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1.
The deposition of magnesium (Mg)‐rich dust from magnesite mining activities has resulted in serious land degradation. However, the main factors limiting plant growth in Mg‐contaminated soils are unclear. Moreover, little information is available on the remediation of Mg‐contaminated soils. In this study, remediation of soils contaminated with Mg‐rich dust was investigated in a pot experiment using maize as the indicator plant. There were five treatments: (i) control; (ii) leaching; (iii) application of CaCl2; (iv) leaching + CaCl2 application; and (v) application of Ca(H2PO4)2 · H2O. Soil properties and growth of maize (Zea mays L.) seedlings were measured. Leaching alone significantly decreased soluble Mg concentration. Leaching + CaCl2 application greatly increased exchangeable Ca concentration and decreased soil pH by 0·3 units. Application of CaCl2 alone increased soluble Mg concentration sharply, which directly inhibited the germination of maize seeds. Application of Ca(H2PO4)2 · H2O significantly increased the concentrations of exchangeable Ca and available phosphorus and decreased soil pH by 1·7 units. The biomass of maize seedlings increased in the order of control = leaching < leaching + CaCl2 < < Ca(H2PO4)2 · H2O. These results suggested that the plant growth in Mg‐contaminated soils was limited primarily by Ca deficiency and secondarily by high soil pH when exchangeable Ca was sufficient. High soil pH suppressed plant growth probably mainly by inhibiting phosphate uptake from the soil. Applying acid Ca salt with low solubility is an attractive option for the remediation of Mg‐contaminated soils. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2.
Abstract

It was the objective of this study to compare the suitability of different extractants for predicting the availability of sulfur (S) in natural grassland in a sulfur response trial on three different soil types in the Inner Mongolia steppe of China. For soil analysis, seven different extractants have been employed. The inorganic SO4–S concentration was determined by ion chromatography. Additionally, in the Ca(H2PO4)2 extract the total soluble S was determined employing turbidimetry. Weak salt solutions (0.15% CaCl2, Ca(H2PO4)2, and KH2PO4) extracted similar amounts of SO4–S. Extraction with 0.025 M KCl provided the lowest SO4–S values. Deionized water dissolved significantly more SO4–S in the control plots than most weak salt extractants. The concentration of soluble organic S decreased in the control plots after 100 days of plant growth, indicating that the organic S pool contributed significantly to the S nutrition of the forage crops. Significant relationships among the SO4–S in the soil determined in different extracts and crop yield, sulfur content in the forage, and total sulfur uptake were only found for the Ca(H2PO4)2 extract. In general, the correlation coefficients proved to be unsatisfactory for field experimentation.  相似文献   

3.
Abstract

To evaluate conventional calcium dihydrogen phospahte [Ca(H2PO4)2] solution containing 500 mg P/L as an extractant for soluble plus adsorbed sulfate (SO4), we added known amounts of SO4 to 10 soil samples differed in clay mineral composition and extracted with Ca(H2PO4)2 solution. The experimental results showed that the five successive extractions at a soihsolution ratio of 1:10 could quantitatively recover the added SO4, and there was little effect of air‐drying the soils after addition of SO4. Based upon these experimental results, we concluded that the Ca(H2PO4)2 extraction is an excellent method for determining soluble plus adsorbed inorganic SO4 in soils.  相似文献   

4.
Abstract

A modified selenium (Se) fractionation procedure was used to study Se distribution in three soils (two silt loams and one silty clay). This sequential procedure consisted of: i) 0.2 M potassium sulfate (K2SO4)‐soluble fraction, ii) 0.1 M potassium dihydrogen phosphate (KH2PO4)‐exchangeable fraction, iii) 0.5 M ammonium hydroxide (NH3H2O)‐soluble fraction, iv) 6 M hydrochloric acid (HCl)‐extractable fraction, and v) residual fraction digested with perchloric (HClO4) and sulfuric (H2SO4) acids. The fractionation procedure had high recovery rates (92.5 to 106%). The Se distribution in soil was controlled by soil properties, such as pH, oxide, clay, and calcium carbonate (CaCO3) contents. In the untreated soil samples, residual Se fraction was dominant. In the Se‐enriched soils, the silty clay had significantly more Se in the NH3H2O and residual fractions while in the two silt loams the largest were KH2PO4 and residual fractions. The Se availability in the two silt loams was higher than in the silty clay. The Se availability pattern in the untreated soils was: unavailable (HCl + residual fractions) >> potentially available (KH2PO4 + NH3H2O fractions) > available (K2SO4 fraction), while in the Se‐enriched soils it was potentially available > unavailable > available.  相似文献   

5.
Abstract

Two soil tests commonly used to characterize the availability of soil phosphorus (P) are Bray P1 (B1) and Mehlich 3 (M3) extradants. The objective of this investigation was to compare M3‐ and B1‐extractable P levels in a Starr clay loam (fine‐loamy mixed thermic Fluventic Dystrochrepts) amended with relatively low to high surface applications of poultry litter (PL). The following eight treatments were applied to the soil for pasture renovation in 1991 and 1992: 1) a control, 2) P application as monocalcium phosphate [Ca(H2PO4)2‐H2O], 3) P application as Ca(H2PO4)2‐H2O and nitrogen (N) application as ammonium nitrate (NH4NO3) and urea, and 4) five levels of poultry litter (PL) based on N content. The five P levels as PL were 56.6, 113.2, 169.8, 226.4, and 283.0 kg ha‐1 in 1991, and 49.2, 98.5, 147.7, 196.9, and 246.1 kg ha‐1 in 1992, respectively. Soil samples were obtained from the 0‐ to 5‐cm layer in the spring of 1992 and 1993 for extractable P determination. Levels of P extracted from all treatments by the M3 and B1 extractants were linearly correlated both years (r2=0.96 in 1991 and r2=0.99 in 1992). However, M3 extracted more P from the PL treatments, whereas B1 extracted more P from the control, P application, and N and P application treatments. Curvilinear relationships were obtained between P uptake and levels of either M3‐ or B1‐extractable P for the PL treatments (r2=0.713 for M3 and 0.663 for B1 in 1991 and r2=0.925 for M3 and 0.933 for B1 in 1992). These close relationships in 1992 between extractable P and uptake of P for the PL‐ treated soils indicate that both the B1 and M3 extractants could be used to evaluate excess P in PL‐amended soils.  相似文献   

6.
Abstract

An experiment was carried under controlled conditions to investigate the influence of the anions, H2PO4 ‐. and Cl on the ionic equilibria, selectivity and effective diffusion of Rb, K, Na, Ca, Mg in two Indiana soils.

Additon of anions to the soils increased the concentration of cations in soil solution. In both the soils receiving H2PO4 ‐, lower cation concentrations were found in the soil solution than in those receiving Cl‐ . Additon of H2PO4 ‐and Cl‐ reduced the ion selectivity coefficient, k, for various homovalent (Rb/K, Rb/Na, K/Na, Ca/Mg) and mono‐divalent ion pairs (Rb/Ca, Rb/Mg, K/Ca, K/Mg). In Zanesville soil treatments receiving H2PO4 ‐ had lower k values for mono‐divalent cations than treatments receiving Cl‐. However, no such conclusions could be drawn for Raub soil. Soils treated with H2PO4 ‐ had higher k values for homovalent cations than Cl‐ treated soils. The differences in the selectivity of adsorption in these two soils might be attributable to the differences in the type and nature of exchange materials and cation concentrations on the exchange phase.

Addition of H2PO4 ‐ or Cl‐ enhanced the magnitude of effective diffusion coefficient. (De) of all the cations under considerations. The magnitude of effective diffusion coefficient for cations was lower for H2PO4 ‐ treated soils than Cl‐ treated soils. Such a reduction in De is related to the reduction in cation concentration in soil solution thereby increasing the buffer capacity for the ions under consideration.  相似文献   

7.
Abstract

Soils have substantial capacity for sorption of sulfur dioxide (SO2) but little is known about the nature of the sorbed S. Three surface soils varying in pH, organic matter, CaCO3 equivalent and surface area were exposed to air containing 5% SO2 and subsequently analyzed by ten different procedures to characterize the sorbed S. Most of the sulfur retained by soils after exposure to SO2 could be recovered as CaCl2‐extractable S, Ca(H2PO4)2‐extractable S, or S released as H2S by hydriodic acid (HI). Only small amounts of sulfur could be recovered as tetrachloromercurate (TCM)‐extractable S, S released as SO2 by HCl, or S released as H2S by HCl + Zn, HCl + Sn, or Raney Ni and NaOH. However, large amounts of S released as SO2 by HCl were recovered from the air‐dry Webster and the moist Storden soils indicating that SO2 sorption is influenced by organic matter in air‐dry soils and by CaCO3 in moist soils.  相似文献   

8.
Soil sulfur (S) analyses for fertilizer recommendations in the northern Great Plains often do not reflect crop S requirements. Seven SO4-S extraction methods with S determination by either turbidometry or inductively coupled plasma emission spectroscopy including Ca(H2PO4)2 and KH2PO4 (both containing 500 ug/l P), 0.25 M KCl (40 ºC) and 0.25 M KCl (room temperature), H2O, DTPA, and Mehlich 3 extractants. Three horizon depths of three soils from a previous field study were used for these comparisons. Average standard deviations for turbidometric determinations were 4.3 times greater than ICP determinations. With turbidometry, S values were H2O > KH2PO4 > Ca(H2PO4)2 > KCl (40 ºC) = KCl, while with ICP, the values were Mehlich 3 > KCl (40 ºC) = KCl > DTPA (diethylenetriaminepentaacetic acid) > KH2PO4 > H2O > Ca(H2PO4)2. Extraction with KCl at room temperature with ICP determination appears to show promise, but further method evaluation is necessary before it can be recommended as a SO4-S test method.  相似文献   

9.
Abstract

The sulphur status of 98 soils was assessed using nine methods, some of which were designed to include mineralizable sulphur. A close correlation was found between various direct extraction methods all using phosphate, though the turbidimetric method of analysis appeared to overestimate soil S values. Extractions following short term incubation with cysteine correlated significantly with direct extraction methods indicating that the soil sulphate pool is directly related to the soil's ability to mineralize readily available organic S. In contrast, incubation with elemental S gave no correlation. A respirometric method following amendment with cellulose gave only a poor correlation with two other methods. A Neubauer plant bioassay was most closely correlated to Ca (H2PO4)2‐extractable S, CaCl2‐extractable S and to extractable S following incubation with cysteine. The value of the various methods for routine use is discussed.  相似文献   

10.
Abstract

The influence of pH upon the availability of sulfate‐sulfur in sphagnum peat moss was studied. Samples of sphagnum peat moss amended with 0, 1.41, 2.82, 3.81 and 5.64 g/L Ca(OH)2, had pH values of 2.8, 3.7, 4.7, 5.8 and 7.0, respectively. Sulfate was extracted from peat samples with a 0.15% CaCl2.H2O or a 500 mg P/L (as Ca(H2PO4)2.H2O) extractant and quantified with a Dionex QIC ion Chromatograph. Sulfate availability from the CaCl2‐extracted solutions was greatest at pH 4.7 and 5.8, but highest at pH 4.7 only for the P‐extracted solutions, in which no measurable extracted sulfur was found at pH levels greater than 4.7.  相似文献   

11.
Abstract

The general concept that low‐water‐soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)‐P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)–potassium (K)–P compounds present in superphosphates [Fe3KH8(PO4)6 · 6H2O, H8, and Fe3KH14(PO4)8 · 4H2O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg?1 as neutral ammonium citrate (NAC)+H2O‐soluble P. Reagent‐grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg?1 included. Also, mixtures of both Fe‐K‐P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg?1) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water‐soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low‐water‐soluble P source cannot be deemed as ineffective at high soil pH.  相似文献   

12.
Abstract

Fertilizer recommendations need to be based on reliable soil sulfate determinations. Airdrying samples changes irreversibly many properties of soils with variable charge and might affect the extractable sulfate. In this study, sulfate extracted from air‐dry and field‐moist samples was compared. Two extracting solutions [water and 00.1 M Ca(H2PO4) 2] and two quantification methods (turbidimetry and ion chromatography) were assayed on A and B horizon samples of five Humic Acrisols from southeast Mexico. Air drying increased water‐extractable sulfate in Ah horizons, whereas in Bt horizons, it increased the 00.1 M Ca(H2PO4)2‐extractable sulfate. Airdrying increased dissolved organic carbon contents in all samples and increased soil acidity and oxalate extractable iron in 70 and 60% of the samples, respectively. Results showed larger coefficients of variation in air‐dried samples. Turbidimetry resulted less sensible than ion chromatography. To enhance sensitivity and reproducibility, particularly organic soil samples should be analyzed field‐moist and by ion chromatography.  相似文献   

13.
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.  相似文献   

14.
Four frequently used extractants (H2O, 0.1 M NaCl, 0.016 M KH2PO4, and 0.5 M NaHCO3) as well as different extraction conditions have been tested for sulphate extraction from gypsum‐free agricultural soils. Water is the preferable extractant for soils with pH > 6. Two extraction steps have to be carried out for complete extraction (> 95%). A 0.016 M KH2PO4 solution was found to be the most efficient extractant for soils with a pH < 6 within a single extraction step. A shaking frequency of 170 min‐1 and a duration of extraction of 4 hours are the optimized conditions for the sulphate extraction with H2O and KH2PO4 solution.  相似文献   

15.
Abstract

Mustard (Brassica juncea) is an important oilseed crop of northern India, which is widely grown in Delhi and adjoining States. This crop has a relatively high requirement of sulphur (S), and is sensitive to S‐deficiency. For predicting response of mustard to S application, several extractants have been tried with variable results. Since selection of a promising extractant for a particular soil needs careful consideration, the present investigation was planned to select the most promising extractant to predict the availability of S to mustard grown on Inceptisols of Delhi. For this purpose, a greenhouse experiment was conducted with twenty soils (two from each often important soil series from the cultivated alluvial soil belt of Delhi. Nine extractants, commonly used for estimating the availability of S, were evaluated and S in soil extract and in plant digest was estimated using the turbiditimetric method. The results indicate that the phosphate salt methods extracted comparatively more S than other extractants. The amount of S extracted by these extractants was found in the following order: KH2PO4‐500 ppm P>Ca(H2PO4)2‐500 ppm P>0.001 M HCl>NaOAc+HOAc>heat soluble S>0.15% CaCl2>l% NaCl> water soluble S>NH4OAc+HOAc. Simple correlation coefficients of the amounts of S extracted by different extractants and the forms of S with the plant parameters were worked out. To determine the combined effect of soil characteristics on S extraction by different extractants, stepwise multiple regression analysis was carried out. Based on this study, the suitability of the extractants for mustard crops in Inceptisols of Delhi may be arranged as follows: 0.15% CaCl2>water soluble S>0.001 M HCl>Ca(H2PO4)2‐500 ppm>1%NaCl>NH4OAc+HOAc>NaOAc+HOAc>KH2PO4‐500 ppm P>heat soluble S.  相似文献   

16.
Abstract

This paper describes a method for quantifying oxalate in soil HC1 extracts using reversed‐phase ion‐pairing high performance liquid chromatography with UV detection at 220 nm. The method was adapted from a procedure for determining urinary oxalate (6). The mobile phase was 10 percent KH2PO4 and 5 mM TBA adjusted to pH 2.0 with H3PO4. The analytical column was a totally porous, reversed‐phase silica based C‐8 column (Hibar Li‐Chrosorb?). An important step in this method was the pre‐ treatment of each soil extract with a reversed‐phase C‐18 column (SPICE? C‐18). Sample pre‐treatment removed complex, non‐polar and low polarity compounds often present in soil extracts.

The method was applied to calcareous, agricultural and organic soils materials. An oxalate accumulating fungus, Endothia Parasitica, was used as a verification of method applicability to plant‐fungal materials. Oxalate extraction was accomplished by placing 1:2 suspensions (soil: 0.1 M HCl) on a reciprocal shaker for two hours and subsequently collecting the solution by filtering through a Whatman No. 42 filter paper.

Coefficients of variation for replicate oxalate determinations were less than 10 percent. Recovery of oxalate from spiked extracts of soil and plant material were consistently between 82 and 104 percent. Detection limits were approximately 1 μM which was greater than the concentration of oxalate in saturation paste extracts. Oxalate was detected in some of these samples but could not be quantified.  相似文献   

17.
Abstract

Two methods of measuring phosphate (P) adsorption were assessed as a means of predicting soil and plant responses to P fertigation for four British Columbia (B.C.) orchard soils. In Method 1, soils at 0.1 bar moisture tension were incubated for 1, 7, 14, 28, 56, or 84 days with solutions of H3PO4 supplied as a single or eight weekly doses. In Method 2, soils were equilibrated with P solutions at 1:10 soil:solution ratio for one day. Langmuir adsorption maxima calculated from the latter data ranged from 99 to 372 mg/kg. Solution P concentrations after one day for single dose incubations and 1:10 soil:solution equilibrations were highly correlated. Solution P concentrations remained elevated for 12 weeks after both single and weekly doses in incubated soils. Four availability indices were derived from the adsorption studies:solution P after one day equilibration for both methods and the fraction of the P adsorbing surface covered by added P at either one or fifty‐six days.

Peach seedlings (Prunus persica L. Batsch) were grown for 12 weeks in the greenhouse in a randomised complete block experiment with five levels of P (0, 15.5, 31, 62, and 124 mg P/kg) supplied as H3PO4 on the same schedule as for the incubated soils. Top dry matter increased in response to the first level of added P for three soils but was not correlated with any of four P availability indices measured. Initial soil solution P concentration was a better indicator of response to P fertilizer than Kelowna‐extractable (0.25 M HCl + 0.015 M NH4F) P. Estimated critical values of soil solution P for the two adsorption methods were 0.85 μg/mL (Method 1) and 0.42 μg/mL (Method 2).  相似文献   

18.
Abstract

The availability of soil Mn to corn in relation to extractability of soil Mn by EDTA, Mg(NO3)2, CH3COONH4, hydroquinone, H3PO4, and NH4H2PO4 as affected by liming was evaluated under field conditions on a single soil type. EDTA, Mg(NO3)2 and CH3COONH4‐extractable Mn were related inversely to available Mn. No useful relationships were found between hydroquinone, H3PO4, and NH4H2PO4‐extractable soil Mn and Mn uptake by sweet corn.  相似文献   

19.
Abstract

Several phosphate solubility and availability parameters were obtained for calcareous soil samples fertilized with superphosphate, partially acidulated phosphate rock and a mixture of the two. Plant response to the fertilizer application was studied in a greenhouse experiment. The ionic product of calcium carbonate phosphate [Ca3(HCO3)3PO4] correlated best with the plant response parameters. The correlations of the plant response parameters with the other solubility parameters (CaPO4, H2PO4 or HPO4 potentials) were higher than that obtained with conventionally determined available soil phosphorus (P).  相似文献   

20.
Abstract

In recent years, ion exchange membranes (IEM) have been used successfully to determine the availability of soil nutrient elements for plants. In general, the procedures proposed are applied to the determination of a single ion, and in only a few of these studies, the selectivity of these IEM was considered. Therefore, this work was conducted (a) to find the most suitable extraction conditions for phosphate (H2PO4 ‐), nitrate (NO3 ‐), and sulfate (SO4 2‐) in soils by IEM and their subsequent determination by ion chromatography, (b) to test the effectiveness and selectivity of IEM, (c) to compare the results obtained by IEM with the common procedure for determining the availability of the soil nutrient elements, and (d) to verify whether a relation exits between the concentration of phosphorus (P) extracted by IEM and the plant P requirement. The soil samples used for this study were Humic Cambisols located in four forest plots under natural conditions and four plots fertilized with 100 kg P ha‐1 as triple superphosphate. The efficacy of the IEM was high (85% for SO4 2‐, and 92% for H2PO4 ‐ and NO3 ‐). Statistically significant correlations were obtained between the H2PO4 ‐ extracted by IEM and the H2PO4 ‐ obtained by the Bray P1 procedure (r2=0.936) and with the H2PO4 ‐ extracted using Saunders and Williams (1955) procedure (r2=0.370). The correlation obtained between the amount of NO3 ‐ extracted with IEM and that obtained using 2M potassium chloride (KCl) was also highly significant (r2=0.828). The IEM extraction allowed to know in a single extraction process and a single subsequent measurement by ion chromatography the concentrations of soil available H2PO4 ‐, NO3 ‐, and SO4 2‐ ions, which are of great plant nutrition interest. Phosphorus extractable with IEM yielded a close relationship with biomass production and could be used for determining the P requirement of these forest trees.  相似文献   

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