Activity of nitrifying populations in grassland soil polluted by polychlorinated biphenyls (PCBs)

The activity of nitrification was studied in the period of 1992 – 1994 in two grassland plots from the surroundings of a municipal waste incinerator. The soil parameters were fully comparable in both plots and the soils differed in the level of polychlorinated biphenyls (PCBs). The concentration of PCBs found in Klajdovka-control plot (KL): 4.4 ng g_{dry soil} ^–1 can be regarded as a background value, while the polluted plot, Bílá Hora (BH), contained increased amount of PCBs: 14.0 ng g_{dry soil} ^–1.The following parameters of nitrifying activity were determined: field concentrations of N_inorg species, mineralization potentials, nitrifying activity during long-term laboratory incubations, and the potential activity of both ammonium and nitrite oxidizers in short-term incubations in soil slurries. Simultaneous application of all these methods appeared to be very suitable for reliable assessment of nitrifying activity in the field.In the case of the polluted plot, the abnormal accumulation of nitrite was observed both in the field (e.g. in September 1992: BH-656.8 ng NO _inf2 ^– -N g_{dry soil} ^–1; KL-208.2 ng NO _inf2 ^– -N g_{dry soil} ^–1) and in the laboratory incubations. Furthermore, the capability of the polluted plot to nitrify higher amount of ammonium nitrogen appeared to be significantly reduced due to detrimental changes in the activity of nitrite-oxidizing community. In contrast to the nitrification, the mineralization potential did not differ between the plots throughout the sampling period.     

Copper uptake and phytotoxicity as assessed in situ for durum wheat (Triticum turgidum durum L.) cultivated in Cu-contaminated, former vineyard soils

This work assessed in situ, copper (Cu) uptake and phytotoxicity for durum wheat (Triticum turgidum durum L.) cropped in a range of Cu-contaminated, former vineyard soils (pH 4.2–7.8 and total Cu concentration 32–1,030 mg Cu kg⁻¹) and identified the underlying soil chemical properties and related root-induced chemical changes in the rhizosphere. Copper concentrations in plants were significantly and positively correlated to soil Cu concentration (total and EDTA). In addition, Cu concentration in roots which was positively correlated to soil pH tended to be larger in calcareous soils than in non-calcareous soils. Symptoms of Cu phytotoxicity (interveinal chlorosis) were observed in some calcareous soils. Iron (Fe)–Cu antagonism was found in calcareous soils. Rhizosphere alkalisation in the most acidic soils was related to decreased CaCl₂-extractable Cu. Conversely, water-extractable Cu increased in the rhizosphere of both non-calcareous and calcareous soils. This work suggests that plant Cu uptake and risks of Cu phytotoxicity in situ might be greater in calcareous soils due to interaction with Fe nutrition. Larger water extractability of Cu in the rhizosphere might relate to greater Cu uptake in plants exhibiting Cu phytotoxic symptoms.     

Solubilization and Plant Uptake of Zinc and Cadmium from Soils Treated with Elemental Sulfur

In growth chamber experiments we studied the potential use of elemental sulfur (S₈) as an acidifying agent to enhance the uptake of Cd and Zn from three different polluted soils by candidate phytoremediation plants (Brassica juncea, Helianthus annuus, Salix viminalis). Two of the three soils were calcareous, the other slightly acidic. One of the calcareous soils had been contaminated by dust emissions from a nearby brass smelter. The pollution of the other two soils had resulted from sewage sludge applications.

Sulfur was added to soils in quantities of 20 to 400 mmol sulfur kg^-1 soil. Plants were grown under fluorescent light in 1.5 l ($OS 13 cm) pots for 28 d.

Within 700 h soil pH decreased significantly in all soils, depending on S₈ dosage. In the acid soil, pH decreased from pH 6.5 to about 4 at the highest treatment level, while pH in one of the calcareous soils dropped even below pH 4. The effect was smaller in the second calcareous soil.

NaNO₃-extractable Cd and Zn increased up to 26-and 13-fold, respectively, in the acid soil, while in the calcareous soils, maximum increases were 9-and 11-fold, respectively.

Increased NaNO₃-extractable concentrations translated well into shoot concentrations (dry matter) in plants. Shoot Zn concentrations in H. annuus, for example, increased from 930 in the controls to 4300 mg kg^-1 in the highest S₈ treatment. However, effects observed in the plants were generally smaller than in the soils. In addition, in some variants growth was negatively affected, resulting in reduced metal removal from the soils.     

Soil Nitrogen Fertilization Effects on Phytoextraction of Cadmium and Lead by Tobacco (Nicotiana tabacum L.)

A greenhouse experiment using 24 plastic pots filled with 6 kg of Pb- and Cd-contaminated soil was carried out. In all 24 pots, soils were heavy metal–contaminated with 10 mg Cd kg^?1 soil and 500 mg of Pb kg^?1 soil by using CdCl and PbNO₃. Two-month-old tobacco (Nicotiana tabacum L.) plants were used to extract these heavy metals. Results showed that tobacco is able to remove Cd and Pb from contaminated soils and concentrate them in its harvestable part, that is, it could be very useful in phytoextraction of these heavy metals. Increasing additions of ammonium nitrate to soil (50, 100, and 150 mg N kg^?1 soil) significantly (p ≤ .05) increased aboveground Cd and Pb accumulation during a 50-day experimental period, whereas increasing additions of urea to soil (50 and 100 mg N kg^?1 soil) did not show these effects at the same significance levels. Increasing additions of ammonium nitrate to soil shows as dry matter increases, both accumulated Cd and accumulated Pb also increase when tobacco plants are growing under Pb- and Cd-contaminated soil conditions. Higher Pb concentrations depress Cd/Pb ratios for concentrations and accumulations, suggesting that Pb negatively affects Cd concentration and/or accumulation.     

Effects of Cadmium,Copper, Lead,and Zinc Contamination on Metal Accumulation by Safflower and Wheat

Accumulation of heavy metals (HMs) in cultivated soils is a continuing environmental problem in many parts of the world. An increase in HM concentration can enhance uptake of toxic metals by crops and enter the human food chain. In this study, the uptake behavior of wheat and safflower was evaluated in a calcareous soil by using 12 undisturbed columns in which half were artificially contaminated. Heavy metals in the form of CdCl₂ (15 mg Cd kg^{? 1}), CuSO₄ (585 mg Cu kg^{? 1}), Pb(NO₃)₂ (117 mg Pb kg^{? 1}), and ZnCl₂ (1094 mg Zn kg^{? 1}) were sprayed on the soil surface and completely mixed in the top 10 cm. The background total concentrations of Cd, Cu, Pb and Zn were 1.6, 29.5, 17.5 and 61.2 mg kg^{? 1}, respectively. After metal application, half of the columns (3 contaminated and 3 uncontaminated) were sown with wheat (Triticum aestivum) and the other half with safflower (Carthamus tinctorious) and grown for 74 days until maturity. After harvesting, soil columns were cut into 10-cm sections and analyzed for HNO₃- and DTPA-extractable metal concentrations. Metal concentrations were also measured in different plant tissues. The results showed that artificial contamination of topsoil decreased the transpiration rate of wheat by 12% and that of safflower by 6%. In contaminated columns, Cd, Cu, Pb, and Zn accumulation in wheat shoot was greater by 8.0-, 1.9-, 3.0-, and 2.1-fold than the control, respectively. Accordingly, these numbers were 46.0-, 1.3-, 1.7-, and 1.6-fold in safflower shoot. Soil contamination with HMs resulted in a 55% decrease in shoot dry matter yield of wheat while it had no significant effect on shoot dry matter of safflower. The normalized water consumption for safflower was therefore not affected by metal contamination (≈ 13 mm H₂O g^{? 1} of dry weight for all safflower and uncontaminated wheat treatments), while contaminated wheat was much less water efficient at about 27 mm H₂O g^{? 1} dry weight. It was concluded that although artificial contamination had a negative effect on wheat growth, it did not affect safflower's normal growth and water efficiency.     

Accumulation of cadmium and selected elements in flax seed grown on a calcareous soil

Seed of flax (Linum usitatissimum L.) grown on calcareous and neutral soils sometimes accumulates relatively high concentrations of Cd. The influence of a post-flowering application of NH₄NO₃ (115 mg N kg^-1), CdSO₄ (1 mg Cd kg^-1), FeEDDHA (2 mg Fe kg^-1), NaH₂PO₄ (120 mg P kg^-1) and ZnSO₄ (8 mg Zn kg^-1) on seed accumulation of Cd, Fe, N, Mn, P and Zn by flax grown on a Calciaquoll was studied in two experiments under greenhouse conditions. Seed yields were increased by the N and Zn treatments, and the N×Zn interaction was positive. Zinc deficiency delayed flowering and boll formation by up to 20 days and reduced seed size. In the absence of added Cd, seed accumulated up to 0.33 mg Cd kg^-1. This Cd accumulation was reduced by approximately 50 and 17% by added Zn and Fe, respectively, but was little affected by P fertilizer and post-flowering N stress. In the presence of added Cd, seed Cd exceeded 3.3 mg Cd kg^-1, and the antagonistic effects of Fe and Zn on seed Cd were absent. Seed N, P, Fe and Zn concentrations were increased on average by 10, 45, 31 and 97% by the N, P, Fe and Zn fertilizer treatments, respectively. FeEDDHA reduced seed Mn concentration by approximately 58%. However, seed Mn concentration was much less than that found in vegetative tissue at flowering. Soil-applied Zn may reduce seed Cd concentration in flax under field conditions, and may increase marketability of flax for food use.     

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg^-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg^-1 soil) applied as CdSO₄ and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg^-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg^-1 (control plants) to 505.7 mg kg^-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg^-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 g kg^-1 of fresh weight.Contribution no. 951     

Field Evidence of Cadmium Phytoavailability Decreased Effectively by Rape Straw and/or Red Mud with Zinc Sulphate in a Cd-Contaminated Calcareous Soil

To reduce Cd phytoavailability in calcareous soils, the effects of soil amendments of red mud, rape straw, and corn straw in combination with zinc fertilization on Cd extractability and phytoavailability to spinach, tomato, Chinese cabbage and radish were investigated in a calcareous soil with added Cd at 1.5 mg kg⁻¹. The results showed that water soluble and exchangeable Cd in soils was significantly decreased by the amendments themselves from 26% to 70%, which resulted in marked decrease by approximately from 34% to 77% in Cd concentration in vegetables. The amendments plus Zn fertilization further decreased the Cd concentration in vegetables. Also cruciferous rape straw was more effective than gramineous corn straw. In all treatments, rape straw plus red mud combined with Zn fertilization was most effective in decreasing Cd phytoavailability in soils, and it is potential to be an efficient and cost-effective measure to ensure food safety for vegetable production in mildly Cd-contaminated calcareous soils.     

Phytoextraction Potential of Poplar (Populus alba L. var. pyramidalis Bunge) from Calcareous Agricultural Soils Contaminated by Cadmium

To investigate the phytoextraction potential of Populus alba L. var. pyramidalis Bunge for cadmium (Cd) contaminated calcareous soils, a concentration gradient experiment and a field sampling experiment (involving poplars of different ages) were conducted. The translocation factors for all experiments and treatments were greater than 1. The bioconcentration factor decreased from 2.37 to 0.25 with increasing soil Cd concentration in the concentration gradient experiment and generally decreased with stand age under field conditions. The Cd concentrations in P. pyramidalis organs decreased in the order of leaves > stems > roots. The shoot biomass production in the concentration gradient experiment was not significantly reduced with soil Cd concentrations up to or slightly over 50 mg kg^–1. The results show that the phytoextraction efficiency of P. pyramidalis depends on both the soil Cd concentration and the tree age. Populus pyramidalis is most suitable for remediation of slightly Cd contaminated calcareous soils through the combined harvest of stems and leaves under actual field conditions.     

Enhanced phytoremediation of cadmium and/or benzo(a)pyrene contaminated soil by hyperaccumlator Solanum nigrum L.

The role of same amendment on phytoremediating different level contaminated soils is seldom known. Soil pot culture experiment was used to compare the strengthening roles of cysteine (CY), EDTA, salicylic acid (Sa), and Tween 80 (TW) on hyperaccumulator Solanum nigrum L. phytoremediating higher level of single cadmium (Cd) or Benzo(a)pyrene (BAP) and their co-contaminated soils. Results showed that the Cd capacities (ug pot^?1) in shoots of S. nigrum in the combined treatment T_{0.1EDTA+0.9CY} were the highest for the 5 and 15 mg kg^?1 Cd contaminated soils. When S. nigrum remediating co-contaminated soils with higher levels of Cd and BAP, that is, 5 mg kg^?1 Cd + 1 mg kg^?1 BAP and 15 mg kg^?1 Cd + 2 mg kg^?1 BAP, the treatment T_{0.9CY+0.9Sa+0.3TW} showed the best enhancing remediation role. This results were different with co-contaminated soil with 0.771 mg kg^?1 Cd + 0.024 mg kg^?1 BAP. These results may tell us that the combine used of CY, SA, and TW were more useful for the contaminated soils with higher level of Cd and/or BAP. In the combined treatments of Sa+TW, CY was better than EDTA.     

Arsenic accumulation of common plants from contaminated soils

A pot experiment was conducted to investigate the relationship between soluble concentrations of arsenic (As) in soil and its accumulation by maize (Zea mays), English ryegrass (Lolium perenne), rape (Brassica napus) and sunflower (Helianthus annuus) on two different soils: a calcareous Regosol (silty loam) and a non-calcareous Regosol (sandy loam). Arsenic (Na₂HAsO₄·7H₂O) was applied to obtain comparable soluble As concentrations in the two soils. In both soils, soluble As concentrations, extracted with 0.1 M NaNO₃, were found to correlate better with As concentrations in plants after 4 month of growth than total soil concentrations, extracted with 2 M HNO₃. With all four plant species, the relationship between the soluble As concentration in the soil and As that in the plants was non- linear, following Michaelis-Menten kinetics. Similar soluble As concentrations in the two soils did not result in a similar As concentration in the plants. Except for maize, arsenic transport from roots to shoots was significant, resulting in As concentrations in the leaves and grains above the Swiss tolerance limits for fodder and food crops (4 and 0.2 mg As kg^–1, respectively). Based on these results we suggest that beside As solubility, P availability and P demand, which are plant specific, have to be taken into account to predict the uptake of As by crop plants from As contaminated soils and to predict the risk of arsenic entering into the food chain.     

Nitrogen cycling in a flooded-soil ecosystem planted to rice (Oryza sativa L.)

¹⁵N studies of various aspects of the nitrogen cycle in a flooded rice ecosystem on Crowley silt loam soil in Louisiana were reviewed to construct a mass balance model of the nitrogen cycle for this system. Nitrogen transformations modeled included 1) net ammonification (0.22 mg NH₄ ⁺?N kg dry soil^?1 day^?1), 2) net nitrification (2.07 mg NO₃ ^??N kg^?1 dry soil^?1 day^?1), 3) denitrification (0.37 mg N kg dry soil^?1 day^?1), and 4) biological N₂ fixation (0.16 mg N kg dry soil^?1 day^?1). Nitrogen inputs included 1) application of fertilizers, 2) incorporation of crop residues, 3) biological N₂ fixation, and 4) deposition. Nitrogen outputs included 1) crop removal, 2) gaseous losses from NH₃ volatilization and simultaneous occurrence of nitrification-denitrification, and 3) leaching and runoff. Mass balance calculations indicated that 33% of the available inorganic nitrogen was recovered by rice, and the remaining nitrogen was lost from the system. Losses of N due to ammonia volatilization were minimal because fertilizer-N was incorporated into the soil. A significant portion of inorganic-N was lost by ammonium diffusion from the anaerobic layer to the aerobic layer in response to a concentration gradient and subsequent nitrification in the aerobic layer followed by nitrate diffusion into the anaerobic layer and denitrification into gaseous end products. Leaching and surface runoff losses were minimal.     

Immobilization and phytoavailability of cadmium in variable charge soils. I. Effect of phosphate addition

The effect of phosphate on the surface charge and cadmium (Cd) adsorption was examined in seven soils that varied in their variable-charge components. The effect of phosphate on immobilization and phytoavailability of Cd from one of the soils, treated with various levels of Cd (0–10 mg Cd kg^–1 soil), was further evaluated using mustard (Brassica juncea L.) plants. Cadmium immobilization in soil was evaluated by a chemical fractionation scheme. Addition of phosphate, as KH₂PO₄, increased the pH, negative charge and Cd adsorption by the soils. Of the seven soils examined, the three allophanic soils (i.e., Egmont, Patua and Ramiha) exhibited greater increases in phosphate-induced pH, negative charge and Cd²⁺ adsorption over the other four non-allophanic soils (i.e., Ballantrae, Foxton, Manawatu ad Tokomaru). Increasing addition of Cd enhanced Cd concentration in plants, resulting in decreased plant growth (i.e., phytotoxicity). Addition of phosphate effectively reduced the phytotoxicity of Cd. There was a significant inverse relationship between dry matter yield and Cd concentration in soil solution. Addition of phosphate decreased the concentration of the soluble + exchangeable Cd fraction but increased the concentration of inorganic-bound Cd fraction in soil. The phosphate-induced alleviation of Cd phytotoxicity can be attributed primarily to Cd immobilization due to increases in pH and surface charge.     

Reduction of Cadmium Availability to Tobacco (Nicotiana tabacum) Plants using Soil Amendments in Low Cadmium-contaminated Agricultural Soils: A Pot Experiment

Cadmium (Cd) concentration in field-grown tobacco leaves usually ranges from < 0.5 to 5 mg Cd kg^–1 dry matter (DM). Reducing bioavailability of soil Cd by adding amendments to the soil could be suitable to mitigate Cd uptake by tobacco plants. However, little is known on the effect of inorganic amendments on agricultural soils with low Cd concentrations. Therefore, we performed a pot experiment with tobacco plants that were grown during 56 days in two neutral to alkaline agricultural soils with low total Cd concentrations (soil 1 = 0.4, soil 2 = 0.7 mg kg^–1). Both soils were amended or not with 1 or 5% of sepiolite, zeolite, hydroxyapatite and apatite II™. Major and trace elements were measured in mid-stalk position leaves. Soil metals were measured in a DTPA soil extraction to assess the effect of the amendments on metal bioavailability. Some amendments significantly reduced Cd concentration in tobacco leaves, but the effect differed between the two soils tested. In soil 1, the use of zeolite at the 1% dose was the most efficient, reducing the average Cd concentration from 0.6 to 0.4 mg kg^–1. In soil 2, the 5% hydroxyapatite treatment led to the maximal reduction in Cd concentration (50%), with an average final Cd concentration in leaves of 0.7 mg kg^–1 (control: 1.5 mg kg^–1). There was a dose effect for some amendments in soil 2 (containing more Cd), suggesting a reduced efficiency of the amendment at the lowest addition rate. DTPA extractable Cd and Zn measured at the end of the pot experiment were correlated to the metal concentrations in tobacco leaves suggesting that (1) the reduction in leaf Cd concentration was due to a reduction in metal availability to tobacco and (2) DTPA may be a suitable extractant to estimate Cd availability to tobacco plants in these two soils. In addition, a batch experiment was performed with the same soils to test a larger number of amendments, including the four tested in the pot experiment. Results were compared to those of the pot experiment to assess whether a batch experiment may predict the efficiency of an amendment on a given soil. It gave results compatible with those from the pot experiment except for the sepiolite and highlighted the broad range of potential amendments available for heavy metal remediation in crop plants.     

Cd AND Zn ACCUMULATION IN PLANTS FROM THE PADAENG ZINC MINE AREA

Significant cadmium (Cd) contamination In soil and rice has been discovered in Mae Sot, Tak province, Thailand where the rice-based agricultural systems are established in the vicinity of a zinc mine. The prolonged consumption of Cd contaminated rice has potential risks to public health and health impacts of Cd exposed populations in Mae Sot have been demonstrated. The Thai government has prohibited rice cultivation in the area as an effort to prevent further exposure. Phytoextraction, the use of plants to remove contaminants from soil, is a potential option to manage Cd–contaminated areas. However, successful phytoextraction depends on first identifying effective hyperaccumulator plants appropriate for local climatic conditions. Five sampling sites at Padaeng Zinc mine, Tak province were selected to collect plant and soil samples. Total Cd and Zn concentrations in sediments or soils were approximately 596 and 20,673 mg kg^?1 in tailing pond area, 543 and 20,272 mg kg^?1 in open pit area, 894 and 31,319 mg kg^?1 in stockpile area, 1,458 and 57,012 mg kg^?1 in forest area and 64 and 2,733 mg kg^?1 in Cd contaminated rice field. Among a total of 36 plant species from 16 families, four species (Chromolaena odoratum, Gynura pseudochina, Impatiens violaeflora and Justicia procumbens) could be considered as Cd hyperaccumulators since their shoot Cd concentrations exceeded 100 mg Cd kg^?1 dry mass and they showed a translocation factor > 1. Only Justicia procumbens could be considered as a Zn hyperaccumulator (Zn concentration in its shoot more than 10,000 mg Zn kg^?1 dry mass with the translocation factor > 1).     

Large Scale Spatial Variability of Accumulated Cadmium in the Wheat Farm Grains

Cadmium (Cd) accumulation in edible crops is undesirable due to its hazardous influences on human health. The objectives of this study were: i) to evaluate the spatial variability of grain Cd and its relationships with soil properties in 4000 km² wheat farms; ii) to evaluate the effect of wheat cultivar on the soil properties vs. grain Cd relationships. A number of 255 soil (0–20 cm) and grain samples were taken and Cd concentrations in grain samples and some soil properties were measured. Grain Cd concentrations in 95 percent of the samples exceeded the threshold of 0.2 mg kg^?1. Durum wheat had more potential to accumulate Cd in grain (0.76 mg kg^?1) than bread (0.69 mg kg^?1). There was significant (p < 0.01) correlation between grain Cd and organic carbon (r = 0.66), CEC (r = 0.77) and DTPA-extractable Cd (p < 0.05) (r = 0.57) of the soils. Greater Pearson coefficient values for durum wheat showed that, in the studied calcareous soils, organic carbon, CEC, Cd-DTPA had more effects on durum wheat than bread wheat cultivar. The obtained Kriging map of grain Cd identified three hotspots at the east (durum wheat cultivation), the west (intensive irrigated wheat farms), and south (wheat farms around petrochemical industries) of the region. Agricultural mismanagement due to overusing P-fertilizers increased Cd concentration in the topsoils and grains of wheat farms in the study area.     

Zinc deficiency as a critical problem in wheat production in Central Anatolia

In a soil and plant survey, and in field and greenhouse experiments the nutritional status of wheat plants was evaluated for Zn, Fe, Mn and Cu in Central Anatolia, a semi-arid region and the major wheat growing area of Turkey.All 76 soils sampled in Central Anatolia were highly alkaline with an average pH of 7. 9. More than 90% of soils contained less than 0.5 mg kg^-1 DTPA-extractable Zn, which is widely considered to be the critical deficiency concentration of Zn for plants grown on calcareous soils. About 25% of soils contained less than 2.5 mg kg^-1 DTPA-extractable Fe which is considered to be the critical deficiency concentration of Fe for plants. The concentrations of DTPA-extractable Mn and Cu were in the sufficiency range. Also the Zn concentrations in leaves were very low. More than 80% of the 136 leaf samples contained less than 10 mg Zn kg^–1. By contrast, concentrations of Fe, Mn and Cu in leaves were in the sufficient range.In the field experiments at six locations, application of 23 kg Zn ha^-1 increased grain yield in all locations. Relative increases in grain yield resulting from Zn application ranged between 5% to 554% with a mean of 43%. Significant increases in grain yield (more than 31%) as a result of Zn application were found for the locations where soils contained less than 0.15 mg kg^-1 DTPA-extractable Zn.In pot experirnents with two bread (Triticum aestivum, cvs. Gerek-79 and Kirac-66) and two durum wheats (Triticum durum, cvs. Kiziltan-91 and Kunduru-1149), an application of 10 mg Zn kg^-1 soil enhanced shoot dry matter production by about 3.5-fold in soils containing 0.11 mg kg^-1 and 0.15 mg kg^-1 DTPA-extractable Zn. Results from both field observations and greenhouse experiments showed that durum wheats were more susceptible to Zn deficiency than the bread wheats. On Zn deficient soils, durum wheats as compared to bread wheats developed deficiency symptoms in shoots earlier and to a greater extent, and had lower Zn concentration in shoot tissue and lower Zn content per shoot than the bread wheats.The results presented in this paper demonstrate that (i) Zn deficiency is a critical nutritional problem in Central Anatolia substantially limiting wheat production, (ii) durum wheats possess higher sensitivity to Zn deficient conditions than bread wheats, and (iii) wheat plants grown in calcareous soils containing less than 0.2 mg kg^-1 DTPA-extractable Zn significantly respond to soil Zn applications. The results also indicate that low levels of Zn in soils and plant materials (i.e. grains) could be a major contributing factor for widespread occurrence of Zn deficiency in children in Turkey, whose diets are dominated by cereal-based foods.     

Characterization of Bacteria in the Rhizosphere Soils of Polygonum Pubescens and Their Potential in Promoting Growth and Cd,Pb, Zn Uptake by Brassica napus

Microbe-enhanced phytoremediation has been considered as a promising measure for the remediation of metal-contaminated soils. In this study, two bacterial strains JYX7 and JYX10 were isolated from rhizosphere soils of Polygonum pubescens grown in metal-polluted soil and identified as of Enterobacter sp. and Klebsiella sp. based on 16S rDNA sequences, respectively. JYX7 and JYX10 showed high Cd, Pb and Zn tolerance and increased water-soluble Cd, Pb and Zn concentrations in culture solution and metal-added soils. Two isolates produced plant growth-promoting substances such as indole acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and solubilized inorganic phosphate. Based upon their ability in metal tolerance and solubilization, two isolates were further studied for their effects on growth and accumulation of Cd, Pb, and Zn in Brassica napus (rape) by pot experiments. Rapes inoculated with JYX7 and JYX10 had significantly higher dry weights, concentrations and uptakes of Cd, Pb, Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg^?1), Pb (200 mg kg^?1) or Zn (200 mg kg^?1). The present results demonstrated that JYX7 and JYX10 are valuable microorganism, which can improve the efficiency of phytoremediation in soils polluted by Cd, Pb, and Zn.     

Vital evidence for arbuscular mycorrhizal fungi,bacteria and cattail plant to remove Pb-Cd heavy metals from contaminated soils

Phytoremediation is a low-cost but highly efficient and environmentally friendly technology for heavy metal soil remediation. However, its success in soils is dependent on the chosen plant and microbes. Moreover, the effect of mycorrhizal fungi and bacteria on CO₂ release, mineralization rate, and metal translocation in cadmium and lead-contaminated cattails plant is unknown. The goal of the research was to look into the effects of bacteria, mycorrhiza, and cattails on CO₂ release, mineralization rate, lead (Pb), and cadmium (Cd) removal from soil. The experiment used six different combinations (mycorrhiza, bacillus 10 mL, bacillus 100 mL, mycorrhiza + bacillus 10 mL, mycorrhiza + bacillus 100 mL, and control). The results showed that combining mycorrhiza with bacillus 100 mL resulted in greater increases in CO₂ release, polysaccharides content and mineralization rate (2.84 mg CO₂ g^?1 in dry soil, 0.90 mg, 0.021 mg C g^?1 dry soil day^?1). More crucially, mycorrhiza + bacillus 100 mL roots had the greatest quantities of Cd and Pb (18.26 mg kg^?1 and 155.22 mg kg^?1), showing that bacteria had a prominent part in the phytoextraction process. Regarding Cd, the bacillus 100 mL had the highest translocation factor (TF) (3.99) and biological accumulation factor (BAF) (75.54), indicating effective translocation and excessive Cd accumulation in the plant. Bacillus 100 and mycorrhiza + bacillus 100 had the highest Pb TF (0.49) and BAF (6.08). Ultimately, the elimination of Cd and Pb was linked to the maximum bacterial cell density, mycorrhizal activity, and CO₂ emission, resulting in a unique phytoremediation in Pb-Cd contaminated cattails rhizosphere soils.     

Nitrogen and phosphorus requirements for raising mycorrhizal seedlings of Leucaena leucocephala in containers

A greenhouse study was undertaken to determine the nitrogen and phosphorus fertilization requirements for raising mycorrhizal seedlings in soil in containers. Seedlings of Leucaena leucocephala were grown for 40 days in dibble tubes containing fumigated or nonfumigated soil uninoculated or inoculated with Glomus aggregatum. The soil was fertilized with NH₄NO₃ solution to obtain 25–200 mg N kg^-1 soil, and with a KH₂PO₄ solution to establish target soil solution P concentrations of 0.015–0.08 mg P l^-1. At the end of 40 days, seedlings were transplanted into pots containing 5-kg portions of fumigated soil. Posttransplant vesicular arbuscular mycorrhizal fungal (VAMF) effectiveness, measured as pinnule P content, plant height, shoot dry weight and tissue N and P concentrations, was significantly increased by pretransplant VAMF colonization in both soils. The best posttransplant mycorrhizal colonization and mycorrhizal growth responses were observed if the nonfumigated pretransplant soil was amended with 50 mg N kg^-1 soil and 0.04 mg P l^-1 or if the fumigated pretransplant soil was amended with 100 mg N kg^-1 soil and 0.04 mg P 1^-1. There was no relationship between NP ratios of nutrients added to the pretransplant soil medium and shoot NP ratios observed after transplanting. Shoot NP ratio was also not correlated with root colonization level.Contribution from the Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 4025