Glyphosate bioavailability in soil

Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction. The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth; 6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3.     

Plantago lanceolata L. and Rumex acetosella L. differ in their utilisation of soil phosphorus fractions

To establish relationships between soil phosphorus (P) fractions and leaf P, a mycorrhizal species (Plantago lanceolata L.) was compared with a typically non-mycorrhizal species (Rumex acetosella L.) in a glasshouse experiment. The plants were grown in 40 soils from non-fertilised, abandoned pastures or abandoned arable fields and leaf P concentration were found to be related to various soil P fractions after six weeks of growth. The differences in the P fractions in soil can account for a large share of the variation in leaf P concentration in both species, but the two species differed in their utilisation of P fractions. Leaf P concentration of R. acetosella was more related to extractable soil P than that of P. lanceolata. Rumex acetosella showed a higher maximum P concentration. The P fractions accounting for the largest share of the variation in leaf P concentration was the Bray 1 extractable and the weak oxalate (1 mM) extractable P, and for P. lanceolata also the Na₂SO₄+NaF extractable P fraction. P extracted with these methods accounted for up to 80% of the variation in P concentration in leaves of R. acetosella and 65% of the variation in leaves of P. lanceolata. More P extractable with weak oxalate, Na₂SO₄+NaF and strong oxalate (50 mM) was released from the soil than was taken up by the plants during the experimental period. The Bray 1 extractable P fraction, however, decreased in both unplanted and planted soils. Phosphatase release was not induced in any of the plants during the experimental period, indicating that they were not mobilising soil organic P. However, some of the methods extracted a large share of the organic P and still explained much of the variation in leaf P concentration. Mycorrhizal colonisation of P. lanceolata was inversely related to the extractable soil P. The consistently fast P uptake of R. acetosella indicates that this species have a high demand for P. The differences in P utilisation between R. acetosella and P. lanceolata could be caused by their different mycorrhizal status.     

Using Soil Available P and Activities of Soil Dehydrogenase and Phosphatase as Indicators for Biodegradation of Organophosphorus Pesticide Methamidophos and Glyphosate

The heavy use of organophosphorus pesticides in northeastern China strongly affects the ecological functions and the quality of the soil environment. In this work, a 30-day soil incubation experiment was conducted to evaluate the potential of using soil available P and the activities of soil dehydrogenase and acid phosphatase as indicators of the application of methamidophos and glyphosate. Two kinds of unpolluted soils, phaiozem and burozem, were selected as the test soils. The higher application rate of organophosphorus pesticide to the two soils caused more release of PO₄ ^3? which finally entered the soil available P pool, suggesting that soil available P is one of the effective chemical markers for biodegradation of organophosphorus pesticides. Methamidophos exhibited a significant inhibitory effect on the activity of soil dehydrogenase. The extent of enzyme inhibition was almost positively correlated with the insecticide concentration, and the enzyme activity was gradually restored after day 15. However, its effect on soil acid phosphatase activity (stimulation or inhibition) seemed to be indefinite, and varied with the application rate, soil type, and incubation time. In the case of glyphosate, soil acid phosphatase activity was depressed significantly and the depressing extent could be a function of herbicide concentration and incubation time, but soil dehydrogenase activity showed an irregular variation with the herbicide application rate and soil type. In general, dehydrogenase activity was a good biochemical indicator for the biodegradation of methamidophos, but for glyphosate biodegradation the indicator was acid phosphatase activity.     

Effect of glyphosate on the microbial activity of two Romanian soils

Glyphosate applied to soils potentially affect microbial activity. A series of field and laboratory experiments assessed the effect of this herbicide on soil microorganisms. The aim of experiments was to evaluate the effect of glyphosate application on the soil microbial community structure, function and their activity. We studied "in vitro", changes in the microbial activity of typical Chernozem and Gleysol soils, with and without applied glyphosate. The herbicide was applied at a rate of 2, respectively 4 mg kg(-1) of soil and microbial activity were measured by fluorescein diacetate (FDA) hydrolysis. We found an increase of 9 to 13% in FDA hydrolyses in the presence of glyphosate in rate of 2 mg kg (-1) compared with the same type of soil which had never received herbicide. The double quantity of glyphosate decrease soil microbial activity; the amount of hydrolyzed fluorescein is lower than the addition of 2 ppm. The greater decrease was observed in the Gleysol type where the fluorescein hydrolyzed is with 4, 85% lower than version control without glyphosate. Chemical characters of soil, influence soil biological activity when herbicide is added. In Chemozem case, rich in humus, whose predominant micro flora is represented by actinomycetes through glyphosate treatment these organisms growths of as major producers of antibiotics actinomycetes determine an inhibitory effect on eubacteria and micromycetes growth, which is highlighted by estimating a relatively small number of them. After 10 days, once with decreasing of glyphosate content in soil, decreases the number of active actinomycetes, therefore we are witnessing to a numerical growth of bacterial population. In Gleysol type the indigenous micro flora is represented by eubacteria, so when the glyphosate is added it was registered a high growth of these organisms fraction.     

Selection of Glyphosate-Tolerant Tobacco Calli and the Expression of this Tolerance in Regenerated Plants

From nonmutagenized haploid suspensions of Nicotiana tabacum L. cv Wisconsin 38 cells, 51 cell lines capable of growth in the presence of 1 millimolar glyphosate (N-phosphonomethyl glycine) were initially isolated at a frequency of 2.3 × 10⁻⁸. Eighteen cell lines retained tolerance when grown on selective medium for 3 years. Tolerance persisted for at least 14 months in six cell lines cultured in the absence of glyphosate. Some plants regenerated from four glyphosate-tolerant cell lines were tolerant. Glyphosate-tolerant tissue was isolated from some sensitive as well as some tolerant regenerated plants. Six of the tolerant cell lines were also tolerant to the herbicide amitrole (3-amino-1,2,4-triazole). Five cell lines selected for amitrole tolerance were glyphosate tolerant. Some plants regenerated from three of these five cell lines were glyphosate tolerant and glyphosate-tolerant tissue was obtained from several of these regenerated plants. Amitrole uptake in suspension cultures of several variants was assessed in terms of influx rate constants. This parameter was not sufficiently different indicating that altered membrane properties could not account for the herbicide tolerance.     

Complex Interaction and Adsorption of Glyphosate and Lead in Soil

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide widely used in large quantities in agricultural applications. It is also known to form complexes with metal ions, although its influence on metal behavior, such as lead (Pb) in soil, is not well understood. In this study, the adsorption and co-adsorption of Pb and glyphosate were determined on two soils [a red (RS) soil, Udic Ferrisol, and a yellow-brown (YB) soil, Udic Luvisol] of distinctly different chemical characteristics at varying pH conditions. Results indicate that the adsorption of lead and glyphosate strongly depends on soil types: the RS soil, characterized by a relatively high iron/aluminum content but a low pH and organic matter content, shows a much lower adsorption capacity for Pb but a higher sorption for glyphosate than the YB soil. The co-existence of Pb and glyphosate in soils resulted in complex interactions among Pb, glyphosate, Pb-glyphosate complexes, and soil minerals. The presence of glyphosate decreased Pb adsorption on the two soils, which was attributed primarily to the formation of soluble Pb-glyphosate complexes having relatively low affinities to soil surfaces. On the other hand, addition of Pb increased the adsorption of glyphosate on both soils, which was attributed to: (1) a decreased solution pH due to the ion exchange between Pb²⁺ and H⁺ on soil surfaces; and (2) increased sorption sites where Pb was adsorbed and acted as a bridge between glyphosate and the soil. The present study illustrates that the complex interactions among glyphosate, Pb, and soil may have important implications for the mobility and bioavailability of Pb in soil and should thus be considered in future environmental risk assessments.     

佛山地区存留自然林和存留人工林的土壤无机磷组分

为探讨热带亚热带森林,尤其城市及其周边地区残存森林土壤磷的有效性,对佛山地区14个残存林(7个自然林和7个人工林)的0~3 cm和3~23 cm矿质土壤的P有效性进行研究。结果表明,铁结合态无机P和还原剂可溶解无机P是土壤无机P的主要组分。在0~3 cm矿质层中,自然林土壤铝结合态无机P、Bray 1提取无机P和总无机P含量显著高于人工林;而在3~23 cm矿质土层中,自然林土壤钙结合态无机P含量显著高于人工林。其它土壤营养指标在自然林和人工林间差异不显著。相关分析结果表明,土壤有机质含量与钙结合态无机P除外的其它无机P组分含量均成显著正相关。聚类分析结果表明14个残存林土壤P有效性可分成3组,整体上人工林土壤P有效性比自然林低。这有助于认识城市化影响下城市及其周边地区残存森林土壤营养状况及加强养分管理。     

Phytotoxicity of glyphosate soil residues re-mobilised by phosphate fertilisation

It has been repeatedly demonstrated that phosphate (P) and the herbicide glyphosate compete for adsorption sites in soils. Surprisingly, the potential consequences of these interactions for plants e.g. re-solubilisation of phytotoxic glyphosate residues in soils by application of P fertilisers or by root-induced mechanisms for P mobilization have not been investigated so far. In model experiments under greenhouse conditions, the potential for glyphosate re-mobilisation by P-fertiliser application was evaluated by bio-indication with soybean (Glycine max L.) cultivated on five contrasting soils with or without glyphosate application at 10?C35 days before sowing. Different levels of P-fertilisation (0, 20, 40, 80, 240 mg P kg^?1 soil) were supplied at the date of sowing. Visual symptoms of glyphosate toxicity, plant biomass, intracellular shikimate accumulation as physiological indicator for glyphosate toxicity and the plant nutritional status were determined. On glyphosate-treated soils, P application induced significant plant damage. Expression of damage symptoms declined in the order Arenosol > Acrisol ?? Ferralsol > Luvisol subsoil > Regosol. On the Arenosol, Ferralsol and Luvisol subsoil plant damage was associated with increased shikimate accumulation in the root tissue. On the Acrisol decline of germination and plant damage in absence of shikimate accumulation indicate toxicity of AMPA (aminomethylphosphonic acid) as the main metabolite of glyphosate in soils. On the Regosol, a growth-stimulating effect of glyphosate soil application (hormesis) was detected. The results suggest that re-mobilisation of glyphosate may represent an additional transfer pathway for glyphosate to non-target plants which is strongly influenced by soil characteristics such as P fixation potential, content of plant-available iron, pH, cation exchange capacity, sand content and soil organic matter.     

Glyphosate selected amplification of the 5-enolpyruvylshikimate-3-phosphate synthase gene in cultured carrot cells

Summary CAR and C1, two carrot (Daucus carota L.) suspension cultures of different genotypes, were subjected to stepwise selection for tolerance to the herbicide glyphosate [(N-phosphonomethyl)glycine]. The specific activity of the target enzyme, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), as well as the mRNA level and copy number of the structural gene increased with each glyphosate selection step. Therefore, the tolerance to glyphosate is due to stepwise amplification of the EPSPS genes. During the amplification process, DNA rearrangement did not occur within the EPSPS gene of the CAR cell line but did occur during the selection step from 28 to 35 mM glyphosate for the C1 cell line, as determined by Southern hybridization of selected cell DNA following EcoRI restriction endonuclease digestion. Two cell lines derived from a previously selected glyphosate-tolerant cell line (PR), which also had undergone EPSPS gene amplification but have been maintained in glyphosate-free medium for 2 and 5 years, have lost 36 and 100% of the increased EPSPS activity, respectively. Southern blot analysis of these lines confirms that the amplified DNA is relatively stable in the absence of selection. These studies demonstrate that stepwise selection for glyphosate resistance reproducibly produces stepwise amplification of the EPSPS genes. The relative stability of this amplification indicates that the amplified genes are not extrachromosomal.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - DTT dithiothreitol - EPSPS 5-enolpyruvylshikimate-3-phosphate synthase - I₅₀ 50% inhibitory concentration - Kb Kilobase (pairs) - PEP phosphoenolpyruvate - PMSF phenylmethylsulfonyl fluoride - PVPP polyvinylpolypyrrolidone - S-3-P shikimate-3-phosphate     

Glyphosate tolerance and utilization by the microflora of soils treated with the herbicide

Summary The effect of recurrent applications of the herbicide glyphosate on a garden soil was investigated. Compared to an adjacent untreated soil the microbial population showed reduced sensitivity to glyphosate when grown in mineral salts medium. In both populations inhibition could be partially reversed by addition to the medium of the end products of the aromatic amino acid biosynthetic pathway, but the effect was more pronounced in the population from the treated site. However, all isolates from both soils were capable of growth in unsupplemented medium in the presence of as much as 10 mM glyphosate. No evidence for glyphosate metabolism was obtained from enrichment experiments carried out using inocula from the untreated soil; at the treated site organisms capable of using glyphosate as sole C or N source could not be isolated but a variety of Gram-negative bacteria able to use its phosphonate moiety were obtained. Many of these organisms were identified as Pseudomonas spp.     

Vegetation effects on phosphorus fractions in set-aside soils

As increasing amounts of arable land are being set aside, it is of importance to study the effect of vegetation on soil fertility. The fractionation of soil P under grassland, beech and spruce vegetation was investigated in sites previously fertilized with P by extracting sequentially with Resin, NaHCO₃, NaOH, HCl and finally NaOH after ultrasonic pretreatment. Under beech a large part of extractable P was found in inorganic fractions which are considered to be available for plants (Resin P₁ and Bicarbonate P₁). Under grass, a large part of the extractable P was found in potentially labile organic forms (Bicarbonate P_o and Fulvic acid P_o). After 25 years of permanent grass vegetation, the extractability of soil P was comparable to that from an adjacent arable plot. On spruce covered soils most of the added fertilizer P was rendered unextractable 20–30 years after application. However the available data does not allow a clear interpretation of this phenomena, as effects of soil parent material as well as vegetation may be taken into consideration. No decrease in P-extractability was found between beech and grass covered soils which had been fertilized for more than 200 years, when compared to less rich soils from the same area. On the basis of the current data it may be concluded that the vegetation affects the distribution of soil phosphorus fractions, and thus soil fertility. In the soils under investigation, grassland and beech vegetation conserved the phosphate availability to a high extent.     

Persistence of tree related patterns in soil nutrients following slash-and-burn disturbance in the tropics

Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO₃ ^-), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO₃ ^-, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impact of Atmospheric Nitrogen Deposition on Carbon Dynamics in Two Scots Pine Forest Soils of Northern Germany

The impact of atmospheric N deposition on the dynamics of various carbon fractions was investigated in two Scots pine forest soils (cambisol, podzol) of Northern Germany in microcosm experiments. Total organic carbon (TOC), CO₂ emission, microbial carbon (C_mic) as well as organic hot- and coldwater extractable carbon fractions (C_hwe, C_cwe) were analyzed before, during, and after soil incubation in microcosms, run in three treatments: 0, +45, and +90 kg N ha⁻¹a⁻¹. On both sites, the N treatment showed no response to total organic carbon (TOC) contents in most of the investigated soil layers. Microbial carbon (C_mic) was significantly increased in the organic layer of both soil types by the N application. Subsequent to the N application, the CO₂ emission increased in all mineral soil layers of the cambisol but remained almost unaffected in the podzol. After the N application, a remarkable increase of hotwater extractable C (C_hwe) was detected for the organic layer of the cambisol but not for the podzol, whereas coldwater extractable C (C_cwe) concentrations decreased at both sites. The N application did not have a significant impact on the leachate concentrations of total organic carbon (TOC), dissolved organic carbon (DOC), and particulate organic carbon (POC) in the podzol, whereas the concentrations of these C fractions were decreased in the organic layer and the 35–70~cm mineral soil layer of the cambisol. The N treatment changed the contents of most of the investigated C fractions in both soil types and resulted in a considerable C~mobilization. But the processes of the C~mobilization between the cambisol and the podzol were completely different. According to the presented data, the cambisol obtaining moderate atmospheric N loads is much more sensitive to additional N inputs than the podzol that already received high amounts of atmospheric N.     

Chemical speciation of Zn in acidic soils: suitable soil extractant for assessing Zn availability to maize (Zea mays L.)

Abstract

Chemical fractions of soil Zn namely: water soluble (WS), exchangeable (EX), Pb displaceable (Pb-disp.), acid soluble (AS), Mn oxide occluded (MnOX), organically bound (OB), amorphous Fe oxide occluded (AFeOX), crystalline Fe oxide occluded (CFeOX), residual (RES) were determined in 20 surface (0–15 cm) samples of acidic soils from the provinces of Uttarakhand and Uttar Pradesh, India. The chemical fractions of soil Zn in acidic soils were found to be in the following descending order of Zn concentration: RES > CFeOX > Pb-Disp. > AFeOX > MnOX > AS > OB > EX > WS. These soil samples were also extracted by: DTPA (pH 7.3), DTPA (pH 5.3), AB-DTPA (pH 7.6), Mehlich 3 (pH 2.0), Modified Olsen, 0.01 N CaCl₂, 1 M MgCl ₂ and ion exchange resins. Chemical fractions and the soil extractable content of Zn estimated by different soil extractants were significantly correlated with some general soil properties. Maize (cv. Pragati) plants were grown in these soils for 35 days after emergence and Zn uptake by plants was compared with the amount of Zn extracted by different soil extractants and chemical fractions of Zn. Among chemical fractions of soil Zn, Pb-displaceable and acid soluble chemical fractions of soil Zn showed a significant and positive correlation with Zn uptake by maize. Path coefficient analysis also revealed that the acid soluble Zn fraction showed the highest positive and direct effect on Zn uptake (P=0.960). Among different multinutrient soil extractants evaluated for their suitability to assess Zn availability in acidic soils, DTPA (pH=5.3) was most suitable soil extractant, as the quantity of soil Zn extracted by this extractant showed a significant and positive correlation with the dry matter yield, Zn concentration and uptake by maize plants.     

Effect of some biological factors on soil variability in the tropics

Summary Observations of a selected area in the forest zone of south western Nigeria indicate that the distribution ofMacrotermes bellicosus (Smeathman) andMacrotermes subhyalinus (Rambur) mounds are mainly affected by the drainage conditions of the soils along a toposequence. Higher number of mounds are observed on the better drained soils, ranging from 35.4 to 17.2 mounds/ha covering an area of respectively 0.84 and 0.10 per cent. The shallow and poorly drained soils show lower mound density (<1 mound/ha). The mound soil bears close resemblance to the subsoil, has higher clay content, lower pH, organic C, CEC and extractable P, but higher P retentio than the adjacent surface soil. Growth of maize (Zea mays L.) and soybean (Glycine max. (L.) Merrill) was poorer in the mound soil than in the surface soil. The problem of increased soil variability when large number of mounds are encountered in the field is discussed.     

Development and Application of a Liquid Preparation with Oil-Oxidizing Bacteria

An association of four bacterial strains with high oil-oxidizing and bioemulsifying activities, psychrophilicity, resistance to chemical pollutants, and lack of pathogenicity was selected from a collection of natural oil-oxidizing microorganisms. A new liquid preparation containing stabilizers and preservatives that maintain cell viability and oil-oxidizing activity during long-term storage was developed. A field experiment in oil-polluted sod-podzol and clay sand soils demonstrated that this preparation accelerated the biodegradation of oil and its individual fractions, especially in the presence of mineral and organic fertilizers. Treatment of oil-polluted soil with this preparation and additives decreased the oil-induced suppression of certain groups of soil microflora.     

Biogeochemical implications of labile phosphorus in forest soils determined by the Hedley fractionation procedure

Forest ecologists and biogeochemists have used a variety of extraction techniques to assess labile vs. non-labile soil P pools in chronosequences, the balance between biological vs. geochemical control of P transformations across a wide range of soil orders, the role of plants with either N-fixing or mycorrhizal symbionts in controlling soil P fractions, and to make inferences about plant-available P. Currently, variants of the sequential extraction procedure developed by M. J. Hedley and co-workers afford the greatest discrimination among labile and non-labile organic and inorganic P pools. Results of recent studies that used this technique to evaluate P fractions in forest soils indicate the following: (1) in intact, highly weathered forest soils of the humid tropics, Hedley-labile P values are several times larger than extractable P values resulting from mildly acidic extracting solutions which were commonly used in the past 2 decades; (2) pools of Hedley-labile P are several times larger than the annual forest P requirement and P required from the soil annually in both temperate and tropical forests; (3) long-term trends in non-labile P pools during pedogenesis are adequately represented by the Walker and Syers' model of changes in P fractionation during soil development. However, to better represent trends in pools that can supply plant-available P across forest soils of different age and weathering status, the paradigm should be modified; and (4) across a wide range of tropical and temperate forest soils, organic matter content is an important determinant of Hedley-labile P.     

Creation and use of a liquid substance based on association of petroleum-oxidizing bacteria

An association of four bacterial strains with high oil-oxidizing and bioemulsifying activities, psychrophilicity, resistance to chemical pollutants, and lack of pathogenicity was selected from a collection of natural oil-oxidizing microorganisms. A new liquid preparation containing stabilizers and preservatives that maintain the cell viability and oil-oxidizing activity during long-term storage was developed. A field experiment in oil-polluted sod-podzol and clay sand soils demonstrated that this preparation accelerated the biodegradation of oil and its individual fractions, especially in the presence of mineral and organic fertilizers. Treatment of oil-polluted soil with this preparation and additives decreased the oil-induced suppression of certain groups of soil microflora.     

Bioremediation of glyphosate-contaminated soils

Based on the results of laboratory and field experiments, we performed a comprehensive assessment of the bioremediation efficiency of glyphosate-contaminated soddy-podzol soil. The selected bacterial strains Achromobacter sp. Kg 16 (VKM B-2534D) and Ochrobactrum anthropi GPK 3 (VKM B-2554D) were used for the aerobic degradation of glyphosate. They demonstrated high viability in soil with the tenfold higher content of glyphosate than the recommended dose for the single in situ treatment of weeds. The strains provided a two- to threefold higher rate of glyphosate degradation as compared to indigenous soil microbial community. Within 1–2 weeks after the strain introduction, the glyphosate content of the treated soil decreased and integral toxicity and phytotoxicity diminished to values of non-contaminated soil. The decrease in the glyphosate content restored soil biological activity, as is evident from a more than twofold increase in the dehydrogenase activity of indigenous soil microorganisms and their biomass (1.2-fold and 1.6-fold for saprotrophic bacteria and fungi, respectively). The glyphosate-degrading strains used in this study are not pathogenic for mammals and do not exhibit integral toxicity and phytotoxicity. Therefore, these strains are suitable for the efficient, ecologically safe, and rapid bioremediation of glyphosate-contaminated soils.     

Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane

Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes. Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL deionized water were equilibrated with 5 cm² Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl₂, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested. It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils.