首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Abstract

Soil cation exchange capacity (CEC) measurements are important criteria for soil fertility management, vaste disposal on soils, and soil taxonomy. The objective of this research was to compare CEC values for arable Ultisols from the humid region of the United States as determined by procedures varying widely in their chemical conditions during measurement. Exchangeable cation quantities determined in the course of two of the CEC procedures were also evaluated. The six procedures evaluated were: (1) summation of N NH4OAc (pH 7.0) exchangeable Ca, Mg, K, and Na plus BaCl2 ‐ TEA (pH 8.0) exchangeable acidity; (2) N Ca(OAc)2 (pH 7.0) saturation with Mg(OAc)2 (pH 7.0) displacement of Ca2+; (3) N NH4OAc (pH 7.0) saturation with NaCl displacement of NH4 +; (4) N MgCl2 saturation with N KCl displacement of Mg2+; (5) compulsive exchange of Mg2+ for Ba2+; and (6) summation of N NH4OAc (pH 7.0) exchangeable Ca, Mg, K, and Na plus N KCl exchangeable AJ. The unbuffered procedures reflect the pH dependent CEC component to a greater degree than the buffered methods. The compulsive exchange and the summation of N NH4OAc exchangeable cations plus N KCl exchangeable Al procedures gave CEC estimates of the same magnitude that reflect differences in soil pH and texture. The buffered procedures, particularly the summation of N NH4OAc exchangeable cations plus BaCl2 ‐ TEA (pH 8.0) exchangeable acidity, indicated inflated CEC values for these acid Ultisols that are seldom limed above pH 6.5. Exchangeable soil Ca and Mg levels determined from extraction with 0.1 M BaCl2 were consistently greater than values for the N NH4Oac (pH 7.0) extractions. The Ba2+ ion is apparently a more efficient displacing agent than the NH4 + ion. Also, the potential for dissolving unreacted limestone is greater for the Ba2 + procedures than in the NH4 + extraction.  相似文献   

2.

Background

Cation exchange capacity (CEC) is a routinely measured soil fertility indicator. The standard NH4OAc (pH 7) extraction procedure is time-consuming and overestimates actual CEC values of variable charge soils. Unbuffered extractants have been developed to measure the effective CEC (eCEC), but they differ in the type of index cation and extraction procedures.

Aim

This study was set up to systematically compare CEC values and exchangeable cation concentrations among different procedures and evaluate their practical aspects.

Methods

Five procedures were compared for (e)CEC, that is, silver thiourea (AgTU), cobalt(III) hexamine (Cohex), compulsive exchange (CE, i.e., BaCl2/MgSO4), BaCl2 (sum of cations in single-extract), and NH4OAc (pH 7). We applied these methods to a set of 25 samples of clay minerals, peat, or samples from soils with contrasting properties.

Results

The CEC values correlated well among methods (R2 = 0.92–0.98). Median ratios of eCEC (AgTU as well as CE) to the corresponding eCEC (Cohex) value were 1.0, showing good agreement between eCEC methods, but NH4OAc exceeded Cohex values (ratios up to 2.5 in acid soil). For BaCl2-extracteable cations, the ratio ranged from low (<1.0) in acid soils (acid cations not measured) to high (>1.0) in high-pH soil (dissolution of carbonates). Multiple-extraction methods (CE and NH4OAc) yielded more variation and increased labor.

Conclusions

The chemical properties of the sample cause method-specific interactions with chemical components of extractants. We found the Cohex method with ICP-MS detection to be the most efficient and cost-effective technique for determination of eCEC and exchangeable cations.  相似文献   

3.
Abstract

Eight methods to determine exchangeable cations and cation exchange capacity (CEC) were compared for some highly weathered benchmark soils of Alabama. The methods were: (1) 1N NH4OAc at pH 7.0 by replacement (for CEC only), (2) 1N NH4OAc at pH 7.0 (summation of basic cations plus 1N KCl extractable Al), (3) 1N NH4OAc at pH 7.0 (summation of basic cations plus exchangeable H+), (4) 0.1M BaCl2 (summation of basic cations plus exchangeable Mn, Fe and Al), (5) Mehlich 1 (summation of basic cations plus 1N KCl extractable Al), (6) Mehlich 1 (summation of basic cations plus exchangeable H+), (7) Mehlich 3 (summation of basic cations plus 1N KCl extractable Al), and (8) Mehlich 3 (summation of basic cations plus exchangeable H+). The 0.1M BaCl2 was chosen as the standard method for the highly weathered soils and the other methods compared to it. The results indicated that the 1N NH4OAc replacement method gave significantly higher CEC values compared to the summation methods. This was probably due to the overestimation of the field CEC caused by measurement of pH dependent cation exchange sites in these soils. There was, however, close agreement between the BaCl2 method and the summation methods that included extractable Al. The generally good agreement between these summation methods suggests that the Mehlich 1 and Mehlich 3 extractants, commonly used to determine available nutrients in the southeastem USA, may also be used to measure effective CEC of some acid‐rich sesquioxide benchmark soils of Alabama. However, 1N KCl extractable Al as opposed to exchangeable H+ should be included in the computation.  相似文献   

4.
Abstract

In soil samples from two study sites in southern Norway, exchangeable cations were determined using two different ammonium (NH4)‐salts as extractant. As expected, the cation exchange capacity (CEC) determined in 1M ammonium acetate (NH4OAc), buffered at pH 7.0 was higher than the CEC measured in ammonium nitrate (NH4NO3). By contrast, the amount of exchangeable calcium (Ca), magnesium (Mg), and barium (Ba) was lowest in the NH4OAc extract, in particular in the upper soil horizons high in organic matter (O‐ and E‐horizon). This suggests that NH4 in 1M NH4OAc does not compete effectively with multivalent base cations. The relatively high levels of exchangeable base cations in NH4NO3 could not be explained by increased weathering. An increase in selectivity of especially divalent cations may explain the relatively low amount of exchangeable base cations extracted by NH4OAc, as this involves increased deprotonation and thus a higher negative charge.  相似文献   

5.
Abstract

A study was conducted with the purpose of comparing the efficiency of Mehlich 1, Mehlich 3, and calcium acetate lactate (CAL) extractants for the deter‐ mination of available phosphorus (P) and exchangeable cations [potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na)] on 22 Ethiopian and 10 German agricultural soils. The Olsen and NH4OAc extractants were used as standards against which P and exchangeable cations values were compared. Results showed that, in general, highly significant correlations were found between all of the methods for available P and exchangeable cations determination on the Ethiopian soils. The highest correlation was, however, found with the Mehlich 3 extractant. On the ten soils from Germany, the Olsen method did not give significant cor‐ relation with the CAL method for P determination. The CAL and Mehlich 3 extrac‐ tants were also not good indicators of Na availability when compared with the NH4OAc method. It can be generalized that the Mehlich 3 is a suitable extractant for P, K, Ca, Mg, and Na in Ethiopian soils, but further study is recommended to confirm these findings under field conditions.  相似文献   

6.
Most Brazilian soil-testing laboratories use Mehlich 1 and 1.0 M potassium chloride (KCl) solutions as extractants for the determination of phosphorus (P), potassium (K), and sodium (Na) and for exchangeable calcium (Ca), magnesium (Mg), manganese (Mn), and aluminum (Al) in agricultural soil samples. Other laboratories use a combination of exchangeable ionic resin and KCl procedures. With recent adoption of the inductively coupled plasma (ICP-OES) in routine soil-testing laboratories, soil extraction with 1.0 M ammonium chloride (NH4Cl) became an alternative due to the possibility of determining all exchangeable elements in one run (Ca, Mg, K, Mn, Na, and Al), leaving determination of phosphorus (P) with Mehlich 1 or exchangeable ionic resin. To evaluate the performance of the NH4Cl solution, an experiment was carried out with thirty-seven samples of soils representative of the southernmost state of Brazil, Rio Grande do Sul. Four extraction solutions [Mehlich 1 at soil/solution ratio of 1:10 and 1.0 M ammonium acetate (NH4OAc), 1.0 M KCl, and 1.0 M NH4Cl at soil/solution ratio 1:20] were used with three different shaking times (5, 30, and 60 min). Correlation coefficients among all methods were high. Mehlich 1 did not perform well against NH4OAc and NH4Cl, despite the high correlation coefficients, with values consistently lower for K, even when the time of extraction was increased from 5 to 30 or 60 min. However, for concentrations less than 0.30 cmol kg?1 (i.e., in the range of K deficiency), both solutions performed similarly. Calcium and Mg increased with time of shaking. Comparable values of exchangeable Ca, Mg, and K, as well as of Al and Mn, were obtained with 1.0 M NH4Cl with 60 min shaking and the standard procedures of 1.0 M NH4OAc and 1.0 M KCl. The determination of Al by traditional titration/back-titration of the 1.0 M KCl solution gave slightly greater results compared to ICP-OES obtained using extraction with 1.0 M NH4Cl. The results indicate that for Ca, Mg, Mn, and Al, it is possible to replace the traditional 1.0 M KCl extraction with 1.0 M NH4Cl solution, with 60 min shaking time and a soil/solution ratio of 1:20.  相似文献   

7.
Abstract

Eighty four soil samples collected from southeastern Norway were analyzed for Cd by extraction with NH4OAc, DTPA, NH4OAc-EDTA, NH4NO3, HCl and CaCl2. The total Cd, pH, exchangeable K and Ca, dithionite-extractable Mn, available P and fine sand (0.2–0.02 mm) contents were the principal factors related to the extractable Cd, with some inter-extractant variations. Cadmium extracted by NH4NO3, NH4OAc, HCl and CaCl2 decreased with increasing soil pH, but the Cd extracted by all the extractants increased with increasing total Cd, exchangeable K and Ca, available P, and Mn-oxide contents in the soils. The Cd concentrations in plants were significantly related to the extractable Cd, exchangeable Ca and Mg, pH, Mn-oxides and organic matter content.  相似文献   

8.
Abstract

Since only one extraction is required to determine a large number of nutrients, many laboratories employ universal extractants to determine the available nutrients in a soil sample. This paper compares the universal ammonium bicarbonate‐DTPA (AB‐DTPA) method developed by Soltanpour and Schwab (1977) with the traditional methods, ammonium acetate (NH4OAc) test for exchangeable cations and the Lindsay and Norwell (1969) test for the micronutrients. Results from the analysis of 28 soils by these methods were compared. Most soils were selected from those used by the Spanish Working Group for the Standardization of Analytical Methods. In most cases, statistical correlations between methods presented good agreement for each element, but depending on the soil pH range, some elements needed two correlations. Also, when results for wet and dry soils were compared, variability was lower when the AB‐DTPA extraction method was used. We concluded that, besides being faster, the AB‐DTPA method is valid for Spanish soils, even for calcium (Ca) extraction in calcareous soils, where the ammonium acetate method fails due to excessive Ca solubilization.  相似文献   

9.
Abstract

Soil Samples (72) were collected from the Delta, Hill, and Northeast Blackland areas of Mississippi. Chemical analyses for manganese, magnesium, and calcium were made using the Mississippi Soil Test Solution (MSTS) and several other extracting solutions chosen for comparison. For the determination of available soil manganese, the MSTS proved to be as effective as either the Double Acid (0.025 N HCl in 0.05 N H2SO4) or 0.1 N H3PO4. The acid extractants removed more manganese than 1 N NH4OAc (pH 7.0) and therefore included forms that are not exchangeable. The methods studied for magnesium determinations were equilibrium extraction with 1 N NH4OAc, MSTS, Double Acid, 0.25 N CaCl2, and leaching with 1 N NH4OAc. All methods were highly correlated and therefore would be equally effective in determining available soil magnesium. Since MSTS and equilibrium extraction with 1 N NH4OAc removed similar amounts of magnesium from the soil, the same calibration can be used. Calcium determinations were made using equilibrium extraction with 1 N NH4OAc, MSTS, and Double Acid, and by leaching with 1 N NH4OAc. All methods proved effective in measuring available soil calcium on acid soils.  相似文献   

10.
The extraction of earth alkaline and alkali metals (Ca, Mg, K, Na), heavy metals (Mn, Fe, Cu, Zn, Cd, Pb) and Al by 1 M NH4NO3 and 0.5 M NH4Cl was compared for soil samples (texture: silt loam, clay loam) with a wide range of pH(CaCl2) and organic carbon (OC) from a forest area in W Germany. For each of these elements, close and highly significant correlations could be observed between the results from both methods in organic and mineral soil horizons. The contents of the base cations were almost convertible one‐to‐one. However, for all heavy metals NH4Cl extracted clearly larger amounts, which was mainly due to their tendency to form soluble chloro complexes with chloride ions from the NH4Cl solution. This tendency is very distinct in the case of Cd, Pb, and Fe, but also influences the results of Mn and Zn. In the case of Cd and Mn, and to a lower degree also in the case of Pb, Fe, and Zn, the effect of the chloro complexes shows a significant pH dependency. Especially for Cd, but also for Pb, Fe, Mn, Zn, the agreement between both methods increased, when pH(CaCl2) values and/or contents of OC were taken into account. In comparison to NH4Cl, NH4NO3 proved to be chemically less reactive and, thus, more suitable for the extraction of comparable fractions of mobile heavy metals. Since both methods lead to similar and closely correlated results with regard to base cations and Al, the use of NH4NO3 is also recommended for the extraction of mobile/exchangeable alkali, earth alkaline, and Al ions in soils and for the estimation of their contribution to the effective cation‐exchange capacity (CEC). Consequently, we suggest to determine the mobile/exchangeable fraction of all elements using the NH4NO3 method. However, the applicability of the NH4NO3 method to other soils still needs to be investigated.  相似文献   

11.
Abstract

The ammonium acetate (NH4OAc)‐EDTA soil phosphorus (P) extraction method was compared to either the Bray‐1 soil P extraction method for non‐calcareous soils or the Olsen soil P extraction method for calcareous soils to predict com and wheat plant tissue P concentration and grain yield responses. The NH4OAc‐EDTA method predicted yield and tissue P concentration responses to P fertilizer applications more accurately than the Olsen method at three of five sites. Both the Bray‐1 and NH4OAc‐EDTA methods were successful in predicting corn and wheat yield responses to P fertilizer applications in non‐ calcareous soils in many locations. However, a direct comparison of extracted soil P levels showed that the NH4OAc‐EDTA method extracted soil P at levels which were more closely related to the Bray‐1 method than the Olsen method.  相似文献   

12.
Soils from the C-horizon of deciduous forests in southern Sweden, originally sampled in 1947-52, were resampled in 1988. Air-dried soil from both periods were extracted in 1991 using M NH4Ac, pH 4.8, and 0.2 M HNO3 for analysis of exchangeable and acid soluble pools of Na, Mn, Ca, Mg, K, Sr, Zn, Fe, S, P, and Al. Using acid NH4Ac as extractant nine elements had changed significantly (p<0.05) over 40 yr. In particular, the pools of exchangeable base cations and Mn had decreased, whereas those of Al, S, and Fe had increased. The HNO3 extraction showed the same tendency as NH4Ac for most elements, but the relative changes were always smaller. The largest decrease was measured in Na with both extractants (only 10 to 30% remaining in 1988). Of K, Mg, Ca, and Sr, about 40 to 60% remained with NH4Ac and about 70% with HNO3. The NH4Ac exchangeable pool of Al, on the contrary, was twice as high in 1988 as in 1947–52. Amounts obtained with the two extractants were usually positively correlated (r>0.90 for Na, K, Mg, and Sr), but with the exception of S, values for HNO3 were higher or much higher. It is concluded that a decided decrease of the exchangeable pools of base cations and an equally decided increase of exchangeable Al has occurred even in the C-horizon, well below the main rhizosphere. That also the acid soluble pools of base cations have decreased indicates mineralogical changes which may counteract a complete reversibility of the current soil acidification.  相似文献   

13.
A Method for the Determination of Exchangeable Cations in Forest Soils A simple extraction method with NH4Cl was developed for determining exchangeable cations in forest soils. The influence of selected parameters (reaction time, concentration of NH4Cl, filter medium etc.) affecting the amount of extractable cations was tested and a standardisation was done. The cation exchange was completed in less than 4 h. For a quantitative extraction of K, Mg, Ca, and Mn a concentration of 0.05 M NH4Cl was sufficient. The extractable amount of these cations was always clearly defined. However, extracted Al and Fe increased with the NH4Cl-concentration. Depending on the soil samples, the exchange is not quantitative even when using a saturated solution. The extractable H+ is nearly independent of the NH4Cl-concentration. Probably considerable amounts are dissociated from organic acids. The optimized method is feasible and can be used for K, Mg, Ca, and Mn as an alternative to percolation methods.  相似文献   

14.
Abstract

In this study, a new parallel and sequential extraction procedure was proposed to investigate the solubility of metals [cadmium (Cd), zinc (Zn), copper (Cu), and nickel (Ni)] and their association with soil components in naturally metal‐rich soils of Norway. Two different soils, alum shale (clay loam) and moraine (loam), developed on alum shale minerals were used. Each soil had two pH levels. For parallel and successive extractions, H2O, 0.1M NH4OAc (soil pH), 0.3M NH4OAc (soil pH), 1M NH4OAc (soil pH), and 1M NH4OAc (pH 5.0) were used. A significant amount of Cd was extracted by NH4O Ac related to concentration of NH4OAc in the extracting solution. The amounts of Zn, Cu, and Ni extracted by these reagents were almost negligible except with 1M NH4OAc (pH 5.0). Thus these metals were strongly bound to soil components. A seven step sequential extraction procedure was applied to evaluate the association of metals with soil constituents. The extractions were performed sequentially by extracting the soil with reagents having an increasing dissolution strength: 1M NH4OAc (soil pH), 1M NH4OAc (pH 5.0), 1M NH2OH.HCl (in 25% HOAc), 1M NH2OH.HCl (in 0.1M HNO3), 30% H2O2 (in 0.1M HNO3), 30% H2O2 (1M HNO3), and aqua regia. In both soils at both pH levels investigated, appreciable percentages of total Cd (20–50%) were found associated with the NH4OAc extractable fraction (mobile fraction). For Zn, Cu, and Ni, the percentage of total metal extracted with NH4OAc was low (<4%), but it increased significantly by introducing a reducing agent (NH2OH.HCl). The NH2OH.HCl‐extractable fraction was the greatest fraction (>60%) for all four metals examined. These results suggest that among the metals studied, only Cd was easily desorbed from soil and should be considered mobile and potentially bioavailable. Other metals (Zn, Cu, and Ni) were strongly associated with the soil components and should be considered less available to plants. Using the sequential fractionation technique as a measure of availability, mobility and potential bioavailability of these four metals in the alum shale soils were: Cd>Zn>Ni>Cu.  相似文献   

15.
We determined proton budgets of surface soils in a deciduous forest (Df) and a coniferous forest (Cf) of Volcanogenous Regosols in Tomakomai, Hokkaido of northern Japan. The total H+ source was 12.9 and 11.6 kmolc ha?1 y?1 at Df and Cf respectively, and the external H+ was 1% at Df and 2% at Cf. The primary H+ sources were vegetation uptake of base cations and nitrification, while the major H+ sinks were release of base cations and NO3 + uptake by vegetation. Leaching incubation experiments using A horizon soils including Df and Cf with NH4 + solutions (5.3, 15.9 mg N L?1) showed that H+ from nitrification was generally higher in the Df soil than Cf soil, and nitrification of Tomakomai Df soil was the highest in both treatments. Results of multiple regression analyses suggested that pHkCl and exchangeable Ca2+ contributed to the H+ generation via nitrification. Leaching experiments with dilute HCl (pH 3.3) revealed that cation release (mainly Ca2+) occurred, and the proportion of release by decrease of exchangeable cations was higher than that by mineral weathering. Mineral weathering in the Tomakomai soil was higher than the other soils.  相似文献   

16.
Human exposure to toxic heavy metals via dietary intake is of increasing concern. Heavy-metal pollution of a rice production system can pose a threat to human health. Thus, it was necessary to develop a suitable extraction procedure that would represent the content of metal available to rice plants (Oryza sativa L.). The aim of this study was to predict, on the basis of single extraction procedures of soil heavy metals, the accumulation of heavy metals (cadium, lead, copper, and zinc) in rice plants. Six extracting agents [Mehlich 1, Mehlich 3, EDTA (ethylenediaminetetraacetic acid), DTPA–TEA (diethylenetriaminepentaacetic acid–triethanolamine), ammonium acetate (NH4OAc), and calcium chloride (CaCl2)] were tested to evaluate the bioavailability of heavy metals from paddy soils contaminated with lead–zinc mine tailings to rice. The extraction capacity of the metals was found to be of the order EDTA > Mehlich 3 > Mehlich 1 > DTPA–TEA > NH4OAc > CaCl2. The correlation analysis between metals extracted with different extractants and concentrations of the metals in the grain and stalk of the plant showed positive correlations with all metals. The greatest values of correlation coefficients were determined between the NH4OAc- and CaCl2-soluble fractions of soil and contents in plants in all four metals studied. Therefore, NH4OAc and CaCl2 were the most suitable extractants for predicting bioavailability of heavy metals in the polluted soils to rice. The results suggested that uptake of heavy metals by rice was mostly from exchangeable and water-soluble fractions of the metals in the soils. Soil-extractable metals were more significantly correlated with metal accumulation in the stalk than in the grain. The pH had more significant influence on availability of heavy metals in the soils than total content of metals and other soil properties. The bioavailability of metals for rice plants would be high in acidic soils.  相似文献   

17.
Cation exchange is often studied with disturbed and dried soils, but the applicability of the results to undisturbed soils is not straightforward. We investigated the value of exchange coefficients obtained from standard procedures for predicting cation exchange in soil. Columns of undisturbed and disturbed subsoil of a Luvisol (SBt horizon) were leached under saturated conditions with 0.4, 4, 20, 41, 102 and 205 mm BaCl2 at a Darcy velocity of 1400 mm day?1. The model PHREEQC was used to calculate one‐dimensional transport, inorganic complexation and multiple cation exchange. Two model variants were tested: m1 (exchangeable cations obtained by percolation with NH4Cl) and m2 (exchangeable cations obtained by shaking the soil with BaCl2). The exchange coefficients (Gaines–Thomas formalism) were calculated from the ion activities in solution and exchangeable cations obtained by NH4Cl percolation (m1) or shaking with BaCl2 (m2). Variant m1 predicted cation exchange of the disturbed (homogenized) soil for the entire BaCl2 concentration range, whereas variant m2 resulted in a two‐fold overestimation of desorbed K for all experiments, which was related to large amounts of K released from the soil by shaking with BaCl2. In experiments with undisturbed soil, variant m1 predicted the concentrations of Mg, Ca, K, and Na in the solution phase and the sum of cations released from exchange sites. However, variant m2 predicted changes in ion concentrations and exchangeable cations somewhat less well. This study suggests that the amounts of exchangeable cations and exchange coefficients obtained from experiments with homogenized soil by percolation are useful to predict cation concentrations in column experiments with undisturbed soils.  相似文献   

18.
Comparison between percolation and extraction with 1 M NH4Cl solution to determine the effective cation exchange capacity (CECeff) of soils A simple method is proposed for the determination of the effective cation exchange capacity (CECeff). The soil is extracted with 1 M NH4Cl‐solution, manually shaken for three times, and the exchangeable cations are determined by ICP‐OES and pH‐measurement. Comparison with corresponding results of the percolation method (n = 110 samples) shows good agreement in reproducibility, exchangeable cations (except Fe and Na), base saturation and CECeff.  相似文献   

19.
Accurate soil testing procedures contribute to agricultural development of Mozambique. The Mehlich 3 (M-3) procedure has not been evaluated for Mozambican soils despite its wide applicability. Results showed M-3 solution could extract exchangeable calcium (Ca), magnesium (Mg), and potassium (K) as well as 1 M ammonium acetate (NH4OAc), while M-3 was not appropriate for extraction of exchangeable sodium (Na). M-3 was an alternative procedure to Bray-I for available phosphorus (P) extraction. Although M-3 extracted 1.6 times more P than Bray-I, determination coefficient between the two procedures showed significantly high value. P content in M-3 extracts can determine using inductively coupled plasma spectrophotometers (ICP) to maximize the merits of M-3. In conclusion, M-3 is applicable for determination of exchangeable Ca, Mg, K, and available P, in a single determination using ICP, and should contribute to development of effective and accurate soil diagnosis in Mozambique.  相似文献   

20.
The anion exchangeable membrane phosphorus (P) method can be used across a range of soils to analyze P for vegetation and has the potential to be applied to heterogeneous mine soils. Enhanced small-scale variability in mine soils can potentially cause enhanced and irregular P fluctuations during extraction, leading to errors in analysis of exchangeable membrane P. Anion exchange membranes in combination with low ionic solutions may be able to reduce this error and improve precision of the measurement. The authors undertake a full inorganic P fractionation to determine if the ionic solutions [deoionized water (DI), 0.01 M calcium chloride (CaCl2), potassium chloride (KCl), and ammonium fluoride (NH4F)] change the anion exchangeable membrane–extractable P and in turn the fractionation of P. In addition, the relationship between anion exchangeable membrane P and P-buffering index is analyzed to ascertain the accuracy of the methods. The precision and effect on subsequent P fractions for each extracting reagent was specific to the soil type, most likely related to cations in the soil. Use of NH4F and DI with anion exchange membranes was a precise method [coefficient of variation (CV) < 20%] for measuring water exchangeable P, with no or minor changes to subsequent fractionations. Calcium chloride (CaCl2) causes significant changes to P fractionations and resulted in highly variable (CV > 100%) results across all soils.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号