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 15 毫秒
1.
Abstract

In order to better understand some of the factors likely to affect measurements of KC1 extractable acidity, experiments were conducted using synthetic solutions and extracts from a wide range of contrasting soils. The reagents used for measuring exchangeable acidity (i.e., KC1 and KF) were also examined to evaluate the effects of chemical impurities on acidity measurements. Two commonly used titrimetric methods were adapted and tested to determine the accuracy and precision of acidity measurements. The exchangeable acidity of soil extracts was investigated by extraction methods, extractant concentration, and extractant volume. Results from the soil extract experiments indicated that continuous shaking has no significant effect on acidity measurements. Filtration, however, is critical, especially for acidic organic‐rich soils, since aluminum (Al) ions can be lost during centrifugation. Extractant concentration and volume had variable effects on the acidity measurements for individual soils. In general, the modified Yuan's method is preferable to the modified Thomas’ method for estimating exchangeable Al. To ensure successful determination of exchangeable acidity, we recommend using a wider KCl:soil ratio (>15:1, v/w) for organic soils with low base saturation and allophanic Andisols. In sum, potassium chloride and potassium fluoride extraction for estimating exchangeable acidity is applicable for most soils.  相似文献   

2.
Abstract

A correction is proposed for the evaluation of salinity effects on the basis of the electrical conductivity of saturated paste extracts. It is suggested that the dilution of the soil solution during the preparation of the saturated paste must be taken into account. Equations for estimating the electrical conductivity of a soil solution at field capacity are presented. The corrected equations improve the ability to predict the salinity hazard by determining the electrical conductivity of saturated paste extract.  相似文献   

3.
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   

4.
Abstract

Studies were conducted to determine the reliability of four techniques for prolonged pH monitoring of small containers of media. Correlation coefficients of the methods tested (with saturated paste) were 0.96, 0.95 and 0.92 for porous cup solution extract, container effluent and placing the electrode directly in media, respectively. Continued coring for saturated paste determinations reduced fern growth by 38% during the period of study.  相似文献   

5.
Saline–sodic and sodic soils are characterized by the occurrence of sodium (Na+) to levels that can adversely affect several soil properties and growth of most crops. As a potential substitute of cost‐intensive chemical amelioration, phytoremediation of such soils has emerged as an efficient and low‐cost strategy. This plant‐assisted amelioration involves cultivation of certain plant species that can withstand ambient soil salinity and sodicity levels. It relies on enhanced dissolution of native calcite within the root zone to provide adequate Ca2+ for the Na+ Ca2+ exchange at the cation exchange sites. There is a lack of information for the Na+ balance in terms of removal from saline–sodic soils through plant uptake and leaching during the phytoremediation process. We carried out a lysimeter experiment on a calcareous saline–sodic soil [pH of saturated soil paste (pHs) = 7.2, electrical conductivity of the saturated paste extract (ECe) = 4.9 dS m−1, sodium adsorption ratio (SAR) = 15.9, CaCO3 = 50 g kg−1]. There were three treatments: (1) control (without application of a chemical amendment or crop cultivation), (2) soil application of gypsum according to the gypsum requirement of the soil and (3) planting of alfalfa (Medicago sativa L.) as a phytoremediation crop. The efficiency of treatments for soluble salt and Na+ removal from the soil was in the order: gypsum ≈ alfalfa > control. In the phytoremediation treatment, the amount of Na+ removed from the soil through leaching was found to be the principal cause of reduction in salinity and sodicity. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

6.
Abstract

Selenium (Se) has been recognized as an element of environmental concern because of its natural occurrence and potential toxicity to plants, animals, and humans. Range and coal mine (reclaimed and abandoned) soils were studied using various soil extracts, including saturated paste, hot water, ammonium bicarbonate‐DTPA (AB‐DTPA), and phosphate in order to compare the Se extraction efficiency of these reagents and to characterize the soil‐plant Se correlations in these environments. Soil extraction data indicated the order of Se extractability was phosphate > AB‐DTPA > hot water > saturated paste. The saturated paste‐extractable Se was found to be typically very low. Statistically significant correlations between phosphate‐, AB‐DTPA‐, and hot water‐extractable Se were observed irrespective of the type of environment. Selenium extracted by these reagents indicated certain relationships, such as phosphate ≈ 2 AB‐DTPA, phosphate ≈ 5 hot water, and AB‐DTPA ≈ 3 hot water. Selenium content of shrub vegetation was approximately half of that of grass and forb. Soil‐plant Se correlations were found to be dependent on land type as well as vegetation type; the regressional values for soil suitability limit (SSL) of Se corresponding to 5 mg/kg plant Se varied accordingly. For a particular type of vegetation, the SSL values followed the same order as the extraction efficiency of the different reagents. The AB‐DTPA‐extractable Se was found to be the best predictor of soil‐plant Se correlations under field conditions, though phosphate‐, hot water‐, and saturated paste‐extractable soil Se were also related to the Se concentrations in different types of vegetation. Selenate was found to be the potential aqueous specie for plant uptake. A comparison of different soil environments containing various vegetation types also suggested that, for a plant containing 5 mg/kg Se, the soil Se status would be highest in abandoned mine lands, followed by reclaimed mine and undisturbed range environments, respectively.  相似文献   

7.
Abstract

A second derivative UV‐spectrometry method is described for the determination of nitrate in soils. Ammonium, nitrite, and urea may be determined in the same extract. The method generally requires no pretreatment of soil extracts, and hence is very rapid. It is largely free from interferences. Recoveries of added nitrate in four soils by the proposed method compared favourably with the phenoldisulphonic acid method.  相似文献   

8.
Abstract

Turbidimetric methods, using Ba ions to precipitate SO4, are frequently used to determine soil sulfates extracted with phosphate solutions. These methods, as routinely performed, seriously underestimate SO4 in some soils of the tropics because phosphate is removed from the extractant by soil adsorption and because many extracts fail to yield satisfactory precipitate even if the extracting procedure is adequate. Decolorizing the extracts with carbon black, treating extracts with strong oxidizing agents, adding SO4 spikes, and seeding the extracts with BaCl2 seed‐crystals improve precision, but some extracts, especially those from soils derived from volcanic ash, do not yield reliable precipitates even though these procedures are employed. This paper presents a method that consistanlty yielded more SO4 than other turbidimetric procedures with which it was compared. The proposed method was further validated against an ion‐chromatographic method for SO4 determination. The two methods yielded virtually identical results.

The proposed method consists of extracting SO4 with 0.04 M Ca(H2PO4)2 pH 4, at a soil‐to‐solution ratio of 1: 10. Repeated extraction is necessary for phosphate‐retentive soils. (A. single extraction was approximately 40% effective for removing indigenous SO4 from a Hydric Dystrandept subsoil, approximately 78% effective for an Eutrustox.) Organic materials are removed from the extracts by adsorption on charcoal; SO4 is concentrated in the extract by volume reduction; a SO4 spike is added; BaCl2‐seed crystal is added, after which volume is increased by adding BaCl2 solution. Optical density is read at 600 nm.  相似文献   

9.
Abstract

An extraction procedure for potted crop media is proposed which removes under vacuum a solution from an intact pot. The vacuum extracted solution had nitrate and potassium concentrations and conductivity lower than a solution obtained by saturated paste extract procedure. A high correlation between the conductivity of solution obtained by vacuum and saturated paste extract methods permitted an interpretation of the vacuum extraction results based on ranges suggested for a saturated paste extract.  相似文献   

10.
Abstract

Soil salinization and sodication affect large areas of agricultural land in the world. Amelioration of these soils to make them suitable for agricultural production depends on understanding sodium dynamics and chemical interactions governing nutrient availability. Three locations in eastern Croatia were characterized to the 5‐m depth. The two solonetz‐solonchak soils were alkaline, whereas the solonetz soil had near‐neutral A/E horizon and alkaline deeper horizons. Electrical conductivity of the saturated extract (ECe) was greater than 4 dS m?1 in the top horizons in the solonetz‐solonchak soils. The solonetz soil had 2.8–4.7 dS m?1 in shallow A/E, CG, and G horizons and up to 6.3 dS m?1 below 1.5 m. Highly alkalinized sodic horizons (exchangeable sodium percentage, ESP >20) had 24–47% Ca2+ and 27–33% Mg2+ on the cation exchange complex. Sodium adsorption ratio (SAR) was high (18–26) in the P horizon and even more so in Bt,na horizon (35–36) of solonetz‐solonchak soils. A strong negative exponential relationship existed between soluble Ca2+ and SAR (SAR increased greatly when Ca2+ dropped to around 3 mg dm?3). An increase in pH to greater than 8.4 resulted in an exponential increase in SAR. Leaching of Na+ with successive volumes of water was similarly effective for the P and Bt,na horizons in the solonetz‐solonchak soils, but SAR remained greater than 15 even after six successive cycles of leaching. In conclusion, extensive amelioration of tested soils with gypsum and leaching will be required to overcome poor physical and chemical characteristics caused by various degrees of alkalization and sodication to bring these soils into production.  相似文献   

11.
Electrical conductivity (EC) was measured on extracts from four different types of compost using two different dilution techniques. When EC was measured on extracts obtained using a saturated paste method, EC varied by 20-25% of the mean measurement. When EC was measured on extracts obtained using a quantitative dilution procedure over a range of dilution ratios, EC varied by less than 10% of the mean. For dilution ratios less than 8 (ml water/g dry compost), the increase in EC was less than expected, suggesting that at the lower dilution ratios salts were incompletely extracted or did not completely diffuse from the particle interior to the extractable solution. A method of comparing compost EC measurements obtained using different dilution ratios, including the saturated paste dilution, is presented. This method predicted the EC of the saturated paste extract in three of the four compost samples tested. These methods could be integrated into a computer data spreadsheet for a typical composting operation. Thus, this work has implications for better sampling techniques and simpler analyses for estimating the EC of compost samples.  相似文献   

12.
Groundwater contaminated with sulfate (SO4 2‐) at concentrations higher than allowable for drinking water might still be usable for irrigation. Objectives were to determine the growth response and mineral uptake of two forage crops irrigated with waters containing SO4 2‐ at concentrations ranging from 175 to 1743 mg/L, and with electrical conductivities (EC) ranging from 1.2 to 3.6 dS/m. Plants were grown for 12 weeks in 8‐L pots containing a calcareous sandy loam and were harvested at 4, 8, or 12 weeks for plant growth measurements and tissue analysis. Digested leaves, stems, and reproductive tissues were analyzed by inductively coupled plasma (ICP) spectroscopy at each harvest, as were saturated soil paste extracts. Shoot growth of tall fescue (Festuca arundinacea Schreb.) was not affected by irrigation water treatment, whereas shoot growth of alfalfa (Medicago sativa L.) was increased by a moderate level of soil solution SO4 2‐ Sulfur (S), boron (B), magnesium (Mg), sodium (Na), and zinc (Zn) concentrations in shoot tissues of both species showed a tendency to increase with increasing SO4 2‐ content of irrigation water. Shoot tissue concentration of molybdenum (Mo) increased with maturation in both species, while the concentrations of B, potassium (K), manganese (Mn), Na, and Zn decreased. Soil saturated paste extract concentrations of Mg and Na increased with irrigation water Mg and Na concentrations, while Ca and S concentrations in the soil solution became saturated at the higher irrigation water concentrations of these elements.  相似文献   

13.
Soil sodicity is an increasing problem in arid‐land irrigated soils that decreases soil permeability and crop production and increases soil erosion. The first step towards the control of sodic soils is the accurate diagnosis of the severity and spatial extent of the problem. Rapid identification and large‐scale mapping of sodium‐affected land will help to improve sodicity management. We evaluated the effectiveness of electromagnetic induction (EM) measurements in identifying, characterizing and mapping the spatial variability of sodicity in five saline‐sodic agricultural fields in Navarre (Spain). Each field was sampled at three 30‐cm soil depth increments at 10–30 sites for a total of 267 soil samples. The number of Geonics‐EM38 measurements in each field varied between 161 and 558, for a total of 1258 ECa (apparent electrical conductivity) readings. Multiple linear regression models established for each field predicted the average profile ECe (electrical conductivity of the saturation extract) and SAR (sodium adsorption ratio of the saturation extract) from ECa. Despite the lack of a direct causal relationship between ECa and SAR, EM measurements can be satisfactorily used for characterizing the spatial distribution of soil sodicity if ECe and SAR are significantly auto‐correlated. These results provide ancillary support for using EM measurements to indirectly characterize the spatial distribution of saline‐sodic soils. More research is needed to elucidate the usefulness of EM measurements in identifying soil sodicity in a wider range of salt and/or sodium‐affected soils.  相似文献   

14.
Abstract

A method for determining the relative proportions of inositol isomers present in soil as their pentakis‐ and hexakisphosphate derivatives (IP5 + IP6) is presented. The method involves determination of the isomers as their hexakis‐O‐acetyl derivatives by gas‐liquid chromatography. The only isomers detected in extracts of 4 soils were chiro‐inositol, neo‐inositol, myo‐inositol and soyllo‐to‐inositol. Little variation in the relative proportions of the isomers was found between the 4 soils but the relative proportion of the neo‐isomer was considerably greater than previously published estimates. The method also makes possible the estimation of the (IP5 + IP6) fraction, using anion‐exchange chromatography on a aliquot of the extract.  相似文献   

15.
Abstract

In a study with fifty peaty growing media some water extracts were tested on their ability to estimate the chemical composition of the “soil”; solution. The chemical and physical characteristics of the growing media differed widely. The soil solution was prepared by pressing out 30–50% of the the water from the growing media exactly brought on a water content equal to the water content at a pressure head value of‐1.0 kPa. The water extracts compared were, the press extract of growing media brought by a quick method on a water content at a pressure head of‐1.0 kPa and an extract prepared from a 1:1.5 (v/v water/growing medium) suspension. In the extracts all the likely anions and cations were determined. The correlation coefficients for the relationships between the analytical data of the soil solution and the analytical data of the extracts varied between 0.975 and 0.993 for the extract prepared from the media quickly brougt to a water content at a pressure head of‐1.0 kPa and between 0.912 and 0.992 for the extract prepared from a 1:1.5 suspension. So both extracts are a suitable aid to estimate the chemical composition of the soil solution. The extraction methods compared are discussed on their suitability for routine soil testing purposes. An overall view for the interpretation of the analytical data is presented.  相似文献   

16.
Abstract

Existing colorimetric methods for determining phosphorus (P) in citrate‐bicarbonate‐dithionite (CBD) extracts from soils and sediments require pretreatments of extracts prior to the determination of the element. A method is proposed for the determination of P in CBD extracts without any chemical treatments. Maintaining the citrate concentration below 2.4 mM, maximum and stable absorbance develops in P‐Mo‐Sb system within one hour and remains stable for 20 hours. An evaluation of potential interference was made by adding varying amounts of P to CBD extracts over a range of extractable iron (Fe) and aluminum (Al) levels. Near 100 percent recovery of the added P suggests the applicability of the method to soils and sediments. Major advantages of the method are speed, simplicity, reliability and stability of the colored complex.  相似文献   

17.
Summary

A simple, single‐step extraction with LiEDTA for the estimation of CEC and exchangeable bases in soils has been developed. Multivalent cations are stripped from the soil adsorption sites by the strongly chelating agent EDTA, and are replaced by Li. In soils without CaCO3 or water soluble salts, exchangeable divalent cations (Ca, Mg) are chelated by EDTA and exchangeable monovalent cations (Na, K) are replaced in a single extraction step using 0.25–2.5 g of soil and 10.0 ml of extractant.

In calcareous soils the CEC can be determined in the same way, but for the extraction of exchangeable Ca and Mg, another separate extraction is needed because dissolution of calcite by EDTA is unavoidable. This extraction is done with as much NaEDTA as needed to extract only exchangeable Ca and Mg in a 1:2 (m/V) soil/alkaline‐50% (V/V) aethanolic solution to minimize dissolution of calcite.

In gypsiferous soils gypsum is transformed into insoluble BaSO4 and soluble CaEDTA by LiBaEDTA thus avoiding interference of Ca from dissolution of gypsum, which renders the traditional methods for determining CEC unsuitable for such soils. To determine exchangeable Ca and Mg, Na4EDTA is used as for calcareous soils.

In saline/sodic soils replacement of Na by Li is incomplete but the Na/Li‐ratio at the complex after extraction is proportional to the molar Na/Li‐ratio in the extracts, so that the CEC and original exchangeable sodium (ESP) content can be calculated. Additional analysis of Cl and, if necessary, SO4 in the extracts of saline soils can be used to correct for the effect of dissolution of the salts on the sum of exchangeable cations.

This new method is as convenient as the recently developed AgTU (silverthiourea), but is better suitable for calcareous and gypsiferous soils.  相似文献   

18.
Abstract

The effects of irrigating with saline water on native soil fertility and nutrient relationships are not well understood. In a laboratory experiment, we determined the extent of indigenous nutrient [calcium (Ca), magnesium (Mg), potassium (K), manganese (Mn), and zinc (Zn)] release in salt-saturated soils. Soils were saturated with 0, 75, and 150 mmolc L?1 sodium chloride (NaCl) solution and incubated for 1, 5, 10, and 15 days. The saturation extracts were analyzed for pH, ECe, and water‐soluble Ca, Mg, K, Mn, and Zn, and the remainder soil samples were analyzed for exchangeable forms of these elements. In a subexperiment, three soil types (masa, red‐yellow, and andosol) were saturated individually either with 100 mmolc L?1 of NaCl, sodium nitrate (NaNO3), or sodium sulfate (Na2SO4) salt. These salts were also compared for nutrient release. Soils treated with NaCl released higher amounts of water‐soluble than exchangeable nutrients. Except for Zn, the average concentrations of these nutrients in the soil solution increased significantly with time of incubation, but concentrations of the exchangeable forms varied inversely with time of incubation. The masa soil exhibited the highest concentrations of Ca and Mg, whereas K was highest in andosol. The extract from soils treated with NaCl contained greater amounts of soluble cations, whereas soils treated with Na2SO4 produced the lowest concentration of these elements irrespective of the type of soil used.  相似文献   

19.
Abstract

The efficiency of extraction of nitrate with saturated CaSCO4 solution and with IM KCl was compared for a range of field‐moist and air‐dried soils. Saturated CaSO4 was as effective for moist soils and slightly more effective for dried ones, and removed 95% of the nitrate after shaking for 5 min. Three methods of nitrate analysis using an ion‐selective electrode were compared with continuous‐flow analysis (CFA). All gave good correlations with CFA but only one, a “known addition” method, gave results which agreed quantitatively. This method could be applied at nitrate‐N concentrations at least as low as 0.5 mg kg‐1.  相似文献   

20.
The integrated effect of irrigation and agricultural practices on soil salinity in the Jordan Valley （JV）, where over 60% of Jordan’s agricultural produce is grown, was investigated in this study during 2009-2010. Due to the differences in agricultural operations, cropping patterns, irrigation management, and weather conditions, 206 top- and sub-soil samples were taken every 1 to 3 km from representative farms along a north-south （N-S） transect with 1 to 2 km lateral extents. Soil electrical conductivity of saturated extract (ECse), Ca, Mg, K, Na, Cl, and Na adsorption ratio （SAR） were determined in saturated paste extracts. Results indicated that about 63% of soils in the JV are indeed saline, out of which almost 46% are moderately to strongly saline. Along the N-S transect of the JV, ECse increased from 4.5 to 14.1 dS m-1 in top-soil samples. Similar increase was observed for the sub-soil samples. The major chemical components of soil salinity; i.e., Ca, Mg, and Cl, also showed a similar increase along the N-S transect of the valley. Moreover, compared to previous field sampling, results showed that changes in soil salinity in the JV were dramatic. In addition, it was found that Cl imposed an existing and potential threat to sensitive crops in 60% of the soils in the JV, where Cl concentrations were greater than 710 mg L-1. Under the prevalent arid Mediterranean conditions, improving the management of irrigation water, crops, and nutrient inputs and increasing water and fertilizer use efficiencies should be indispensable to conserve and sustain the already fragile agricultural soils in the JV.  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