Electro-ultrafiltration Research Articles

Transfer of Phosphate Ions between Soil and Solution: Perspectives in Soil Testing

AbstractPhosphorus inputs must be estimated accurately to optimize the economic return to farmers and minimize P loss from soils to surface waters. Currently, P recommendations are based on the diagnosis of field crop responses by chemically extracted soil P. However, the inability of chemical extraction to characterize plant‐available P limits the reliability of these recommendations. Major sources of P mobilized by plant roots include P ions in solution and those from soil constituents, which replenish and buffer solution. A mechanistic evaluation of soil P supply should therefore be based on the description of P ion transfer between soil constituents and solution. Sorption, desorption, electro‐ultrafiltration (EUF), and isotopic exchange studies show that an adequate modeling of this quantity [Q(CP,t)] of P ions must account for both the concentration of P ions in soil solution (Cp) and time (t). In one long‐term field experiment, the Q(CP,t) description was not affected by crop rotation and mineral fertilization histories; therefore, Q(CP,t) changes are fully explained by CP changes. In two field experiments, CP changes were linearly correlated with the cumulative P budget, inputs, and outputs over years. In three field experiments, the soil type effect on the relative maize (Zea mays L.) response curve was taken into account using the ability of soil P to replenish solution P for 1 d. The residual variance of this diagnosis is halved compared to Olsen's extraction. Although more information is necessary, accuracy is improved when soil testing is based on mobility of P ions.

Characterization of indigenous glauconitic sandstone for its potassium‐supplying potential by chemical, biological, and electroultrafiltration methods

Chemical and biological extraction and electroultrafiltration (EUF) desorption of potassium (K) from four size‐fractions of indigenous glauconitic sandstone were studied to assess its K‐supplying potential. Potassium extracted by chemical extractants showed an increase in K release with decrease in size of the particle. At high acid strength and high temperature and voltage in EUF, the K release was substantially greater, particularly from fine‐sized fractions. About 7 to 9% of the total K in the glauconite was released in 12 consecutive boiling 1M nitric acid (HNO3) extractions. Kinetic studies indicated that the release of K from glauconite was a diffusion‐controlled phenomenon. Pearl‐millet biomass, K concentration in plant tissue, and total K uptake were significantly increased by the addition of fractions of decreasing size. Thus, prospects exist for use of indigenous glauconitic sandstone as a source of K.

RELEASE OF POTASSIUM FROM THE SILT AND SAND FRACTION OF LOESS-DERIVED SOILS

The objective of this investigation was to examine whether the silt in loess-derived soils represents a major K+ source for plants. The experiment was carried out with 14 arable loess-derived soils (Alfisols) from which, in one series, the clay was removed and in which, in another series, complete soils were used. In this work, the latter are denoted as whole soils, whereas the soils without clay are labeled silt + sand fractions, of which the silt proportion was about 80%. Potassium was extracted from whole soils and from silt + sand fractions by electroultrafiltration (EUF). Potassium quantities extracted from the silt + sand fractions were about half the K+ quantities extracted from whole soils. Potassium rates extracted and plotted on extraction time yielded curves that fitted the Elovich equation. Dry matter yield of ryegrass (Lolium perenne) grown in pots on whole soils did not differ significantly from dry matter yields obtained from grass grown in pots on silt + sand fractions. Thus, it is suggested that the K+ present in the silt + sand fraction was readily available to the grass. Close correlations between K+ uptake of the grass and K+ soil parameters were obtained with the EUF extraction at 400 V and 80°C, with which the interlayer K+ was mainly obtained. The b values of the Elovich equation reflect the K+ release rates of interlayer K+. The data provide evidence that in loess-derived soils, the silt fraction, presumably because of its high mica concentration, is of great importance for the supply of K+ to plants.

Effect of the biocontrol agent Pseudomonas fluorescens F113 released as sugarbeet inoculant on the nutrient contents of soil and foliage of a red clover rotation crop

The biocontrol agent Pseudomonas fluorescens F113, which produces the antimicrobial compound 2,4-diacetylphloroglucinol and inhibits soil-borne phytopathogenic fungi, might also affect non-target resident microorganisms involved in the cycling of soil nutrients. Analyses of soil nutrients and crop foliage were used to assess possible residual effects of the pseudomonad on soil fertility. The Bandon field site was sown in 1994 with sugarbeet seeds that were either untreated, inoculated with the spontaneous rifampicin-resistant mutant F113Rif, or treated with chemical fungicides. The field was cropped with uninoculated red clover in 1995. The inoculant was recovered at only 2.0 log CFU/root system at the first harvest of clovers, and the F113Rif treatment influenced 5 of 17 levels of readily available nutrients determined by electro-ultrafiltration (EUF) analysis of soil. However, this effect was essentially negligible since it was (1) small in magnitude and of little agronomic significance when compared with reference EUF levels, (2) similar in part to those of the commercial seed treatment and other farming practices followed at Bandon, and (3) not statistically significant when data were analysed at the plot level rather than using results from individual soil samples within plots. Clover leaf composition was investigated at two harvests. The F113Rif treatment had no effect on the 20 foliage parameters studied except a small (15%) transient decrease in foliage chlorine at the first harvest. EUF soil analysis and foliage analysis will be useful in future risk assessment studies of genetically modified derivatives of F113.

Prediction of mineralizable nitrogen in soils on the basis of an analysis of extractable organic N

AbstractMost of the nitrogen (N) in agricultural soils is organically bound, while the N uptake by plants and also the N losses from the soil‐plant system into the environment are as inorganic N. The electro‐ultrafiltration (EUF) method and the extraction by a CaCl2 solution extract an organic N fraction (Norg) that is thought to provide information about the amount of rapidly mineralizable N in soils. This paper aims to illustrate various aspects regarding the biological meaning of the Norgfractions extracted by these two extraction methods and also the opportunities and limitations for predicting the mineralizable N based on an Norg analysis.From an evaluation of numerous data on EUF and CaCl2 extract‐able Norg fractions we concluded that these methods extract N compounds which can be used as indices for easily mineralizable soil N. However, both methods extract only some of the rapidly mineralizable N in soils, and some of the Norg ecxtracted appears to be from the more recalcitrant soil organic N. This was particularly true for the EUF‐method. It may therefore be desirable to improve both the extractability and the selectivity of the extraction methods. This may be achieved by measuring extractable amino‐N compounds instead of the total extractable Norg.Evaluating the numerous field experiments done during the last decade shows that the calibration factors obtained for extractable Norg were not the same for different growing seasons, geographical regions and management practices. Theoretically, for each combination of these factors separate calibrations would be necessary. It is this inflexibility which appears to be the most serious drawback for the use of extractable Norg fractions in practice.A possible solution may be to combine the flexibility of a simulation model with additional information obtained by the analysis of extract‐able soil organic N. Further work in this direction may be desirable.

Bioavailable tests: alternatives to standard soil extractions

Due to the complexity of the soil plant system and in spite of the enormous amount of information available, the search for better methods to determine the bioavailability of nutrients to plants continues to be important. The large number of methods of soil analysis available worldwide in routine soil testing is an unquestionable demonstration of the lack of agreement on best alternatives. The question discussed in this paper, based on a literature review, is if those methods, considered here as the “standard methods”; of soil analysis, are the best possible alternatives for the evaluation of bioavailability of elements in soil. As alternative non‐standard methods, electroultrafiltration (EUF), the extraction with 0.01 mol calcium chloride (CaCl2 L‐1solution, the extraction with ion‐exchange resin and the adsorption of phosphorus (P) on iron oxide treated paper filter (Pi), were considered. These four methods were compared with the standard methods Olsen, Mehlich 1, Bray 1, Mehlich 3, AB‐DTPA, Egnér, water, ammonium acetate (NH4OAc), and DTPA. The criterion used to compare the different methods was the percent variation (100 r2) associated with the correlations of plant indexes of bioavailability, in most cases uptake by plants, and soil contents of the elements. For P, the extraction with ion‐exchange resin presented considerable higher values of the percent variation, in comparison with the standard methods, EUF, and CaCl2. The resin extraction is adaptable to all types of soils, including acid and alkaline, which is not the case for the standard methods. Comparisons for other elements was impaired by the limited amount of data available, but better alternatives to the standard methods are not yet available. The extraction with resin seems to be feasible for other elements, including potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), nitrogen (N), molybdenum (Mo), copper (Cu), manganese (Mn), zinc (Zn), cadmium (Cd), and lead (Pb), but there is a need for a practical laboratory technique to determine all those elements and the biological validation with plant experiments. Thus only for P is there a more accurate alternative to evaluate bioavalilabity of nutrients in soils.

Soil enzyme activities in the rhizosphere of field-grown sugar beet inoculated with the biocontrol agent Pseudomonas fluorescens F113

Pseudomonas fluorescens F113, which produces the antimicrobial compound 2,4-diacetylphloroglucinol, is a prospective biocontrol agent. Soil enzyme activities were used to investigate the ecological impact of strain F113 in the rhizosphere of field-grown sugar beet. There were distinct trends in rhizosphere enzyme activities in relation to soil chemistry [determined by electro-ultrafiltration (EUF)]. The activities of enzymes from the P cycle (acid phosphatase, alkaline phosphatase and phosphodiesterase) and of arylsulphatase were negatively correlated with the amount of readily available P, whereas urease activity was positively correlated with the latter. Significant correlations between nutrient levels determined by EUF and enzyme activities in the rhizosphere were obtained, highlighting the usefulness of enzyme assays to document variations in soil nutrient cycling. Contrary to previous microcosm studies, which did not investigate plants grown to maturity, the biocontrol inoculant had no effect on enzyme activities or on soil chemistry in the rhizosphere. The results showed the importance of using homogenous soil microcosm systems, also employed in previous work, for risk assessment studies, whereby the effects of inherent soil variability were minimised, and effects of the pseudomonad on soil enzymology could be detected.

Comparing tests for soil fertility. III. Evaluation of phosphate availability in Alfisols by Olsen, Mehlich 3, electro‐ultrafiltration, and the paper‐strip methodology procedures

The suitability of the “iron‐impregnated paper‐strip”; (Pi) methodology for the assessment of phosphate (P) availability in soils has been tested on the basis of a comparison with the classical Olsen method as well as with the new‐generation electro‐ultrafiltration (EUF) and Mehlich No. 3 (M3) extraction procedure. The EUF extractions were performed by a first 30 min run at low (L) energy conditions (20°C, max 15 mA, and 200V), followed by a 10 min run at high (H) energy conditions (80°C, max 150 mA, and 400V). The total EUF‐P extracted (T‐EUF‐P), given by the sum L‐EUF‐P + H‐EUF‐P, was also considered. The investigation was carried out on twenty samples of representative Alfisols ("Terra Rossa") from the pedoclimatic environments of the Mediterranean area. The soil samples were characterized by a large variability of their available‐P values, whose ranges were, as mg‐kg‐1 soil, 0.1–34.0 for L‐EUF‐P, 0.2–39.3 for HEUF‐P, 0.3–73.3 for T‐EUF‐P, 0.8–113.6 for Olsen‐P, 1.0–122.4 for Pi‐P, 1.1–224.6 for M3‐P. The respective mean values were 4.6, 5.1, 9.6, 17.2, 20.1, and 29.7 mg P/kg soil, with ratios L‐EUF‐P:H‐EUF‐P:T‐EUF‐P:Olsen‐P:Pi‐P:M3‐P increasing as 0.27:0.29:0.56: 1.00:1.17:1.73. A good compliance among all methods was verified; the most significant correlations were determined for Pi‐P versus M3‐P (R2=0.993***) and for Pi‐P versus Olsen‐P (R2=0.988***), clearly indicating the liability of the Pi procedure for the assessment of the P fertility in Alfisols. A multiple linear regression analysis revealed that all the available P values, afar from the individual procedure, were significantly (P<0.01) dependent on M3 exchangeable iron (Fe) (positively) and aluminum (Al) (negatively). This could lead one to argue that the prevailing available soil P source in the investigated Alfisol samples was that connected with the labile Fe‐P pool. Withal, one could infer that the A1‐M3 and Fe‐M3 parameters should also be considered for the making of P fertilizer recommendations. From this standpoint, the M3 is a well‐proved multielement extractant suitable for the simultaneous determination of available P and exchangeable Fe and Al as well.

Effect of Applying Soluble and Coated Phosphate Fertilizers on Phosphate Availability in Calcareous Soils and on P Absorption by a Rye-Grass Crop

The effect of using several phosphoric fertilizers on phosphate availability in calcareous soils with a high phosphorus fixation capacity was studied. Tests were run with commercial fertilizers, differing in the ionic species provided (urea phosphate, triple superphosphate, simple superphosphate, and diammonium phosphate), and experimental controlled-release fertilizers (lignin-coated triple superphosphate and rosin-coated diammonium phosphate), each providing phosphate to the soil at a different rate. Simultaneous experiments were run (in calcareous soils) with a plant (glasshouse test) and with no plant (incubation test). Phosphate availability and, therefore, plant phosphorus absorption increased in such soils when fertilizing with urea phosphate (UP) or with lignin-coated triple superphosphate (TSPL-11). Other fertilizers such as uncoated superphosphates or diammonium phosphate (DAP) did not significantly increase P availability compared to the unfertilized soil. The electroultrafiltration (EUF) techn...

Soil nitrogen fractions as influenced by sample preparation and extraction

In order to evaluate the influence of extraction procedure on extractable nitrogen (N) fractions, fresh as well as dried soil samples were extracted with CaCl2 at various temperatures (20,40,60, 80°C) for 30–120 minutes. Data obtained were compared with those from the electro‐ultra‐filtration (EUF) method. Increasing the drying temperature as well as the extraction temperature led to an increase in Norg content. The EUF and CaCl2‐method produced comparable results for all N‐fractions (NO3 ‐, NH4 +, Norg) when an extraction temperature of 80°C was applied for two hours. Data presented suggested that the Norg fraction represented mainly the microbial biomass and may thus be considered as being easily available to plants.

Potassium Status in Maize Rhizosphere of Smectitic Soils

AbstractThis study has been taken up to generate information on potassium status in maize rhizosphere soils differing in their clay content at different levels of added potassium. Soils with larger amounts of clay showed greater amounts of water soluble and ammonium acetate extractable K (NH4OAc K) in both the rhizosphere as well as non‐rhizosphere. In the absence of added K (control), non‐rhizosphere samples showed higher water soluble and NH4OAc K ranging from 8.0 to 28.9 mg kg−1 and from 132.5 to 294.0 mg kg−1, respectively compared to rhizosphere samples where water soluble K varied between 6.0 and 26.5 mg kg−1 and NH4OAc K from 125.0 to 262.5 mg kg−1. The difference in K content between rhizosphere and non‐rhizosphere which could have been resulted from plant K uptake was significantly related with clay content (r = 0.98**) in control whereas at 150 mg kg−1 K addition this relationship was found to be non significant (r = 0.64NS). Electro ultra filtration (EUF) fractions also showed similar differences in K contents in soil between rhizosphere and non‐rhizosphere.

Extractability of labelled microbial biomass N by electro-ultrafiltration and CaCl2 extraction

A laboratory soil incubation and a pot experiment with ryegrass were carried out in order to examine the extractability of microbial biomass N by using either 10-mM CaCl2 extraction or the electro-ultrafiltration (EUF) method. The aim of the experiment was to test the hypothesis whether the organic N (Norg) extracted by EUF or CaCl2 from dried soil samples represents a part of the microbial biomass. For the laboratory incubation a 15N-labelled Escherichia coli suspension was mixed with the soil. For the pot experiment a suspension of 15N-labelled bacteria was applied which had previously been isolated from the soil used. Soil samples of both treatments, with and without applied bacterial suspension, were extracted by EUF and CaCl2. The extractability of applied microbial biomass was estimated from the difference in extractable Norg between the two treatments. In addition, the N isotopic composition in the upper plant matter, in the soil, and in organic and inorganic N fractions of EUF and CaCl2 extracts was analysed. Both experiments showed that the applied microbial biomass was highly accessible to mineralization and thus represented potentially mineralizable N. However, this mineralizable N was not extractable by CaCl2 or by the EUF method. It was, therefore, concluded that the organic N released on soil drying and which was thus extractable was derived from the non-biomass soil organic matter. The result suggests that both extraction methods may provide a suitable index for mineralizable N only in cases where the decomposable organic substrates are derived mainly from sources other than the living soil biota.

Influence of organic compounds on nitrogen‐fertilizer solubilization

Abstract In the attempt to find new products which release nutrients in gradual forms, the behavior of two commercial fertilizers was studied, Nitrophoska® (N) and urea (U), covered with two organic materials, humic acid (HA) and alginic acid (AA). The release of nitrogen from the fertilizers was determined by electroultrafiltration (EUF). These applied materials on the fertilizer surface resulted in a slowing of the release of nitrogen, although strictly speaking, these compounds do not function as coated fertilizers. Their effectiveness depends on the fertilizer, for with Nitrophoska®, the addition of alginic acid was more effective, while for urea, the addition of humic acid slowed the release of nitrogen.

Determination of K forms in K-fertilized soils by electro-ultrafiltration

We confirmed the suitability of electro-ultrafiltration (EUF) for (a) determination of the distribution of potassium fertilizer among the various forms of potassium in soils with a predominance of micaceous minerals in their clay fraction, and (b) investigated the effects of the degree of openness of the dominant micaceous mineral and of incubation time on the kinetics of the EUF extraction of K from these soils.

Determination of available phosphorus in soils from northern Greece by the electro‐ultrafiltration (EUF) and other methods of soil analysis

Abstract The suitability of electro‐ultrafiltration (EUF) and other methods of soil analysis, commonly practised worldwide, for the assessment of available phosphorus (P) in 21 soils taken from various locations of northern Greece, as defined by P uptake and dry matter yield of ryegrass grown in pots, was studied. Significant correlations were found to exist between the quantities of P uptake by ryegrass and those of P extracted by the various methods. Phosphorus uptake by ryegrass correlated best with the P‐resin contents (r = 0.91***), while the poorest correlation was observed with the organic P fraction (r = 0.53*). The correlation between EUF‐P at 20°C and P uptake by ryegrass was highly significant (r = 0.84***) and became even higher when the values of the quotient EUF‐P 80°C/EUF‐P 20'C, i.e. the P reserves, were taken into account. Of all the methods tested, the Olsen‐P method proved least sensitive to changes in pH, texture, cation exchange capacity (CEC), and percent base saturation.

Electro-ultrafiltration bioreactor for enzymatic reaction in reversed micelles

Electro-ultrafiltration (EUF), which is an effective method to decrease gel layer formation in membrane surface and to increase the flux of filtrate, was used in the membrane bioreactor for lipase-catalyzed hydrolysis of triolein in a reversed micellar system. An ultrafiltration ceramic membrane module of tubular type was used to separate the AOT (bis(2-ethylhexyl) sodium sulfosuccinate, Aerosol OT) reversed micelles containing lipase and product from the continuous phase of isooctane. The effects of an electric field, W o (molar ratio of water to surfactant) and AOT concentration on the filtration flux and the stability of lipase activity were studied. For the EUF bioreactor, optimum conditions of the reversed micelles with respect to the filtration flux and the stability of lipase activity were obtained as W o = 3 and 0.02 M AOT. The application of an electric field improved the productivity of oleic acid, because the filtration flux increased with increased electric field strength. The EUF bioreactor could be effectively operated in the continuous enzymatic reaction of the reversed micellar system, because the enzyme-containing reversed micelles were retained in a continuously operated reactor and the product solution was removed from the reactor.

Evaluation of euf‐potassium quotient as a measure of potassium buffering capacity of illite‐dominant soils under intensive cropping

Abstract Suitability of the electro‐ultrafiltration (EUF)‐potassium (K) quotient, a ratio between strongly held and easily desorbable EUF fractions of K to measure K‐buffering capacity of illite‐dominant soils under intensive cropping, was studied. EUF‐K quotients which ranged from 0.333 to 0.580 before cropping increased to the range of 0.405 to 0.710 after the cropping. As a result of cropping, the mean K‐ replenishment rate decreased from 6.98 kg/ha/day to 0.2 kg/ha/day, whereas the mean EUF‐K quotient increased from 0.43 to 0.53. EUF‐K quotient showed significant positive correlation with dry matter yield (r = 0.78*) and K uptake (r = 0.79*) in the first harvest of crop and in the subsequent harvests it maintained correlations of lower order. While other EUK‐K fractions, i.e. EUF 20°C, EUF 80°C, and EUF 35 min increased or maintained the same extent of correlation with conventional soil test methods after cropping, EUF‐K quotient failed to have significant correlation with those soil test methods afte...

Phosphorus Release Kinetics and Extractable Phosphorus after Long‐term Fertilization

AbstractIf different P fertilizers have been applied for a long time, it is difficult to measure the P availability. The objectives of this study were to investigate (i) the kinetics of soil P release by electroultrafiltration (EUF), (ii) extractable P using different soil extractants, (iii) plant P uptake, and (iv) the importance of considering both the P release kinetics and extractable P for plant P uptake prediction. This study was conducted with 15 European Alfisol topsoils with different histories of P and lime applications. The soils had received P as basic slag phosphate (BSP), superphosphate (SP), partially acidulated phosphate rock (PAPR), and phosphate rock (PR) for a long period. Plant P availability was measured in a 4‐yr pot experiment with different plants. Phosphorus release kinetics analyzed by EUF were better described by the Elovich equation than by other diffusion functions. The Elovich b values, which can be used as an index of release rate, ranged from 53.5 to 140.0 mg P kg−1 soil min−1. These b values were more closely correlated to cumulative plant P uptake (r = 0.96) than P extracted with water (r = 0.90), calcium acetate‐calcium lactate‐acetic acid (CAL) (r = 0.89), Mehlich 3 (r = 0.81), and double lactate (r = 0.79). Only Elovich b values in the PAPR and PR treatments were significantly correlated to cumulative plant P uptake (r = 0.92). The cumulative plant P uptake of the 15 soils was well predicted with the fitted equation: y = 27.8 + (0.40 CAL P) + (0.83b), r = 0.99, where y denotes the plant P uptake and b is the Elovich b value (mg P kg−1 soil min−1) and CAL P is the adsorbed P. This indicates that considering the b value as a parameter for P release and the amount of CAL‐extractable P for determining P availability following different fertilizer applications is a better estimation of plant P uptake than consideration of only one index of P availability.

Bioavailability and distribution of phosphorus among inorganic fractions in calcareous soils

Deficiency of phosphorus (P) is widespread in calcareous soils. Phosphorus uptake by plants responding to P application on such soils generally shows poor correlation with their soil test P values. Experiments were conducted under laboratory and greenhouse conditions to elucidate the relationship of various inorganic P fractions in eleven calcareous soils with P uptake by plants, P extraction by electro‐ultrafiltration (EUF), and P extraction by other commonly used methods. Total P ranged from 92.5 to 862.5 mg P kg‐1 soil. A major proportion (88–99%) of inorganic P was in HCl‐P (Ca bound) form. Phosphorus extraction by EUF followed the power function equation. The intercept values calculated ranged from 0.13 to 0.94 mg P kg‐1 soil. The NaOH‐P (nonoccluded Fe and Al‐bound P) and CB‐P (citrate‐bicarbonate extractable P) together explained 76% variation in the intercept values. The slope (rate constant) correlated (r = 0.58) with the HCl‐P (Ca bound) form. Application of 90 mg P kg‐1 soil significantly (P < ...

Determination of Atrazine Residues in Electro‐Ultrafiltration Soil Extracts by a Sensitive Enzyme Immunoassay

AbstractA sensitive enzyme immunoassay (EIA) based on polyclonal antibodies from sheep was used to screen for atrazine in electro‐ultrafiltration (EUF) soil extracts without clean‐up. Matrix effects were circumvented by diluting the aqueous EUF extracts. The EUF proved to be a convenient method for the extraction of atrazine residues in soil. The efficiency of EUF appeared to be equivalent to that of organic extraction methods except on weathered residues, which generally resulted in lower yields. Both the combined gas chromatography/automated Soxhlet (GC/Soxtec) and the immunochemical technique EIA/EUF yielded similar data for the 26 soil samples identified as positive (&gt; 0.02 mg/kg) during the first screening of 479 EUF extracts by the EIA.