorbed from water, 0.01M NaHCO₃ reduced P sorption by soils. Use of THAM buffer (0.05M pH 7.0) to control the pH increased P sorption by some soils and decreased P sorption by others, relative to that sorbed from the soil‐water system. The results indicated that inclusion of salts in the equilibrating solution for P‐sorption studies should be avoided, especially in studies related to water quality.     

Effects of temperature on phosphate sorption isotherms and phosphate desorption

Abstract

Phosphorus sorption isotherms were constructed for two Idaho soils with widely different chemical properties. The soils were equilibrated with various amounts of Ca(H₂PO₄)₂ in 0.01 M CaCl₂ for 1, 3, 7, and 11 days at temperatures of 5°C and 20°C. The two soils which had been equilibrated previously for 11 days at 20°C with various amounts of Ca(H₂PO₄)₂ in 0.01 M CaCl₂ were desorbed at 5°C and 20°C.

The rates of sorption and desorption were decreased as the equilibration temperatures were lowered. The effect of temperature on these processes was detected during the first day of equilibration. Less P was found in the equilibrating solution at the lower temperature. The two soils varied widely in sorption and desorption properties.     

THE DETERMINATION OF DESORPTION ISOTHERMS FOR SOIL PHOSPHATE USING LOW VOLUMES OF SOLUTION AND AN ANION EXCHANGE RESIN

Phosphate desorption isotherms were determined (a) by shaking 1 g soil with 3 ml 0.01M CaCl₂ solution plus different amounts of an anion exchange resin, and (b) by diluting soil with different volumes of 0.01M CaCl₂ solution. Adsorption isotherms were determined using a soil to solution ratio of 1 g to 3 ml. In soils of intermediate P status adsorption isotherms appeared continuous with desorption by method (a), but not with desorption by method (b), which predicted lower buffer powers than did (a). Method (a) led to increases and (b) to decreases in pH. Additions of dissolved silica had no influence on P desorption by method (b).     

Sorption of phosphorus by some surface soils from Quebec in relation to their properties

Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH₂PO₄ in 0.01 M CaCl₂ for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.     

Phosphate sorption curves as a soil testing technique: A simplified approach

Abstract

Single point phosphate sorption curves effectively estimated phosphate fertilizer requirements while requiring less work than multiple point curves. Correlation coefficients of 0.961 and 0.981 were obtained when phosphate rates, estimated using single point curves, were compared with those from multiple point curves. Reducing the ionic strength of the supporting electrolyte solution by using 0.001 M CaCl₂ or water rather than 0.01 M CaCl₂ during equilibration increased dissolved inorganic phosphate 73% and 141% on the average thus improving analytical precision. The relative effects of salt concentration were sufficiently independent of pH and phosphorus concentration to suggest that a simple conversion factor can be used to convert external P requirements from one set of equilibrium conditions (salt concentration) to another.     

Effect of ph on amount of phosphorus extracted by 10 mm calcium chloride from three Rothamsted soils

Abstract

Three silty clay loams from the classical field experiments at Rothamsted Experimental Station (UK) with low phosphorus (P) status were treated with phosphate fertilizer and incubated for 15 days at field capacity with added acid [hydrochloric acid (HCl)] or base [sodium hydroxide (NaOH)] to give pH ranges measured in 1:5 suspensions of soil in 10 mM calcium chloride (CaCl₂) of 6.3–8.7 (Hoosfield A, pH 8.2), 3.8–8.2 (Hoosfield B, pH 6.3), and 2.8–7.1 (Geescroft, pH 5.3). Extractable ? was measured by the 10 mM CaCl₂ extraction procedure. For the Hoosfield ? and Geescroft soils without added phosphate fertilizer, extractable ? was decreased at both ‘low’ and ‘high’ pH values, the maximum being at about 5.4 in both soils. In the calcareous Hoosfield soil, extractable ? decreased with increasing pH over the range studied. These changes in extractable ? were magnified in soils treated with phosphate fertilizer but the maxima and trends were unaltered. The results indicate that native soil ? appears to be changed by pH in the same way as added ? to the soil. In the calcareous Hoosfield A soil, added acid did not reduce soil pH to less than 6.4 (because of its high buffer capacity) and so the pH level for maximum ? solubility was not found.     

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

Abstract

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg^?1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H₂O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H₂O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=At^B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.     

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.