Electro-ultrafiltration Research Articles

Sulfur in Ghanain soils

Sulfur availability in twenty selected surface soils (0–22 cm), which varied in both physical and chemical properties and sampled under cultivated and uncultivated management in the various ecological zones of Ghana, was studied. Texture varied from coarse sand to clay, with 16–85% sand and 10–51% clay. Organic C varied from 0.45 to 2.24% and total N from 0.034 to 0.215%; soil pH (0.01M CaCl2) from 3.69 to 7.43 and total S from 44 to 273 ppm. Inorganic sulfate formed 2.3 to 14.8% of the total S, HI-reducible S 4.4 to 28.2, C-bonded S 4.4 to 28.2 and unidentified organic S 12.7 to 63.2%. Sulfur availability was assessed by chemical extraction methods and electroultrafiltration technique as follows: (i) extraction with Ca(H2PO4)2·H2O solution containing 500 ppm P, (ii) extraction with 0.1M LiCl and (iii) electroultrafiltration (EUF) at 80°C, 400 V for 10 min and also on seven of the soils the standard EUF fractionation procedure of Nemeth. Ca(H2PO4)2-extractable S was not significantly correlated with LiCl-extractable S nor with any of the EUF values. LiCl-extractable S was not significantly correlated with sulfate extractable by and EUF−1+2+3 fractions (r=0.911**). Dry matter yield of oat seedlings and EUF−1+2+3 fractions (r=0.911**). Dry matter yield of oat seedlings was not correlated with any of the availability indexes. Total S uptake was significantly correlated with LiCl-extractable S (r=0.629** without S and 0.729** with S applied) and with EUF-80°C, 400 V/10 min (r=0.561**), EUF-1 (r=0.953***) and EUF-2 (r=0.912**). On all the soils, more S was taken up by oat plants than could be accounted for by the inorganic S and S mineralized from organic S during an incubation period of 4 weeks.

Organic nitrogen compounds extracted from arable and forest soils by electro-ultrafiltration and recovery rates of amino acids

Extraction of synthetic amino acids dissolved in water by means of electro-ultrafiltration (EUF) showed average recovery rates of about 75%. Higher losses were obtained, particularly with cysteine, methionine and NH44; the latter, probably being deprotonated at the cathode, may be lost in form of NH3. The EUF extracts of three arable and two forest soils were investigated for their N compounds. In the arable soils only about 3% of the total organic N extracted by EUF was free amino acids; about 23%–55% consisted of amino N (hydrolysable N) and the rest was non-hydrolysable N. The two forest soils contained higher amounts of EUF-extractable organic N compared with the arable soils. In the two forest soils the content of free amino-acid N amounted to 8% and 11% of the EUF organic N, and the proportion of hydrolysable N from total EUF-organic N was 41% and 46%. It is suggested that the amino-acid N and the hydrolysable N can be easily mineralized.

Determination of phytotoxic soil aluminium by electroultrafiltration

AbstractThe experiments address the questions of whether phytotoxic Al can be determined by electroultrafiltration (EUF). Spring barley (Hordeum vulgare) was grown in pot experiments on 28 soils differing widely in their characteristics. Al toxicity was measured in terms of root parameters and top growth. On soils rich in EUF extractable Al typical Al toxicity symptoms were found in roots and tops. EUF extractable Al obtained at the cathode (EUF‐Al, cathode) was correlated with root fresh weight (R2 = 0.554), root length (R2 = 0.653), root diameter (R2 = 0.729) and fresh weight of tops (R2 = 0.681). The Al obtained at the anode was not correlated with any of these plant parameters. It is supposed that this anionic Al consists of non toxic organic Al complexes. Correlations between plant parameters and KCl‐exchangeable Al were less close than those for EUF‐Al (cathode). Correlations between soil pH and plant parameters were in between the correlations for exchangeable Al and EUF‐Al (cathode).

A comparative study of the soil zinc fractions determined by chemical methods and electro-ultrafiltration (EUF) and their relations to zinc nutrition in rice

Rice (IR 42) was grown on two soils differing in zinc status for 30 days with and without Zn under submerged conditions in pots. The fate of soil zinc was characterized by extraction of the soil successively with copper acetate and sodium hypochlorite and by EUF extraction. Most of the applied zinc was extracted by copper acetate and represented as complexed fraction. There exists a close and significnat relation between Cu(OAc)2-extractable zinc and Zn extracted by EUF for 5 minutes at 50 volts (r=0.98). The EUF-extractable zinc and Cu(OAc)2-extractable zinc were significantly correlated with the zinc content in the plant (r=0.82). The data from this investigation suggest the possibility of Zn fractionation with the EUF technique and the fractions obtained agree closely to those determined by chemical methods. The results obtained indicate that Zn in soil is held by weak organic bonding and that the extractions by Cu(OAc)2 and/or EUF-5 minutes serve as a useful basis for extimating zinc availability in rice soils.

The Effect of Calcium and Magnesium on Soil Nitrate Determination by Automated Segmented‐flow Methods

AbstractAn automated procedure, involving the reduction of NO‐3 to NO‐2 by an alkaline solution of hydrazine sulfate containing traces of Cu2+, is commonly used for determination of small quantities of NO‐3‐N in electro‐ultrafiltration (EUF) extracts of soils. When this reduction method was employed to determine NO‐3‐N in aqueous extracts from certain Calciaquolls, low and erratic results were obtained with 24 of 46 soil samples. The problem extracts contained high levels of Ca2+ and Mg2+ that interfered with the method. Soil extracts with <40 mg Ca2+ L−1 and 15 mg Mg2+ L−1 presented no analytical problems. Placement of a cation exchange resin column between the sampler and pump of a Technicon AutoAnalyzer II overcame the interference, due presumably to removal of Ca2+ and Mg2+ from the flow line. Solution studies revealed that Ca2+ and especially Mg2+ prevented quantitative reduction of NO‐3 to NO‐2. No analytical problems were encountered with any of the soil extracts when a Cd‐Cu column was used to reduce NO‐3 to NO‐2. Any hydrazine sulfate reduction method should be carefully evaluated when newly introduced as an analytical procedure for soil NO‐3‐N determination.

Characterizing the dissolution of phosphate rock materials by electro-ultrafiltration

Electro-ultrafiltration (EUF) was evaluated as a potential technique for characterizing the dissolution and assessing the chemical reactivity of contrasting phosphate rock (PR) materials. The types of rock used were: three reactive rocks, Sechura phosphate rock (SPR), North Carolina phosphate rock (NCPR), and Chatham Rise phosphorite (CRP), which contains significant amounts of calcium carbonate; one unreactive rock, Tennessee phosphate rock (TPR); and one iron and aluminium phosphate, calcined Christmas Island “C” grade phosphate rock (Calciphos). Dissolution of SPR increased as the solution:solid ratio increased to 250:1, the voltage was increased from 0 to 400 V, and the ionic strength of the extracting solution was increased. The neutralizing effect of any CaCO3 present in PR materials, which is a major limitation with single chemical extraction procedures, does not appear to be a problem with EUF. A limitation of using de-ionized water as the extracting solution with EUF is the small amounts (1 to 6%) of total of P extracted. Addition of NaCl to the extracting solution increased the dissolution of all PR materials, although this varied with the PR. With both de-ionized water and NaCl as the extracting solution, EUF was inferior to 2% formic acid for assessing agronomic effectiveness of the PR materials. EUF appears to be of limited value in assessing the chemical reactivity of PR materials.

SOLUTION, EXCHANGEABLE, AND NONEXCHANGEABLE POTASSIUM IN FIVE SOIL SERIES FROM THE ALLUVIAL SOILS REGION OF NORTHERN INDIA

We investigated soils belonging to five soil series from the alluvial belt of northern India. These series differed in their solution, exchangeable, and nonexchange- able potassium (K). Potassium desorbed by electroultrafiltration (EUF) in 10 min (EUF-10) was almost equal to water-soluble K (1:5 soil water extract). Potassium desorbed by EUF in 35 min (EUF-35) was less than ammonium-acetate-extractable K (NH4OAc), which was much less than boiling nitric-acid-soluble K (reserve). Water-soluble K was 17 to 30% of NH4OAc K, which, in turn, was 6 to 16% of reserve K. Soils with high amounts of exchangeable K and percentage of K saturation recorded higher amounts of K in solution. At constant exchangeable K, the water-soluble K in the Nabha series was almost double that of the Khatki and Rarha series. The Khatki and Rarha series with comparatively heavier texture had high reserve K, although the rate of release of K was low. The Nabha series with comparatively less reserve K had the highest rate of K release. The Lukhi series, low in both NHjOAc and reserve K, had an intermediate rate of K release. The Nabha soils, with the maximum rate of K release, are expected to deplete much faster than the Khatki and Rarha series that have high reserves of K, but slow rates of release.

COMPARATIVE POTASSIUM LEVELS REMOVED FROM SOILS BY ELECTRO-ULTRAFILTRATION AND SOME CHEMICAL EXTRACTANTS

The objective of this study was to compare extractable potassium levels removed from soils by electro-ultrafiltration (EUF) and by conventional chemical soil tests. Accordingly, concentrations of potassium removed from soils by three EUF and six chemical extraction procedures were compared, on a group of 50 soils which contained less than 20% clay and on a second group of 52 soils which contained from 20 to 50% clay, by means of regression and correlation techniques. The following three EUF extraction procedures were tested: (i) 50 V at 5-min; (ii) 50 V at 5-min plus 200 V at 25-min; and (iii) 300 V at 15-min. Results indicated that the concentrations of soil K found in the combined anolyte and catholyte of the EUF or removed by the chemical procedures were very closely related (r-values generally greater than 0.90). However, EUF was less efficient in removing K from soils containing higher proportions of clay than NH4OAc, the new Mehlich solution, or the double acid mixture used at 1:30 wt/vol soil-solution ratio. As soil K fractions extracted by different EUF procedures were closely related among themselves as well as between the chemical methods tested, EUF would not provide soil fertility information that could not be obtained by less laborious and expensive chemical procedures. Key words: Soil testing, NH4OAc, double acid, new Mehlich extractant, electro-ultrafiltration

Extraction of easily soluble fractions of Fe and other heavy metals from various substrates by electro-ultrafiltration (EUF) and their relation to the heavy-metal contents of plants

Easily soluble heavy-metal fractions from different soils, a garbage-sewage sludge compost and peat were extracted by EUF. Blanks were determined by extracting distilled water. As the rubber seal of the extraction chamber contained Zn, the obtained Zn values were not reliable. The relative standard deviations of extracted micronutrients were 29.1% for Fe and 20.5% for Mn, Fe, Mn, Zn, Cu, Pb, Cd and Cr were not only found in the filters but also in the extracts.

The effect of P source on P desorption by electro-ultrafiltration (EUF) on two different soils

The effect of P source on P desorption by electro-ultrafiltration (EUF) on two different soils

Application of electro-ultrafiltration (EUF) in agricultural production

Application of electro-ultrafiltration (EUF) in agricultural production

Use of electroultrafiltration (EUF) method for investigating the behaviour of phosphate fertilizers in tropical soils

The solubility of superphosphate and rock phosphate was studied in six soils differing widely in pH, clay content, and type of clay minerals. Soils were incubated with increasing amounts of phosphate fertilizer for 1, 4, 12, and 24 weeks at 60% maximum water capacity and then extracted by means of electroultrafiltration (EUF). In the acid soils (pH-H2 O: 4.3 to 5.6) the phosphate quantities extracted did not differ much between fertilizer types. In the neutral soils (pH-H2 O: 6.6 to 6.9) 2 to 10 times as much was extracted from the superphosphate treatments as from the rock phosphate treatments. A fractionated EUF extraction (change of extraction time and voltage) showed that in the acid soils, rock phosphate was more soluble than superphosphate, but in neutral soils the opposite was true. In five of the six soils investigated the solubility of superphosphate declined during an incubation period of 24 weeks, whereas the solubility of rock phosphate showed no clear trend in relation to the time of incubation.

Evaluation of the nutrient dynamics in calcareous soils from Pakistan by electro-ultrafiltration (EUF)

Abstract The nutrient fractions of soils rich in CaCO3 from Punjab (Pakistan) were determined by means of electro-ultrafiltration (EUF) as well as by conventional methods. The following results were obtained. At relatively high AL-P2O5 values, the P values obtained by the Dutch water method were comparatively low and indicated an insufficient P supply. Great differences existed between the AL-P2O5 and CAL-P2O5 values which signalled the presence of barely soluble Ca phosphates. This explained the low water soluble P values of these soils. The effectively available EUF-P values obtained at 20°C and 200 V within 30 min were considerably higher than the water soluble P values and indicated a medium to good P supply. The effectively available EUF-K amounts at 20°C were lower than the contents of exchangeable K, indicating that these soils bind K ions selectively. Depending on the degree of selectivity, the EUF-K values at 20°C can be very different at almost equal contents of exchangeable K (cf. Table 2, Nos. 1 and 7). An amount of effectively available K obtained by EUF at 20°C, e.g. 14 mg, can therefore be released from these soils at contents of exchangeable K in the range of 16–31 mg (Table 2, Nos. 1 and 6).

Use of the electroultrafiltration (EUF) technique to study the potassium dynamics of wetland soils and potassium uptake by rice

Abstract Potassium uptake by rice was studied in relation to the K dynamics of two soils (Pili clay and Maligaya silty clay loam) from the principal rice growing provinces in the Philippines (Camarines Sur and Nueva Ecija). The K dynamics were determined by means of the EUF technique and by establishing the K buffer capacities of both soils. Although the Maligaya silty clay loam was higher in exchangeable K, the K uptake by the crop, particularly at the early growing stage, and the K concentrations of the young crop were higher in the Pili clay. This was consistent with the EUF extractable soil K (EUF-K), indicating that the EUF-K was a better indicator of K availability than the exchangeable K. The Maligaya silty clay loam showed a higher K buffer capacity than the Pili clay. This higher K buffer capacity also contributed to higher K uptake, especially during the later growth stage. Maximum grain yields, however, were obtained when the value of the Total EUF-K Fractions was above 40 ppm K at the maximum ...

Rice yield in relation to electroultrafiltration extractable soil potassium

Potassium in wetland rice soils from five different locations in the Philippines was analyzed using the electroultrafiltration (EUF) technique and by extraction withN NH4 acetate (pH 7). The soils contained low exchangeable K and responded to K application. The K soil test values were calibrated against the rice response to K application under field conditions. EUF extractable soil K correlated highly significantly with the rice yield response to K fertilizer, whereas the NH4 acetate extractable K (exchangeable K) did not. Under limiting K supply in soils, rice yield depends more on the EUF-K than on the exchangeable K. Maximum grain yields were obtained when the EUF-K values after harvest and before wetland preparation were above 30 ppm K.

Cupric acetate as an extractant for the estimation of plant available zinc in wetland rice soils

Abstract Availability of Zn in zinc‐deficient flooded rice soils with and without zinc application was evaluated by chemical methods and by electro‐ultrafiltration (EUF). Both Cu(OAc)2 and EUF extractions showed highly significant correlations with zinc concentration in the rice plant and with plant dry matter. Cu(OAc)2 appears to be a simple and effective extractant for determining zinc availability to the rice plant. Dilute acid (HCl, 0.05 mol/1) extractable zinc from nearly neutral and alkaline soils, was not significantly correlated either with Zn content in the rice plant or with plant dry matter.

Desorption of cations from scottish soils by electro‐ultrafiltration

AbstractSoil cations were desorbed by electro‐ultrafiltration (EUF), i.e. by applying an external electric field to aqueous suspensions, and collecting the cations by ultrafiltration. Three different field strengths were used to obtain several cation fractions in a single extraction run lasting 35 min. Potassium desorbed in 10 min (K10) was closely correlated with the equilibrium activity ratio (AR0) of soil K measured in 0.01M CaCl2, for all but the sandy loam soils, while that desorbed in 35 min (K35) was less than the exchangeable K, but correlated closely with it. EUF values compared favourably with other soil K parameters, determined by conventional methods, for predicting uptake of K by rye‐grass from ten soils during intensive cropping in the glasshouse. Sodium desorbed in 35 min (Na35) approximated to the exchangeable Na, although most of it was desorbed in the first 15 min. Na10 and Na35 accounted for about 56% of the variation in Na uptake by ryegrass at the first cut, and 68% of the variation in the cumulative uptake at the sixth cut. Between 9–24% of the exchangeable calcium was desorbed in 35 min, and magnesium desorbed was closely correlated with both the Mg concentration of the soil saturation extract and the exchangeable Mg. EUF extraction of Mg is less satisfactory than for K, Na and Ca owing to the precipitation of Mg(OH)2 on the cathode filter.

Determination of categories of soil nitrogen by electro-ultrafiltration (EUF)

The determination of N fractions in the soil by means of electro-ultrafiltration (EUF) is described. The results can be summarized as follows: The EUF procedure gives improved insight into the N dynamics of a site and this should serve as a basis for N-fertilizer recommendations.

The use of rate equations for a quantitative description of K desorption from soils in an external electric field (electro‐ultrafiltration)

AbstractIons can be extracted from soils by applying an external electric field to a soil suspension. When a constant field strength is employed characteristic desorption parameters can be calculated from the results, such as maximum desorbable quantity, halftime, and rate constant. The method consists of a combination of electrodialysis and ultrafiltration and is called electro‐ultrafiltration (EUF).It was found that the K transfer from the central compartment A to the cathode compartment B follows a first order rate law, if compartment A contains only the solution of a strong electrolyte such as KCl. If a soil suspension is introduced into compartment A the bulk of K that is transferred to compartment B has first to be desorbed from the soil particles hence the designation as desorption for the transfer from a soil suspension. In this case a second order rate law is followed.The rate equations allow the calculation of the quantity of K involved in the desorption process and the rate with which it is released. It was found that invariably only the exchangeable K takes part in the desorption reaction. The desorption rate differs between soils and depends on clay content and the quantity of exchangeable K present in the soil. It is suggested that the desorption data may provide a means of describing the soil K status by kinetic parameters.

Q/I relations and electroultrafiltration of soils as measures of potassium availability to plants

AbstractThe equilibrium activity ratio (ARo) of soil potassium and the K extracted by electroultrafiltration (EUF) within a desorption time of 10 min (EUF10) were compared as measures of K availability indicated by K uptake and dry matter yield of barley plants grown in four soils receiving different rates of K fertilization in a glasshouse experiment. As could be expected, both methods indicated that K intensity in soils increased with higher amounts of K dressings and decreased with progressive crop growth. With EUF10, 56–77% of the variation in plant response in dry matter yield and K uptake could be explained, where as with ARo, it was only 36–65%. There was good linear correlation between ARo, and EUF10 for a particular soil; but there was differential variation in the two parameters for the different soils. When compared on the basis of plant response, EUF10 was found to better describe K availability to plants and differentiate better between soils of different K selectivity.