Use Of Soil Amendments Research Articles

The potential of foliar treatments for enhanced phytoextraction of heavy metals from contaminated soil

AbstractPhytoextraction is the plant‐based removal of inorganic contaminants from the soil by root absorption and subsequent translocation to harvestable plant parts. The efficiency of this technique is limited by the phytoavailability of these contaminants in the soil and the root‐to‐shoot transport. To enhance the phytoextraction efficiency, the use of soil amendments has been widely investigated. Potential risks such as increased ecotoxicological effects and leaching of mobilized contaminants caution against the use of persistent mobilizing agents. The potential use of foliar amendments to enhance mineral absorption and/or translocation offers prospects for complementing or substituting soil amendments for enhanced phytoextraction purposes. This study presents an explorative screening to evaluate the feasibility of this approach. Helianthus annuus giganteus plants were grown in moderately contaminated dredged sediment for ten weeks, with daily foliar treatments from week six onward: (1) distilled water (control), (2) magnesium‐ethylenediaminetetraacetic acid (Mg‐EDTA), (3) diethylenetriaminepentaacetic acid (DTPA), (4) nitrilotriacetic acid (NTA), (5) citric acid, (6) oxalic acid, (7) calcium acetate, (8) ammonium thiocyanate (NH4SCN), and (9) cystein. Applied doses varied between treatments based on plant tolerance: 15 μmol per plant for cystein, 60 μmol per plant for DTPA and NH4SCN, 180 μmol per plant for Mg‐EDTA and NTA and 400 μmol per plant for the organic acids. At the end of the experiment, shoot accumulation of cadmium, chromium, copper, iron, manganese, nickel, lead, and zinc was evaluated. © 2004 Wiley Periodicals, Inc.

Enhanced Phytoextraction: In Search of EDTA Alternatives

ABSTRACT Enhanced phytoextraction proposes the use of soil amendments to increase the heavy-metal content of above-ground harvestable plant tissues. This study compares the effect of synthetic aminopolycarboxylic acids [ethylenediamine tetraacetatic acid (EDTA), nitriloacetic acid (NTA), and diethylenetriamine pentaacetic acid (DTPA)] with a number of biodegradable, low-molecular weight, organic acids (citric acid, ascorbic acid, oxalic acid, salicylic acid, and NH4 acetate) as potential soil amendments for enhancing phytoextraction of heavy metals (Cu, Zn, Cd, Pb, and Ni) by Zea mays. The treatments in this study were applied at a dose of 2 mmol/kg−1 1 d before sowing. To compare possible effects between presow and postgermination treatments, a second smaller experiment was conducted in which EDTA, citric acid, and NH4 acetate were added 10 d after germination as opposed to 1 d before sowing. The soil used in this screening was a moderately contaminated topsoil derived from a dredged sediment disposal site. This site has been in an oxidized state for more than 8 years before being used in this research. The high carbonate, high organic matter, and high clay content characteristic to this type of sediment are thought to suppress heavy-metal phytoavailability. Both EDTA and DTPA resulted in increased levels of heavy metals in the above-ground biomass. However, the observed increases in uptake were not as large as reported in the literature. Neither the NTA nor organic acid treatments had any significant effect on uptake when applied prior to sowing. This was attributed to the rapid mineralization of these substances and the relatively low doses applied. The generally low extraction observed in this experiment restricts the use of phytoextraction as an effective remediation alternative under the current conditions, with regard to amendments used, applied dose (2 mmol/kg−1 soil), application time (presow), plant species (Zea mays), and sediment (calcareous clayey soil) under study.

The use of plants for remediation of metal-contaminated soils.

The use of green plants to remove, contain, inactivate, or degrade harmful environmental contaminants (generally termed phytoremediation) is an emerging technology. In this paper, an overview is given of existing information concerning the use of plants for the remediation of metal-contaminated soils. Both site decontamination (phytoextraction) and stabilization techniques (phytostabilization) are described. In addition to the plant itself, the use of soil amendments for mobilization (in case of phytoextraction) and immobilization (in case of phytostabilization) is discussed. Also, the economical impacts of changed land-use, eventual valorization of biomass, and cost-benefit aspects of phytoremediation are treated. In spite of the growing public and commercial interest and success, more fundamental research is needed still to better exploit the metabolic diversity of the plants themselves, but also to better understand the complex interactions between metals, soil, plant roots, and micro-organisms (bacteria and mycorrhiza) in the rhizosphere. Further, more demonstration experiments are needed to measure the underlying economics, for publicacceptance and last but not least, to convince policy makers.

Lability of Cd, Cu, and Zn in polluted soils treated with lime, beringite, and red mud and identification of a non-labile colloidal fraction of metals using istopic techniques.

The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 microm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool of metals increased sharply and in the case of lime and beringite, the lability of the metals was similar, at equal pH, to the untreated soil. In contrast the lability of metals in the red mud treated soils was always smaller than that in the untreated soils across the range of pH values tested. These results suggest that the mechanism of action of lime and beringite is similar and probably related to increased metal adsorption and precipitation of metal hydroxides and carbonates at high pH. In the case of red mud, a combination of pH dependent and independent mechanisms (possibly solid-phase diffusion or migration into micropores) may be responsible for the metal fixation observed.

Soil Water Retention on Gold Mine Surfaces in the Mojave Desert

AbstractAn experimental analysis of soil water retention was conducted on three substrates (an abandoned road, an overburden pile, and a heap leach) created by gold mining activities in the Mojave Desert in southeastern California. We mixed each substrate with straw, and the overburden pile and heap leach with growth medium, then applied surface rock mulch to half the plots in an attempt to increase soil water‐holding capacity for revegetation efforts. For each of the six treatments (controls included) we monitored soil water with time domain reflectometry following both a simulation of a rainfall event and a natural rainfall that occurred immediately following the simulation. Both the simulation and the rainfall increased soil water between 3 and 8%, depending on the substrate. Water retention patterns in the two‐week periods following each water addition were similar between the simulation and rainfall, and among all substrate types as values returned to background (pre‐water) conditions. The abandoned road substrate had higher background water content (16.5%) than the overburden pile (6%) and heap leach (5%). The road also had three times higher organic matter and five times higher soil nitrogen than the other two sites. Soil water retention was improved on the overburden pile by the addition of just surface rock mulch or of straw‐plus‐rock mulch. On the heap leach, increases were found with rock mulch only or with growth medium‐plus‐rock mulch. Rock mulches did not improve soil water retention and straw additions decreased soil water on the abandoned road. Judicious use of soil amendments can improve soil water conditions and improve revegetation efforts on disturbed lands in desert environments.

Soil- and plant-based countermeasures to reduce 137Cs and 90Sr uptake by grasses in natural meadows: the REDUP project

The effectiveness of a set of soil- and plant-based countermeasures to reduce 137Cs and 90Sr transfer to plants was tested in natural meadows in the area affected by Chernobyl fallout. Countermeasures comprised the use of agricultural practices (disking+ploughing, liming and NPK fertilisation), addition of soil amendments and reseeding with a selection of grass species. Disking+ploughing was the most effective treatment, whereas the K fertiliser doses applied were insufficient to produce a significant increase in K concentration in soil solution. The application of some agricultural practices was economically justifiable for scenarios with a high initial transfer, such as 137Cs-contaminated organic soils. The use of soil amendments did not lead to a further decrease in transfer. Laboratory experiments demonstrated that this was because of their low radionuclide sorption properties. Finally, experiments examining the effect of plant species on radionuclide transfer showed that both transfer and biomass can depend on the plant species indicating that those with high radionuclide root uptake should be avoided when reseeding after ploughing.

Screening of bacteria for the suppression of Botrytis cinerea and Rhizoctonia solani on lettuce (Lactuca sativa) using leaf disc bioassays

Summary Two leaf disc bioassays were developed for screening bacteria as putative biological control agents of Botrytis cinerea and Rhizoctonia solani on lettuce. Aerobic spore and non-spore forming bacteria were isolated from the phylloplane, rhizoplane and rhizosphere of symptom-free lettuce plants grown in the presence and absence of chitin or composted bark soil amendments. Bacteria, previously isolated from other plants, were also included in the primary screen initially against B. cinerea. One hundred and twenty-seven of 700 isolates reduced botrytis rotting of lettuce leaves by more than 50% in the primary screen. Following a secondary screen against B. cinerea, the lead 50 isolates were also tested for suppression of R. solani infection. Four isolates significantly reduced both botrytis and rhizoctonia leaf rotting. Eleven and five isolates gave control of botrytis and rhizoctonia, respectively, equal to that given by the standard fungicides Rovral WP (iprodione) and Basilex (tolclofos methyl). The two most effective isolates against B. cinerea and R. solani were both identified as Bacillus subtilis. Use of soil amendments did not increase the proportion of efficacious isolates recovered. Effective isolates were originally recovered from roots of oilseed rape and lettuce leaves. In general, it was found that bacteria which controlled one disease effectively did not control the second disease nearly as well. The bioassay protocols developed in this study were used successfully in screening a large number of bacterial isolates in a short time.

Effects of ameliorative measures on the radiocaesium transfer to upland vegetation in the UK

The use of soil amendments to immobilize 137Cs in the soil and/or reduce its uptake by plants was investigated. Field plots in contaminated upland areas of the British Isles (Cwm Eigiau and Corney Fell) was treated with AFCF (ammonium ferric hexacyanoferrate), bentonite, clinoptilolite and muriate of potash (potassium chloride). The 137Cs concentration of vegetation and soil were monitored for three years after treatment. The 137Cs concentration and transfer coefficient of vegetation from both treated and control plots exhibited a seasonal variation with peaks in early summer and were affected by plant species. Some treatments, particularly muriate of potash and clinoptilolite, produced marked reductions in the 137Cs transfer coefficient of the bulk vegetation and individual species especially at Cwm Eigiau.

Persistence of introduced strains of Rhizobium leguminosarum bv trifolii in acidic soils of north-eastern Victoria

Summary. A 5-year study was undertaken to establish if introduced rhizobia with higher tolerance to Al than the current inoculant Rhizobium can persist and continue nodulating subterranean clover (Trifolium subterraneum L.) in acidic soils. Two Rhizobium leguminosarum bv trifolii strains were introduced as seed inoculants with subterranean clover at 2 acidic sites (pHCa 4.1 and pHCa 4.3), where lime and gypsum had been applied as soil amendments. Strain NA3001 was selected for its tolerance to high Al concentrations when grown on an agar medium and WU95, which is a widely used commercial inoculant strain, for its relatively poor tolerance to Al when grown on agar. Liming the soil increased its pH and reduced the concentration of extractable Al at both sites. In the year the subterranean clover was sown, strain WU95 had nodule occupancy of 20–49%, decreasing with time to 4–7% after 5 seasons (1991–95). The nodule occupancy of strain NA3001 was initially lower than strain WU95 (14–16%), but its occupancy did not vary with time (significant strain x time interactions, P&lt;0.05). These data indicate that the acid-tolerant strain NA3001 has the potential to persist in these strongly acidic soils and, despite the presence of high background populations of naturalised rhizobia, to continue initiating nodulation. The use of soil amendments (lime and gypsum) to increase pH and reduce soluble Al concentrations did not affect the nodule occupancy of either NA3001 or WU95 with time, nor did it slow the rate of decline in nodule occupancy of WU95.

Use of Soil Amendments to Reduce Nitrogen, Phosphorus and Heavy Metal Availability

The primary objectives of this study were to determine (1) the exchange characteristics of various soil amendments using a range of salt solutions, (2) the effect of selected soil amendments on heavy metal (Cu2+, Pb2+, and Zn2+) availability, and (3) the effect of selected soil amendments on NH4 + and P availability. The CEC of zeolite and red mud obtained using solutions of 0.1 M BaCl2 and 0.1 M BaCl2/NH4Cl were significantly lower than values obtained using 1 M KCl and 1 M NH4Cl. The higher CEC obtained with monovalent cations indicated that larger divalent cations could not enter the mineralogical framework of zeolite and red mud, and, consequently, a number of exchange sites were only accessible to the smaller monovalent cations. These findings suggest that 1 M KCl and 1 M NH4NO3 should be used as the extracting solutions to obtain the best estimation of CEC and ECEC of red mud and zeolite. The ability of red mud, zeolite, and calcium phosphate (Ca-P), mixed at rates of 0%, 5%, 10%, and 20% (w/w), to sorb Cu2+, Pb2+, and Zn2+ generally followed the order: red mud>zeolite>>Ca-P, while the affinity sequence for these metals followed the order: Pb2+≥Cu2+>>Zn2+. The higher affinity of the sand/amendment mixtures for Pb2+ and Cu2+ relative to Zn2+ was attributed to metal hydrolysis and subsequent specific adsorption as Pb(OH)+ and Cu(OH)+. Zinc was considered to have been primarily sorbed as the divalent cation species. Rates of 5% (w/w) adequately reduced the availability of heavy metals to concentrations below environmental guidelines based on the Toxicity Characteristic Leaching Procedure. Red mud and zeolite added at a rate of 10% (w/w) to the A and B horizon of a sandy soil significantly increased their ability to remove NH4 + from solution, but had negligible effect on P sorption compared with unamended soils. Increased NH4 + removal was attributed to the associated increase in CEC and the greater selectivity of the exchange sites for this cation relative to resident exchangeable Ca2+ and Na+. The absence of P sorption by these two amendments was attributed to the high pH and predominantly negative surface charge of the red mud and the lack of sorption sites in zeolite. Gypsum, on the other hand, tended to depress NH4 + retention but markedly increased P sorption. The depressive effect on NH4 + was due to increased competition between NH4 + and Ca2 + for a limited number of exchange sites, while formation of calcium phosphates of low solubility was the possible mechanism for increased P sorption.

In-Place Inactivation of Pb in Pb-Contaminated Soils

There has been increasing attention to the use of soil amendments and green plants to remediate surface soils contaminated with Pb. We call one form of this technique in-place inactivation. In-place inactivation reduces the hazards associated with contaminated soils through the use of chemicals that change the molecule species of the Pb to stabilize the soil Pb chemically and physically in situ. We have seen significant changes in soil Pb chemistry, Pb leached from soil, and Pb measured by a physiologically based extraction test (PBET) after incorporating inexpensive and readily available materials to three soils. The soils have total Pb concentrations that range from 1200 to 3500 mg kg-1. The leachable soil Pb was significantly reduced in all cases from as high as 30 mg Pb L-1 to below the regulatory limit of 5 mg Pb L-1 after soil treatment. The PBET mimics the mammalian gastric−intestinal tract solutions. In the simulated intestinal phase of the PBET, Pb in solution was reduced by 72% in one of the soi...

TECHNOLOGIES OF AFFORESTATION OF SALT-AFFECTED SOILS

SUMMARY Large areas which have been deteriorated due to soil salinity/alkalinity and waterlogging can be utilized with the planting of salt-tolerant tree species and by making some modifications in land configuration. In the case of alkali soil, the pit auger hole and furrow method is recommended over the pit planting method. The dimension of auger holes will depend on the local soil conditions. The use of soil amendment and farmyard manure (FYM) is necessary to counteract the harmful effect of exchangeable sodium and also to meet plants, nutritional requirements. In contrast to alkali soils, there is no need to have deeper auger holes, and soil amendments such as gypsum, pyrite or sulphuric acid for the establishment of plantations, in saline soils. Even the use of FYM may be avoided. The furrow planting method is preferred over other planting methods. Most of the tree species which were tolerant to alkali soil were also found suitable for saline conditions. Nevertheless, screening of tree species for sp...

Use of soil amendments to reduce soluble phosphorus in dairy soils

The objective of this research was to determine the effectiveness of soil amendments on reducing soluble P in Spodosols under dairy animal land-use. Dairy animal manure is a P source contaminating surface waters of the northern watersheds of Lake Okeechobee in south Florida. Phosphorus contamination has originated from manure-loaded soils found adjacent to milking barns, holding pens, feed lots under intensive animal use, and also developed pastures. In various batch-incubation studies, manure-loaded soils (7.0 to 120.9 g kg −1 t as total organic C) were treated alone or in combination with varying rates of calcium carbonate (to pH 7.5), gypsum (0 to 100 g kg −1 soil), ferrous sulfate (0 to 1000 mg kg −1 as Fe), and alum (0 to 1000 mg kg −1 t as Al). The influence of aerobic and anaerobic conditions on soluble P were also studied. Soluble phosphate concentrations were reduced 40 to 63% from gypsum application up to 100 mg kg −1- t soil; nitrate and soluble organic carbon concentrations were similarily reduced by 45% and 49%, respectively. Increasing water-soluble Ca and the soil pH to 7.5 decreased soluble phosphate concentrations in manure-loaded soils. Gypsum amendments were effective under a broad range of manure loading, pH, and redox conditions. Bacterial activities were also affected by gypsum-amended soils. Calcium carbonate effectiveness was limited to lower pH soils (< pH 7.0). Although Fe and Al soil amendments increased P retention to over 400% from unamended soils, source costs and questionable biological toxicities may limit their usefulness. Evidence indicated that both precipitation and microbial mechanisms are involved in P retention /desorption in soils loaded with animal manures.

Pedigree analysis of the origin of manganese tolerance in Canadian spring wheat (Triticum aestivum L.) cultivars

Breeding wheat (Triticum aestivum L.) for tolerance to manganese (Mn) might be in some cases more feasible and economical than use of soil amendments. As part of research on the heritability of Mn tolerance, a study on the level of Mn tolerance in Canadian wheat cultivars and its probable origin was accomplished by analysis of cultivar pedigrees and drawing phylogenetic maps to discern filial relationships. Cultivar tolerance to Mn was determined by relative root weight (RRW) in solution culture in the presence of 500 μM Mn. A total of 91 cultivars were screened, 76 of which were Canadian. These data, together with data from another 28 cultivars reported in the literature, were used to draw two pedigree maps, a map for Canadian cultivars only, and a map for the Mn-tolerant Canadian cultivars Norquay and Laura. Results indicated a range of tolerance to Mn among Canadian cultivars. Manganese tolerance, found in either Canadian or foreign germplasm, and of either recent or older selection or origin, seems to have originated from land races from Rio Grande do Sul, the southernmost state of Brazil. Tolerance may have been introduced into Canadian germplasm directly by the use of Brazilian cultivars as parents, or indirectly by the introduction of Mexican germplasm with Brazilian parentages. This information will help the plant breeder to develop plant breeding systems, and may also help in the study of the mechanisms for Mn tolerance in wheat.

Reclamation of Red Mud (Bauxite Residues) Using Alkaline‐Tolerant Grasses with Organic Amendments

AbstractDistichlis spicata var. stricta (desert saltgrass), Sporobolus airoides (alkali sacaton), Agropyron smithii (western wheatgrass), and A. elongatum (tall wheatgrass), alkaline‐tolerant grasses of the western United States, were tested as species to colonize and cover red mud (bauxite residue) with minimum use of soil amendments. A gradient in red mud texture at a residue impoundment (coarse at edge to fine in the center) located in Mobile, Ala., was correlated with soil pH that ranged from 9.15 (coarse) to 11.9 (fine). Saturation‐extract Na concentrations ranged from 394 to 4,990 mg/L and Al concentrations from 4.3 to 1,004 mg/L. Exchangeable Na percentage ranged from 52.6 to 91.1. Without amelioration red mud impoundments lacking subsurface drainage remain unvegetated indefinitely. Sewage sludge additions to red mud (2 cm on surface, or 1:2 by volume) produced significantly greater growth compared with red mud controls with D. spicata var. stricta, A. elongatum, and S. airoides in greenhouse pot experiments. Other organic amendments (wheat straw, paper pulp waste, glucose, and pine needles) and complete nutrient additions failed to produce a consistent response. Sewage sludge caused similar growth increases with D. spicata var. stricta in field experiments on drained red mud lakes. Sewage sludge may increase growth via several mechanisms: (i) lowering red mud pH, (ii) adding macro‐ and micronutrients, (iii) increasing nutrient availability through chelation, and (iv) lowering potential Al toxicity.

Notes on the reclamation of salt-affected soils is the Indus Plain of West Pakistan.

About 5, 500, 000 acres of cultivated land in the area are, to varying degrees, damaged by salinity and alkalinity due to waterlogging and under-irrigation in an arid, climate. Most juvenile sedimentary soils of the Indus Plain are calcareous and some of the salt-affected soils, especially in the south, are easily reclaimed because of their high content of divalent cations. In the north, much of the soil is difficult to reclaim because of alkalinity. These latter soils have very low contents of divalent cations, Ca- and Mg carbonates being the only source. Rapid and efficient reclamation will necessitate use of soil amendments. (Abstract retrieved from CAB Abstracts by CABI’s permission)

THE CONTROL OF DISEASES OF LETTUCE BY THE USE OF ANTAGONISTIC ORGANISMS II. THE CONTROL OF RHIZOCTONIA SOLANI KUHN.

The antagonism of a number of bacteria, actinomycetes and fungi in pure culture on soil extract agar has been investigated. A considerable number of each of the three groups were highly antagonistic at 25° C., fewer were active at 15° C. and only a very limited number were effective at 5° C.In greenhouse experiments damping‐off of lettuce seedlings was substantially controlled by selected antagonists in sterile sand, soil or in sand/soil mixtures. Under similar conditions in unsterile soil, forms highly antagonistic in pure culture were generally ineffective in controlling disease. In one experiment control of disease in natural soil was obtained by the use of soil amendments, the effect being enhanced by the inoculation of one of these amendments with suspensions of antagonists.Attempts to control disease in the field by the use of soil amendments are described. In one year a substantial increase in the stand of healthy seedlings was obtained with certain treatments.

The effect of mineral supply on the mineral concentration and nutritional quality of plants

The mineral composition of plants is a function of many factors, such as difference in soils, use of soil amendments or fertilizers, and rainfall and other climatic influences. These factors overlap in their effects or work simultaneously. One factor may influence another. Thus, the effect of climate on the plant is partly direct and partly the result of the development by climatic factors of certain soil characteristics. Differences in these factors will naturally operate to modify the mineral composition of the plant in different ways. For example, it is possible (a) for the mineral composition of two plants of the same variety growing in different soils to be significantly different without there being any important difference in their size or the distribution of their parts, such as leaf, stem or seed head; (b) for the growth (yield) of plants of the same variety to vary in different soils without any important differences in the proportions of the parts of the plants; (c) for two plants of the same variety growing in different soils to have quite different distributions of leaf, stem or head; and (d) for environmental factors to so modify the quantities of plant constituents such as protein, carbohydrate, lignin and cellulose as to influence the percentage distribution of other constituents, as by a deposition of starch with a consequent reduction in the percentage composition of the mineral elements. The properties of two soils may be such as to modify the natural flora and thus to produce plants quite different in mineral composition. The evaluation of the influence of these factors on plant composition is still proceeding, and much valuable information of fundamental importance is being obtained. The nutritional diseases of animals which have been traced to soil characteristics may be divided into two general classes. The first,