Comparison of Various Chemical Extraction Methods used for Determination of the Available Iron Amounts of Calcareous Soils

This study was conducted to compare the most appropriate method for the evaluation of available iron (Fe) status of calcareous soils by using nine different chemical extraction methods. Leaf and soil samples were collected from nine peach (Prunus persica L.) orchards, each of which included green, slightly chlorotic, and severely chlorotic peach trees. According to the chlorosis degrees of the leaves, total and active Fe contents and some soil properties were determined. Relationships between these parameters and Fe amounts obtained from the methods were correlated. Among the methods tested, method 3 (M3) [0.05 N hydrochloric acid (HCl) + 0.025 N sulfuric acid (H₂SO₄)] and method 8 (M8) 0.05 M ethylenediaminetetraacetic acid (EDTA) (pH 7.0) were the most suitable methods to indicate the available Fe status of the soils.     

Evaluation of Some Chelates in Estimating Available Zn for Soybean in Calcareous Soils

Six fertilizer trials on calcareous soils in Saudi Arabia were conducted for the prediction of Zn deficiency in soybean (Glycine max L., var Merr). Zinc level before planting was tested by using 3 different extractants, i.e. DTPA, AB-DTPA and EDTA. Zinc was applied in the form of ZnSO₄ · 7H₂O at 0, 5, 10, 15, 20 and 40 kg Zn ha^?1. Plant samples were taken at early bloom and tissue was analysed for Zn. Two methods were used to judge the critical deficiency level of Zn: Cate-Nelson and chisquare models. The critical level estimated according to the Cate-Nelson method for DTPA extractable soil Zn was 0.43 mg kg^?1 in the growing season 1991. EDTA gave a much higher level (1.80 mg kg^?1) and AB-DTPA gave an intermediate level (0.68 mg kg^?1). Chi-square statistical procedure gave a very similar critical level of 0.66 mg kg^?1 for AB-DTPA but lower for either DTPA (0.38 mg kg^?1) or EDTA (1.32 mg kg^?1). The critical level based for three growing seasons ranged from 0.25 to 0.68, 0.32 to 0.82 and 1.12 to 3.4 mg Zn kg^?1 for DTPA, AB-DTPA and EDTA extractants, respectively. The values obtained by the linear regression equation with soybean leaf concentration were 0.45 and 0.70 mg Zn kg^?1 for DTPA and AB-DTPA, respectively. Such values are very close to those determined by using the Cate-Nelson method. On the other hand, the value obtained for EDTA (1.15 mg Zn kg^?1) was comparatively lower than that calculated by applying the Cate-Nelson method.     

Comparison of Methods for Determination of Carbon in Calcareous Soils

The global cycle of carbon (C) has raised attention in recent decades due to the great increase in carbon dioxide levels (CO₂) levels in the atmosphere and its influence on climate change. Calcareous soils represent a significant fraction of the areas with potential for agriculture and have differential attributes, such as high calcium contents, magnesium, carbonates, and pH values. These attributes have been ignored in analytical procedures despite these characteristics, resulting in an overestimation or underestimation of the soil carbon. Several methods have been proposed for determining the soil carbon contents, however, studies evaluating the analytical procedures of C quantification methods, considering the soil characteristics, such as the calcareous soils, are needed, in order to improve their accuracy. Therefore, the objective of this work was to evaluate and compare methods for C determination and to propose adjustments in the methodology for calcareous soil analysis. The Yeomans and Bremner (YB) was the most efficient method for quantification of organic C among the wet oxidation methods. On the other hand, the Donagemma (WB) method underestimated the organic carbon contents. The results showed that the samples must be macerated and pretreated with a hydrochloric acid solution for the use of CHNS-O, in order to eliminate carbonates in the form of nodules and concretions.     

Automated Modification of the Molybdenum Blue Colorimetric Method for Phosphorus Determination in Soil Extracts

A flow injection analysis (FIA) method capable of automation for molybdate reactive phosphorus (P) determination in soil extracts is described. Results obtained using this method in three soil extracts [calcium chloride (CaCl₂), Olsen, and Mehlich I] were the same as those provided by the manual molybdate blue colorimetric method. Linear range extending to 2 mg P L^?1, detection limits ranging from 6 to 26 µg L^?1 depending on the soil extract, and accurate recoveries from P‐spiked samples were achieved. The sensitivity of the system was around 0.3 absorbance units per mg P L^?1, and the sampling frequency was 72 samples h^?1, higher than those described for most of the flow injection methods.     

A Rapid Acid-Oxalate Extraction Procedure for the Determination of Active Fe-oxide Forms in Calcareous Soils

Extraction with acid NH₄-oxalate is widely used to estimate the content of “active” forms of Fe oxides in soil. In calcareous soils, this extraction presents some problems (pH change, production of CO₂), which have been circumvented by decalcifying the soil before extraction. However, because of its tediousness, this procedure cannot be applied for routine purposes. In this paper, we describe a rapid procedure in which the soil is treated with oxalic acid before oxalate extraction to neutralize the active calcium carbonate equivalent. The method is simple and provides a useful estimation of the content of active Fe forms that are not occluded in the coarse particles and aggregates of carbonate.     

Microwave Digestion for Colorimetric Determination of Total Si in Plant and Mineral Samples

A new method for determining the soluble silicon (Si) concentrations in nonliquid plant and mineral samples was developed using sodium hydroxide (NaOH)–hydrogen peroxide (H₂O₂) matrix for microwave digestion (MWD-Na) followed by colorimetric Si testing. MWD-Na was compared with autoclave-induced digestion and alkali fusion. The data have shown no significant difference between these three methods. HNO₃–H₂O₂ or HNO₃?–H₂O₂?–HF microwave technique results in Si loss. The reduction of the total Si can be realized via low solubility of Si in the acid solutions or silicon tetrafluoride formation. The Mullen and Riley method for colorimetric testing of Si in a solution that uses ascorbic acid to reduce the silicomolybdate complex formed under acid conditions to an intensely blue complex was modified using iron sulfate. The combination of MWD-Na and modified colorimetric blue method provides cheap and valid data on determining the total Si in both plant and mineral samples.     

Determination of Appropriate Soil Test Extractant for Available Phosphorus in Southwestern Nigerian Soils

Evaluation of five soil phosphorus (P) extractants was done on southwestern Nigerian soils from sedimentary and basement complex parent materials to determine the relationship between the extractants and the most appropriate extractant for the soils. The soils differed in properties. Generally, soils from the basement material had less available P compared with sedimentary material. Olsen extracted the greatest P. Bray 1 measured 67% of Olsen P, Hunter measured 52%, Mehlich measured 42%, and Ambic measured 24%. Positive and significant regression (P < 0.001) existed among Bray 1, Olsen, Mehlich, Hunter, and Ambic extractants. The strongest relationship was found among Olsen, Mehlich, and Ambic P. The relationship between maize P uptake and extracted P was quadratic, whereas the relationship with Mehlich was logarithmic. Bray, Mehlich, and Olsen P were the significant contributors to the maize P uptake and dry-matter yield. Extractants in order of P extraction were Olsen > Bray 1 > Hunter > Mehlich > Ambic.     

Kinetics of Copper Desorption from Highly Calcareous Soils

Abstract

Desorption of copper (Cu) is an important factor in determining Cu availability in calcareous soils. Kinetics of native and added Cu desorption by DTPA (diethylene‐triaminepentaacetic‐acid) from 15 highly calcareous soils of southern Iran were studied in a laboratory experiment. Our results showed that two constant‐rate, Elovich, simple Elovich, and parabolic‐diffusion equations were the best‐fitted equations among eight kinetic models used. The copper desorption pattern based on the parabolic‐diffusion equation revealed that the rate of native Cu desorption was higher in the first 2 h followed by a slower release rate, which suggests that two different mechanisms are involved. The trend may describe why the DTPA soil test has been considerably successful in predicting Cu availability in calcareous soils. Stepwise multiple regression equations indicated that CCE (calcium carbonate equivalent), CEC (cation exchange capacity), and clay content are the most important soil characteristics that predict the rate constants of the kinetic models. Mean extractant recovery percentage (ERP) of the soils was only 20%, which indicated that after 20 days, DTPA extracted only one‐fifth of added Cu. Regression equations indicated that as soil OM (organic matter) content increased, the value of ERP decreased. From results reported herein it seems that CCE, CEC, and clay are the most important factors controlling Cu release from highly calcareous soils of southern Iran. However, the initial soil Cu desorption rate is probably controlled by CEC.     

Metal Extractability in Binary and Multi-metals Spiked Calcareous Soils

In the present study, a laboratory experiment was designed to compare the 0.01 M calcium chloride (CaCl₂) and diethylenetriaminepentaacetic acid (DTPA) extraction methods for their ability to predict cadmium (Cd), copper (Cu), iron (Fe), Manganese (Mn), nickel (Ni), and zinc (Zn) availability and mobility in five calcareous soils. The soils were spiked with different amounts of metals (0, 50, 100, 200, and 400 mg kg^?1) both in binary (Cu and Zn; Ni and Cd; Fe and Mn) and in multi-systems (Cd, Cu, Fe, Mn, Ni, and Zn) and incubated for 1 months at field capacity. In metal-spiked soils, both extraction methods showed a linear relationship of extractable to total metals for all soils. The fraction of total metals extracted by DTPA was much higher than the fraction extracted by CaCl₂, which was attributed to the formation of soluble metal-complexes in the complexing extracts calculated by the Visual Minteq program. DTPA extraction method showed higher selectivity for Cu over other metals both in binary and in multi-systems. Different order of metals extractability was found in binary and multi-systems for both extraction methods. Solid/solution distribution coefficient (K_d) was calculated by the ratio of the solid phase to soil solution concentration of metals extracted by CaCl₂ or DTPA extraction methods. Both in binary and in multi-systems, the average K_d (l kg^?1) of metals by soils were in the order of Mn (5398) > Fe (4413) > Zn (3376) > Cu (2520) > Ni (969) > Cd (350) in the CaCl₂-extractable metals and Fe (35) ≥ Ni (34) > Zn (18) > Mn (11.2) > Cu (6.3) > Cd (4) in the DTPA-extractable metals. Results showed that among the six studied metals, Cd had the lowest K_d, implying a relative higher mobility in these calcareous soils. The Visual Minteq indicated that in the CaCl₂-extraction method and in both binary and multi-systems the dominant species for Cu, Mn, Ni, and Zn were Cu²⁺, Mn²⁺, Ni²⁺ and Zn²⁺, respectively, while for Cd and Fe, the dominant species were CdCl⁺ and Fe(OH)²⁺, respectively.     

Transformation of Phosphate Fertilizers with Different Solubilities in Calcareous Soils

In this research work,the authors,using the recently developed method of fractionating the forms of inorganic phosphorus in calcareous soils,have studied the transformation processes of inorgnic phosphorus in three different phosphate fertilizers,i.e.,superphosphate,diammonium phosphate and calcium magnesium phyosphate,being commonly used in China,during a period of 3 years after their application to calcareous soils,and based on the experimental results obtained,some problems in current use of phosphate fertilizers are discussed.     

施加粪肥对潮土有机磷形态转化的影响

施加粪肥是提高土壤肥力的重要措施,为了解粪肥磷在潮土中的化学行为,通过室内培养试验,采用NaOH-EDTA 浸提和 31P 核磁共振技术分析比较了鸡粪、牛粪及施肥后土壤中的磷形态及含量,并研究了施肥对潮土有效磷的影响。结果表明,粪肥磷主要以无机态形式存在,2 种粪肥的有机磷形态及含量有明显不同,肌醇六磷酸在鸡粪中的含量明显高于牛粪。粪肥施加到潮土后丰富了土壤有机磷的形态。随时间延长,潮土中各形态磷发生相互转化,以肌醇六磷酸为主的正磷酸单酯含量明显降低,核酸等正磷酸双酯显著升高。鸡粪处理的土壤有效磷含量逐渐升高,牛粪处理则表现出相反的趋势。施加粪肥后,土壤有效磷呈现不同的变化规律可能是无机磷在土壤中固定或沉淀,有机磷矿化和无机磷被微生物固持这三方面综合作用的结果。     

Inorganic Phosphorus Fractionation of Highly Calcareous Soils of Iran

Abstract

Highly calcareous soils are abundant in Iran. The calcium carbonate equivalent (CCE) of these soils reach up to 650 g kg^?1. Although phosphorus (P) fertilizer is being widely used in these soils, little information, if any, is available about P status in such soils. The objectives of this study were to 1) determine inorganic P forms in 18 surface soils of southern Iran, 2) study P readsorption during different stages of fractionation schemes, 3) assess the ability of NaOH to extract aluminum (Al)‐P, and 4) evaluate the relationships between P availability indices and inorganic P forms. Eighteen soil samples with a wide range of physicochemical properties were selected for this study. Inorganic P forms was determined by sequential extraction with NaHCO₃, NH₄OAc, NH₄F, NaOH, citrate dithionite (CD), and H₂SO₄, which are referred to as Ca₂‐P, Ca₈‐P, Al‐P, Fe‐P, occluded P (O‐P), and Ca₁₀‐P. Phosphorus readsorption in different stages was determined by 1 M MgCl₂. Furthermore, a fractionation scheme without an NH₄F step was used to evaluate the ability of NaOH to extract Al‐P. NaHCO₃ (Olsen‐P) and MgCl₂‐extractable P (Exch‐P) were regarded as P-availability indices. The abundance of different P forms was in the order Ca₂‐P<Fe‐P<Al‐P<O‐P<Ca₈‐P<Ca₁₀‐P. Ca₂‐P was highly correlated with Olsen‐P and Exch‐P. Ca₂‐P, Olsen‐P, and Exch‐P showed a relationship with CCE, citrate–bicarbonate–dithionite extractable Fe (Fe_d), and Al (Al_d). Phosphorus readsorption appeared to be important only in the Ca₈‐P step, and the content of readsorbed P was related to Ca₈‐P, CCE, and clay content of the soils. In the present study, Al‐P and Fe‐P accounted for 10 and 5% of the sum of the inorganic P fractions, respectively, and Fe‐P showed a strong relationship with Fe_o, whereas Al‐P showed a significant relationship with oxalate‐extractable Al (Al_o) and Al_d. It was found that one extraction with NaOH is not a good indicator for Fe‐ and Al‐P, and the ability of NaOH to extract Al‐P was reduced with increase in Al‐P content.     

石灰性土壤有效硒浸提剂和浸提条件研究

采用外源硒加入土壤中得到硒污染土壤,6种有效硒的浸提剂NaHCO3、KH2PO4、K2SO4、EDTA、AB-DTPA和DTPA＋TEA＋CaCl2的最佳浸提时间和土液比进行了筛选,并通过盆栽试验对所选择的土壤有效硒浸提剂进行生物学校验,以找出石灰性土壤有效硒提取适宜的浸提剂及其浸提条件。结果表明,NaHCO3、KH2PO4、K2SO4、EDTA、AB-DTPA和DTPA＋TEA＋CaCl26种浸提剂有效硒浸提量都随着浸提土液比的减小而增大,且随浸提时间的增长而增大。其中NaHCO3和KH2PO4最佳土液比为1/15,振荡时间90min;K2SO4和AB-DTPA的最佳土液比为1/15,振荡时间60min;EDTA和DTPA＋TEA＋CaCl2的最佳土液比则为1/20,振荡时间30min。6种浸提剂在各自最佳的提取条件下提取的土壤有效硒量与白菜地上部分硒含量达极显著正相关,但土壤有效硒的提取量以DTPA＋TEA＋CaCl2及K2SO4最少,只占KH2PO4、AB-DTPA及EDTA提取量的14%～48%,故不适用于作为石灰性土壤有效硒的提取剂。NaHCO3适用于土壤硒含量高于5mg·kg^-1的石灰性土壤有效硒提取。KH2PO4、AB-DTPA及EDTA3种浸提剂既可提取土壤中水溶态硒,亦可提取部分的吸附态硒,提取硒数量较多,过程简单,重复性好,都可作为石灰性土壤有效硒提取的浸提剂。     

Phosphorus Use Efficiency of Wheat Genotypes Grown in Calcareous Soils

ABSTRACT

Phosphorus (P) deficiency and low P-use efficiency are induced by soil properties, especially in calcareous soils, which are dominant in semi-arid regions of the world such as the Mediterranean region. Alternative approaches to P fertilization involve exploiting plant genetics in order to achieve more efficient use of P by the growing crop. Accordingly, in a greenhouse pot experiment, we evaluated P-efficiency in wheat genotypes grown in typical calcareous soils in southern Turkey. Ten common local genotypes were grown in six soil series for eight weeks using five P application rates (0, 25, 50, 100, and 200 mg P kg^?1). Dry matter (DM) yield and P content were significantly increased by increasing P rates, with significant differences between soils. Some genotypes performed better under P stress because of better P utilization efficiency. Shoot DM was the most sensitive indicator of genetic variability under P-deficient conditions. Genotypes classified as efficient-responsive (Adana-99, 1014, Golia, Balatilla) had above average DM yield when P was not added, and responded well to P applications; efficient-non-responsive genotypes (Firat-93, Seri-82, Genc-99, Panda) had below average DM yield, but responded to P applications; inefficient-non-responsive genotypes (Fuat Bey and Ceyhan-99) had below average DM yield; and no genotypes were in the inefficient responsive category. Such P response categorization is needed for better breeding programs for nutrient-use efficiency. The study may aid in selecting P-efficient genotypes in low-P soils, especially where little P is used. The use of P-efficient genotypes should be seen as complement to, rather than a substitute for, chemical P fertilization depending on local conditions.     

Distribution of Boron in Different Fractions in Some Alkaline Calcareous Soils

Distribution of boron (B) in different fractions is still not well defined when it is applied in B-deficient alkaline calcareous soil and after harvesting of the sown crop. In the present greenhouse experiment with green gram crop, three B-deficient soils with calcium carbonate contents of 0.8 (S I), 2.1 (S II), and 4.6 (S III) percent were collected from different sites in Ludhiana and Bhatinda Districts, Punjab, India. The treatments composed of five levels of soil-applied B (0, 0.5, 0.75, 1.0, and 1.5 mg B kg^?1) soil and the experiment was laid out in Completely Randomized Design (CRD) factorial design with three replications. Mean readily soluble, specifically adsorbed, and oxide-bound B fractions got increased significantly with increase in B applications. Distribution of readily soluble B was more in low calcareous soil than in high calcareous soil. Mean values of specifically adsorbed, oxide-bound, residual, and total B were significantly more in high calcareous soils as compared to low calcareous soils. At maturity, specifically adsorbed B converted into other fractions to maintain equilibrium in soil solution. Organically bound B was greater than the oxide-bound B fraction. Among all fractions, residual fraction accounted for the major portion of the total B. Available B was negatively and significantly correlated with calcium carbonate (CaCO₃) content of soil (r = ?0.99*). At the same time, specifically bound B was also negatively and significantly correlated with readily soluble B (r = ?0.99*) whereas organically bound B was positively correlated with organic carbon content of soil (r = ?0.99*).     

Distribution of Heavy Metals in Calcareous and Non-Calcareous Soils in Spain

The distribution of chemical forms of Cd, Ni, Cr, Co, Ag, Pb, Cu, Mn and Zn in eight contaminated soils from Spain was studied using a sequential extraction procedure that fractionates the metal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible and residual forms. SEM and EDXA analysis was used to analyse the soil matrix to determine the distribution of heavy metals. The residual, reducible and carbonate-sorbed forms were dominant. Metals were generally dispersed throughout the soil matrix and could not be located by SEM-EDXA.     

Suitability of Different Soil Extractants for Determination of Available Cu and Mn Contents in Polish Soils

The aim of this study was to compare four micronutrient soil-test extractants currently in common use in Poland, Rinkis, Mehlich 3, modified Lindsay and Norvell, and Yanai, for ability to determine the plant-available concentration of copper (Cu) and manganese (Mn) in two acidic soils (pH 4.8–4.9) that had been amended with different doses of Cu and Mn fertilizers. The comparison was based on two pot experiments (each with a different soil) with corn (Zea mays), barley (Hordeum vulgare), spring wheat (Triticum aestivum), rape (Brassica napus), red clover (Trifolium pratense), and English ryegrass (Lolium perenne). The extractants were evaluated based on a correlation analysis of the microelement concentrations in plants at the end of the vegetative phase and micronutrient concentration in the fertilized soil determined by each extractant at the end of the experimental period. The largest extractable concentrations of Cu and Mn in soils were obtained with Rinkis. The modified Lindsay and Norvell soil test extracted the lowest amount of both microelements. For soil Cu, the results with the Mehlich 3 and Yanai extractants were highly correlated with the Rinkis procedure results (r = 0.98). The modified Lindsay and Norvell results were not as well correlated with Rinkis (r = 0.84). For soil Mn, the correlation of results of Yanai, Mehlich 3, and modified Lindsay and Norvell to Rinkis ranged from r = 0.80 to r = 0.86. Levels of Mn and Cu measured with each of the extractants were highly correlated with plant tissue concentrations of Mn and Cu in most of the six plant species. The exceptions to this were the following: The modified Lindsay and Norvell soil Cu levels were not correlated with ryegrass and wheat plant Cu levels; Mehlich 3 Cu was not correlated with red clover Cu; and the Rinkis-extractable Mn was not correlated with the wheat Mn. It is concluded that the Yanai and Mehlich 3 procedures are suitable alternatives to the Rinkis for Cu but not for Mn.     

Genotypic Responses of Corn to Phosphorus Fertilizer Rates in Calcareous Soils

In the Mediterranean region, much emphasis is placed on the role of fertilizers in enhancing crop production to achieve food security. Given the complex nature of phosphorus (P) reactions in soils, considerable research has dealt with fertilizer aspects related to efficient P use, but comparatively less emphasis has been given to plant variation with respect to P efficiency. In this study, selection and adaptation of P‐efficient corn genotypes was seen as one possible approach to enhancing P efficiency. Thus, a greenhouse experiment with 10 corn genotypes (traditional to modern), five P application rates (0–200 mg kg^?1), and four field trials with three genotypes for 2 years were carried out on various calcareous soils (Vertic Torrifluvent, Vertic Calciorthid, Entic Chromoxerert, and Typic Xerofluvent). Measurements were made of root characteristics. Treatments in the field trials were five P application rates as main plots (0–68 P ha^?1) and three corn genotypes as subplots. Genotypes were selected for the field trials from the greenhouse experiment as “efficient‐responsive,” “efficient‐nonresponsive,” and “inefficient‐responsive.” Dry‐matter (DM) yield and plant P uptake by plants increased with P application rates in the greenhouse experiment. Root length and mass were considerably increased by increasing P levels. Genotypes were classified for P efficiency. The studies indicated that because corn genotypes respond to P‐fertilizer application differently, this trait could be utilized to exploit native and applied P more efficiently, especially at low levels of available P and when P‐ fertilizer use is limited. This differential response derives from morphological, physiological, and genetic variability among the genotypes. Although genotypic efficiency is important for fertilizer management, the contribution of the efficiency is not a substitute for fertilizers, especially if high yields are required. Nevertheless, breeding for P‐use efficiency should be a component of any program to improve crop yield potential.     

Evaluation of Chemical Indices of Soil Pb Availability in Calcareous Soils

The objective of this study was to compare six soil tests (1 M KNO₃, 1 M NH₄OAC, 0.005 M DTPA, 0.1 M EDTA, 1 M HNO₃ and 0.025 M Ca DTPA B₄O₇) as extractants for soil Pb and as predictors of plant available Pb for wheat (Triticum aestivum L.) in the greenhouse. The soils recieved 0, 200 and 400 mg Pb kg^?1 as Pb(NO₃)₂ and are referred to as Pb₀, Pb₁ and Pb₂ treatments respectively. Of the six soil extractants, 1 M HNO₃ was the most effective extractant for Pb from Pb₀ treatment whereas 0.1 M EDTA and 0.025 M Ca DTPA-B₄O₇ were the best and equally effective in their ability to extract Pb from Pb₁ and Pb₂ treatments. Regression analysis was used to develop two variable models for predicting Pb uptake by wheat as a function of extractable Pb and selected soil properties. The 0.025 M Ca DTPA-B₄O₇ extractant was the best in predicting uptake by wheat in Pb₀ (r = 0.791^*** significant at p = 0.001) and Pb₁ (r = 0.726^***) and Pb₂ (r = 0.942^***) treatments.     

酸性土壤有效汞提取方法研究

为了更好地评价酸性土壤中汞的生物有效性和生态风险,以酸性土壤为供试土壤,通过比较国内外几种常用的土壤有效汞的浸提剂的提取效果,筛选适合于酸性土壤的有效汞浸提剂并优化相应的提取条件,从而建立酸性土壤有效汞的提取方法。结果表明,在0.1 mol·L-1HCl、1 mol·L-1NH4OAc、0.005 mol·L-1DTPA、0.03%TGA-1/15 mol·L-1Na2HPO4这4种常用浸提剂中,0.03%TGA-1/15 mol·L-1Na2HPO4是最佳的浸提剂,因为它具有最高的提取率,且其所提取的有效汞与相应稻米中Hg含量的相关性最好。0.03%TGA-1/15 mol·L-1Na2HPO4的最佳浸提条件为土液比1∶10、振荡时间120 min、振荡速度250 r.min-1,浸提出的有效汞量与油菜的相关性达到极显著相关,能较好地指示田间条件下土壤汞对作物的可给性。