Plant Zn Concentration Research Articles

Evaluation of Efficacy of ZnO Nanoparticles as Remedial Zinc Nanofertilizer for Rice

Zinc (Zn) is an important element of nutritional significance to humans, animals, and plants. The impact of zinc oxide nanoparticles (ZnONPs) foliar spray at four different concentrations, viz. 0, 0.5, 1.0 and 5.0 g L−1 at 15-day interval on rice crop cv. PR-121 grown in Zn-deficient soil was assessed in a pot study for remediation of Zn deficiency and enhanced Zn fortification. The soil samples were analyzed for chemical properties, culturable microbial counts, dehydrogenase activity and plant vegetative characteristics, yield, and nutrient profile while the leaf samples were analyzed by scanning EM imaging and SEM-EDS techniques. The leaf surface after foliar spray showed the presence of ZnONPs on the leaf lamina near stomatal openings. The foliar application of ZnONPs (@ 5.0 g L−1) significantly improved the growth and yield parameters. However, root characteristics attained the highest values at 1.0 g L−1 ZnONPs application. The soil microbial counts and enzyme activities such as viable cell counts and dehydrogenase activity were observed to be the highest at 5.0 g L−1 ZnONPs treatment. Overall, ZnONPs treatments successfully reverted the Zn-deficiency symptoms besides enhancing the plant Zn contents, though the response was concentration dependent. These findings indicate that ZnONPs can be effectively used for remediation and Zn fortification in rice cultivated under low soil Zn concentrations.

Zinc Application Enhances Superoxide Dismutase and Carbonic Anhydrase Activities in Zinc-Efficient and Zinc-Inefficient Wheat Genotypes

Deficiency of zinc (Zn) in soils and crops of the world is established fact. There is need for application of Zn application and growing Zn-efficient crop genotypes to tide over the situation. However, information pertaining to application of Zn to Zn-efficient and Zn-inefficient crop genotypes grown in field condition on plant enzyme (wherein Zn is a co-factor) activities is limited. To investigate the influence of different Zn regimes on superoxide dismutase (SOD) and carbonic anhydrase (CA) activities of Zn-efficient and Zn-inefficient wheat genotypes, the present study was carried out comprising three each of Zn-efficient and Zn-inefficient genotypes of wheat grown under field experiment with four Zn treatments such as no Zn, soil Zn, foliar Zn, and both soil and foliar Zn. Application of Zn (soil/foliar/both) enhanced SOD and CA activities of both Zn-efficient and Zn-inefficient genotypes at pre- and post-anthesis growth stages of wheat compared to no Zn. Under no Zn, SOD activities were higher in both Zn-efficient and Zn-inefficient genotypes at post-anthesis stage; however, reverse was true for CA activities. Application Zn enhanced Zn concentration in leaves, stem, and grain of both Zn-efficient and Zn-inefficient genotypes. Grain Zn concentration increased by 25.1, 35.7, and 38.2% with soil, foliar, and both soil and foliar applications of Zn, respectively in Zn-inefficient genotypes and by 7.2, 21.1, and 30.6% with soil, foliar, and both and foliar applications of Zn, respectively in Zn-efficient genotypes, compared to no Zn. In Zn-efficient genotypes, SOD and CA activities contributed about 63 and 77% towards grain Zn concentration, respectively, whereas SOD and CA activities contributed about 50 and 66% towards grain Zn concentration, respectively in Zn-inefficient genotypes. The results indicated that both soil and foliar applications are needed for enhanced SOD and CA activities and plant Zn concentration in wheat. Physiological utilization of Zn plays an important role in Zn efficiency of wheat genotypes.

Gneiss and steatite vermicomposted with organic residues: release of nutrients and heavy metals

PurposeUse of silicate rock powders as fertilizer improves nutrient cycling, thus benefitting agriculture. The availability of nutrients to plants is often low, but can be increased when rock powder is vermicomposted and added. However, these powders can be rich in heavy metals, which may impair their use. We evaluated maize growth and heavy metals in plants and soil after fertilization with vermicomposted gneiss or steatite powders.MethodVermicompost was prepared with cattle manure, with or without gneiss or steatite powders. The experimental units were kept in the dark at room temperature for 70 days. Subsequently, a greenhouse experiment was carried out with maize grown in highly weathered oxisol soil and fertilized with vermicompost alone, or with gneiss or steatite powder.ResultsA small proportion of heavy metals was immobilized in the earthworm bodies, but did not hinder their growth. Maize growth was superior in the treatment with vermicomposted gneiss powder. The gneiss-enriched treatment contributed to increased Zn concentration in plants and may also be an alternative to Zn fertilization. High Ni and Cr concentrations in steatite powder apparently induced higher levels of these elements in plants. However, metal concentrations in the soil after cultivation in all the treatments were below acceptable limits.ConclusionIncreased plant growth in gneiss-enriched vermicompost suggests the possibility of using this material to enrich vermicompost with nutrients, thus improving the chemical quality of organic fertilizer. Use of steatite powder in agriculture deserves further investigation.

Assessment of using bentonite, dolomite, natural zeolite and manure for the immobilization of heavy metals in a contaminated soil: The Copșa Mică case study (Romania)

The aim of study was to assess the effectiveness of organic and inorganic amendments to immobilize cadmium (Cd), lead (Pb) and zinc (Zn) in soil and reduce their availability in a contaminated soil. We present the results of a field experiment organised in the Copșa Mica area in which different types of amendments were applied: Na-bentonite, dolomite, natural zeolite and manure. The effectiveness of applied amendments was assessed using single extraction of metals from soil (using DTPA-CaCl2-TEA at pH 7.3 or NH4NO3) and metal accumulation in plants. All treatments produced significant increases of soil pH, but the best results were observed after applications of dolomite and Na-bentonite. After two years from applications all amendments decreased the metal (Cd, Pb or Zn) availability compared to the control, but the magnitude of effects depends on each metal and amendment. The addition of dolomite and Na-bentonite reduced significantly the concentrations of Pb and Zn in plants, but this reduction is not enough to produce healthy food or fodder. The application of manure led to a significant increasing of biomass yield comparing with control, even if the extractability of metals in manure treated plots was moderate. The results demonstrate the high potential of Na-bentonite and dolomite to reduce the availability and possible toxicity of heavy metals in contaminated soils but more attention should be paid to the transitory liming effect and metal remobilizing over time.

The potential effects of aeolian processes on the vegetation in a semiarid area: geochemical evidence from plants and soils

Aeolian processes are the key factors controlling the redistribution of nutrient elements in arid and semiarid regions and have a significant effect on plant distribution. However, the potential relationship between aeolian sediments and vegetation is still unknown in a desert environment. By evaluating the concentrations of Ba, Cu, Mg, Mn, Ni, and Zn in the different plants of typical dominant species and co-located soils in the Otindag Desert, northern China, we evaluated the potential effects of aeolian processes on the vegetation. The biological accumulation parameters and the grain size distribution of dune soil in the study area were analyzed by some focused manner. The results showed the following: (1) For the various soils around different species, the order of the relative content of the six elements in the soil by dominant species was Stipa klemenzil, Artemisia frigida, Carex spp., and Caragana microphylla Lam. In this order, the dominant particle size ranges of the soils around these species were 0–63, 63–125, 125–250, and 250–500 μm, respectively. (2) Cu, Mg, Mn, Ni, and Zn in soil tend to be concentrated in the finer particles and Ba tends to be concentrated in the coarser particles. (3) S. klemenzil, A. frigida, and C. microphylla Lam had high absorption rates of Cu and Zn, and the leaves of C. microphylla Lam and A. frigida were significantly enriched in Cu and Mg, and Cu, respectively. According to the above results, we conclude that aeolian processes can potentially influence the absorption of specific nutrients by plants by influencing the texture and element redistribution of soil particles, thereby promoting or hindering the growth of specific vegetation communities.

Effects of ZnSO4 and Zn-EDTA broadcast or banded to soil on Zn bioavailability in wheat (Triticum aestivum L.) and Zn fractions in soil

Human Zn deficiency is prevalent in developing countries, and staple grains are commonly bio-fortified to increase their Zn contents. We measured Zn content, distribution, and bioavailability in calcareous soil and in wheat plants (Triticum aestivum L.) in Shaanxi Province, China, when either an organic Zn-ethylenediaminetetraacetate (Zn-EDTA) or an inorganic zinc sulfate heptahydrate (ZnSO4·7H2O) Zn source was banded below the seedbed or broadcasted into soil. Compared with ZnSO4·7H2O, Zn-EDTA fertilization produced higher Zn concentration and uptake in wheat plants. However, Zn bioavailability in grain remained low, with [phytate]/[Zn] ratio >15 and the resulting estimated dietary total absorbed zinc (TAZ) < 3 mg Zn/d. ZnSO4 banded into soil had little short-term effect on grain Zn concentration but had a high residual effect and promoted the maintenance of a high concentration of the Zn fraction bound to loose organic matter (LOM-Zn) in rhizosphere soil. Both ZnSO4 and Zn-EDTA were more efficient if uniformly mixed through the soil than if banded to soil. Both ZnSO4 and Zn-EDTA had limited effects on Zn bioavailability in wheat plants due to the high rate of Zn fixation in this calcareous soil.

Photosynthetic Apparatus Efficiency of Sida Hermaphrodita Cultivated on Heavy Metals Contaminated Arable Land Under Various Fertilization Regimes

Abstract Contaminated and marginal lands are favourable place for biomass feedstock establishment, especially due to European Union directive 2009/28/EC. This strategy not only cover local demand for energy and heat but also can be valuable in those land phytomanagment. The second-generation perennial energy crop species are the most feasible for such purpose. We studied the impact of two different fertilizer treatments on plant physiological parameters associated with photosynthesis, heavy metals (HMs) and primary macronutrients accumulation in Sida hermaphrodita cultivated on HMs contaminated soil under field conditions. NPK fertilized plants showed the highest values of photosynthetic parameters at the beginning of growing season when compared to control and microbial inoculated plants. However, at the end of the growing season inoculated and control plants showed better photosynthetic performance than NPK treated. NPK fertilizer caused higher Cd and Zn shoot concentrations while microbial inoculation caused higher K and the lowest N and P concentrations in shoot. Due to Cd, Pb and Zn concentrations in plants which should not result in alleviation of photosynthetic apparatus efficiency and biomass production it could be summarize that Sida hermaphrodita is a suitable plant for cultivation on land contaminated with HMs under different fertilization regimes.

Isolation and characterization of potential Zn solubilizing bacteria from soil and its effects on soil Zn release rates, soil available Zn and plant Zn content

In this study, experiments were designed to isolate, characterize and evaluate an array of bacteria isolates for their Zn solubilization potential. Out of the six promising Zn solubilizing bacteria (ZnSB), ZnSB2 (B. megaterium, KY687496) was found to be the most potential strain owing to its enhanced Zn solubilization in vitro. In the quantitative study, the net Zn solubilized by ZnSB2 was significantly higher than those solubilized by the other ZnSB at all days of sampling. Similar effects of ZnSB2 was observed in the soil per se, wherein the rate of release of available Zn by ZnSB2 was markedly higher at all days of incubation (25.6%–40.7% of added Zn), with a peak on the 8th day. Such enhanced rates of Zn release by ZnSB2 were attributed to marked decrease in pH owing to enhanced gluconic acid production. In fact, gluconic acid production by ZnSB2 was 1884.7 ± 413.4 μg mL−1, which was 35.3–69.7% greater than the other shortlisted ZnSB isolates. Further evaluation of ZnSB2 was done in the green house using turmeric as the test crop. ZnSB2 was applied either alone or in combination with chemical Zn (75% and 100% of recommended Zn). The results revealed that soil available Zn level in the treatment with 75% Zn + ZnSB2 (12.69 ± 2.96 mg kg−1) was on par with the level in the treatment with 100% Zn (12.74 ± 2.63 mg kg−1) at 120 days after planting, while at harvest the treatment with 75% Zn + ZnSB2 maintained 65.0% higher available Zn levels than 100% Zn. The positive effect of ZnSB2 was also manifested on rhizome yield, which was at par in the treatments with ZnSB2 + 75% Zn (154.2 g ± 36.0 pot−1) and 100% Zn (177.2 ± 36.7 g pot−1). Besides, the Zn concentration in the rhizome was significantly higher (P < 0.05) in the treatment with ZnSB2 + 75% Zn (40.5 ± 3.5 mg kg−1), which was at par with 100% Zn, but was greater by 98.5% compared to control. The study indicated that ZnSB2 strain was a potential candidate for enhanced Zn dissolution in soil, which would allow reduced inorganic Zn application rates. Nonetheless, in vitro interaction studies (dual culture) suggested that this strain was seriously lacking in disease suppressing traits. But its compatibility with several plant growth promoting rhizobacteria enhanced the possibility of co-inoculation or applying ZnSB2 in a consortium mode especially in condition wherein both soil Zn solubilization and disease suppression becomes imperative.

Yield and nutrient uptake by maize as influenced by phosphorus and zinc application

Bulk soil samples from a long term (45 years) experiment were collected with three treatments (100% N, 50% NPK and 100% NPK) to represent different soil fertility levels for green house study using maize as test crop. To each soil, combinations of 4 levels of P (0, 30, 60 and 120 mg P kg−1) and Zn (0, 6.25, 12.5, 25 mg Zn kg−1) were applied in pots containing 4 kg soil. The effects of different levels of P and Zn were examined on dry matter yield, P and Zn concentrations and their uptake at 45 days after sowing. Soil collected from 100% N plots had the highest dry matter yield and P concentration but the lowest Zn concentration in maize plants. Soil from 100% NPK plots had the highest Zn concentration but lowest dry matter yield. Phosphorus application increased dry matter yield, whereas Zn had minimal effect on dry matter yield. Significant effect of P on Zn concentration was observed, whereas Zn had no effect on P concentration in maize plants.

Phytoremediation assessment of native plants growing on Pb–Zn mine site in Northern Tunisia

Pollution by heavy metals presents an environmental concern, and their toxicity threats soil, water, animals and human health. Phytoremediation can be used as a solution to remediate contaminated soils. The aim of this study was to identify native plants collected from tailings: material of Pb–Zn mine sites of Fedj Lahdoum and Jebel Ressas (two abandoned mines located, respectively, in the northwest of Tunisia and in the south of Tunis City). The tolerance of plant to heavy metals (lead, zinc and cadmium) is evaluated. Soil samples were collected and analyzed for Pb, Zn and Cd concentration. The total soil Pb, Zn and Cd are, respectively, reached 6132 mg kg−1, 11,052 mg kg−1 and it doesn’t exceed 479 mg kg−1 for Cd. The highest content of Zn in plants was detected in shoots of Rumex bucephalophorus (1048 mg kg−1), and the highest Pb concentration was detected in roots of Chrysopogon zizanioides (381 mg kg−1), while for Cd Silene colorata it accumulated the highest content in roots (51 mg kg−1). From all plants, only 12 have a translocation factor for Pb which is higher than one. Among all plants, only 17 have a translocation factor that is higher than one for Zn, while for Cd only 13 plants indicate TF > 1. As for the biological absorption coefficient, all samples indicate a rate which is lower than one. These plants can be primarily hyper accumulators and useful in remediation of lead- and zinc-contaminated soils after further biochemistry researches in mechanism of accumulation and translocation of heavy metals in plants.

Accumulation of Heavy Metals in Soil Growing for Red Pepper (Capsicum annuum) with using Lime Bordeaux and Lime Sulphur Mixture

Lime bordeaux mixture (LBM) and lime sulfur mixture (LSM) are representative environmental friendly organic materials for prevention of insect pests in South Korea. Recently, those have been widely used as an alternative for chemical pesticides in eco-friendly farms. However, South Korea has not established even recommendation of LBM and LSM considering the stability of heavy metals in soil. The aim of this study was to evaluate the accumulation of hazardous heavy metals in soil and plant with long-term application of LBM and LSM. Firstly, we investigated the amount of LBM and LSM used per year in several eco-friendly farms to determine a standard application rate of both materials. The pepper plant was grown on the pot in greenhouse for 14 weeks. Both materials were applied at 0, 1, 3, and 9 times of standard application rates (2.56 and 1.28 L ha-1 of LBM and LSM per year, respectively). Dry matter yield of pepper and heavy metals (As, Cd, Cu, Hg, Ni, Pb, and Zn) concentration in soil and pepper plant were measured after 14 weeks. Yield of pepper plant did not significantly chang with up to application rate of 1 times, thereafter it markedly decreased with more than 3 times. With increasing LBM and LSM application, the concentration of Cu and Zn in soil significantly increased. Especially, Zn concentration in pepper significantly increased with increasing application rates of both materials. This might resulted in significant decrease in dry matter yield of pepper. The concentrations of those heavy metals in soil did not exceed safety levels (150 mg kg-1 for Cu and 300 mg kg-1 for Zn) established by the Korean Soil Environmental Conservation Act as well as concentration of heavy metals in pepper plant by Korean Ministry of Food and Drug Safety. However, particular attention should be paid for heavy metal safety and crop productivity when using LBM and LSM in the organic farm. Concentration of heavy metals in soil amended with different rate of Bordeaux and Sulphur mixtures at harvest time. †Criteria value: Maximum permissible concentration of heavy metal in soil established by Korean Soil Conservation Act.‡Average value: Average concentration of heavy metals in Korean arable soils.§tr: trace.

Effect of calcium bentonite on Zn and Cu mobility and their accumulation in vegetable growth in soil amended with compost during consecutive planting.

In this study, greenhouse pot experiment was carried out to investigate the Cu and Zn mobility and their accumulations in pakchoi (Brassica chinensis L.) and Chinese cabbage (Brassica rapachinensis L.) growth in Ca-bentonite-pig manure co-compost (CBC)-soil system during three consecutive planting. Five composts (0, 2.5, 5, 7.5, and 10% Ca-bentonite-pig manure co-composts) amended soil with 5% (w/w) application rate and compared to control without any additive. The results showed that the addition of CBC increased the biomass and chlorophyll content of pakchoi, and the maximum overall yield was found in 7.5% CBC treatment (12.89±0.25g), while when compared with the 0% CBC (15.89±0.52g) treatment, the Ca-bentonite amendment slightly decreased the Chinese cabbage yield (14.65±0.11-15.41±1.97g). Additionally, compared to the 0% CBC treatment (11.81±0.57-25.75±0.89mg/kg), the Ca-bentonite amendments showed a positive effect on restraining the diethylene triamine penta-acetic acid Zn mobilization (4.43±0.41-12.48±2.54mg/kg) in pakchoi and Chinese cabbage; beside this, no obvious effect was observed on DTPA-Cu. Furthermore, there were great potential impacts for plant-available Zn in Ca-bentonite amended treatments during the consecutive planting, which decreased the content of Zn in plants. DTPA extraction results showed significantly higher Cu and Zn contents in compost-soil mixture, but its availability for grown plant was not confirmed during the consecutive planting, because of the consecutive decrease heavy metals contents in crops. Overall, the Ca-bentonite could be a useful additive for restricting the heavy metal mobility and increase the pakchoi yield.

Heavy Metal and Phosphorus Contents of Jew's Mallow (Corchorus olitorius L.) Plants Grown on Soil Amended with Phosphate, Bio and Organic Fertilizers

This study was conducted to assess the impact of different chemical, organic and bio fertilizers on growth, phosphorus and heavy metal (Zn, Cd, Co, Cu and Ni) contents of Jew's mallow (Corchorus olitorius L.) plants. Pot and field experiments were carried out in the screen house and experimental farm, Faculty of Agriculture, South Valley University, Egypt in the summer season of 2013 and 2014, respectively. The experimental treatments included rock phosphate, superphosphate and triple superphosphate fertilizers singly or in combination with phosphate dissolving bacteria (PDB) and/or filter mud cake (FMC) as biological and organic amendment to the soil. They had a completely randomized design and complete block randomized design with three replications for pot and field experiment, respectively. The results of both experiments showed that, although the second and third cuts gave greater plant growth than that of the first cut, only the first cut of the plants received rock phosphate fertilizer either alone or in a combination with PDB and FMC or their mixture contained the lowest level of heavy metals. The results indicated that, only in the first cut with plants receiving rock phosphate fertilizer either alone or combined with PDB, FMC and PDB+FMC recorded the lowest Zn content values of 45.0, 56.0, 64.0 and 94.0 mg / kg, respectively which were below permissible limit, while the second and third cut Zn concentration in plants with different combination treatments was higher than the permissible levels. Also, rock phosphate treatment alone or with PDB in the first cut showed lowest plant Ni content (10 mg/kg) which on the border of the permissible level. The cobalt level in C. olitorius plants that received all phosphate fertilizer types (ranged from 7.0 to 16 mg/Kg) were below the permissible limit. The Cu level in investigated plants received all phosphate fertilizer types with different combination treatments with the three cuts were within the acceptable range. Also the results showed that plants grown on the soil amended with natural rock phosphate alone or in combination with phosphate dissolving bacteria recorded lowest Cd values. It is recommended to use the natural rock phosphate in combination with phosphate dissolving bacteria for growing Jew’s mallow plants instead of chemical phosphate fertilizers and the plants should be harvested by pulling the whole plant including roots from the soil after 40 days from planting to avoid high heavy metal uptake by the plants of the second and third cuts which had a possible health impacts.

Remediation of Arsenic Toxicity in the Soil-Plant System by Using Zinc Fertilizers

Availability of soil arsenic (As) and plant As at various levels of zinc (Zn) and As applications were examined. A pot-culture experiment with a leafy vegetable, Kalmi (Ipomoea aquatica), on an Inceptisols, was conducted where As was applied with irrigation water at the rates of 0 mg/L (As control), 0.5 mg/L, 1 mg/L and 2 mg/L and Zn was added to the soil as ZnCl2 solution at the rate of 0 mg/L (Zn control), 1 mg/L, 2 mg/L and 3 mg/L during pot preparation. The experiment was conducted in triplicates for 45 days till the plants were grown to maturity. At the end of the experiment the remedial effect of Zn on As toxicity was examined and as such, yield parameters, As and Zn accumulation in Kalmi plants, residual concentrations of As and Zn in soils and plants were measured. It appeared from the present study that there exists an antagonistic relationship between Zn and As i.e., Zn in soils was found to reduce As availability in soils as well as its accumulation in plants, particularly at an elevated application rate of 3 mg/L Zn. The findings could be used as a strategy to mitigate arsenic toxicity in As contaminated soils.

Co-Granulated and Blended Zinc Fertilizer Comparison for Corn and Soybean

A new co-granulated formulation of monoammonium phosphate (MAP) including S and Zn could allow for more uniform nutrient distribution. A six site-year study evaluated the effects of blended phosphorus (P) sources [MAP and diammonium phosphate (DAP)] and zinc amounts (0, 2.2, and 5.6 kg Zn ha-1) compared to co-granulated fertilizer, MicroEssentials® Sulfur-10 (MES10™) (12-40-0-10S) and MicroEssentials Sulfur and Zinc (MESZ™) (12-40-0-10S-1Zn), on corn and soybean response. Fertilizers were broadcast applied for corn and the carry-over effect on soybean was determined. Ear leaf P, S, and Zn concentrations at Novelty in 2013 and 2014 were within the sufficiency range regardless of treatment, even though initial soil test values were low-medium. Yields were similar to the N only control for all site-years except at Novelty in 2013, where MAP+ZnSO4 at 2.2 kg Zn ha-1, MAP+Super Zn at 5.5 kg Zn ha-1, and DAP+AMS were 540 to 570 kg/ha greater. The amount of Zn fertilizer (2.2 vs. 5.6 kg Zn ha-1) also showed no significant effect on yield. Applications of P or Zn generally increased their concentrations in post-harvest soil samples. Fertilizer applied for corn indicated some differences in soybean plant nutrient concentrations, but it had no effect on total plant nutrient uptake, grain yield or quality. At Novelty, soybean plant Zn concentration was greater at 5.6 kg Zn ha-1 compared to 2.2 kg Zn ha-1, while Albany showed an increase in whole soybean plant Zn concentration with SuperZn compared to ZnSO4. Carry-over fertilizer from corn showed limited effects on soybean response the following year.

Effects of synthetic Zn chelates on flax response and soil Zn status

Throughout the world, flax (Linum usitatissimum L.) is often grown in Zn-deficient soils, but appropriate fertilizer management can optimize both crop yield and micronutrient content. A greenhouse experiment was conducted on Typic Haploxeralf (pH 6.1) and Typic Calcixerept (pH 8.1) soils to study the relative efficiency of chelated Zn using two application rates of three different Zn sources [Zn-EDDHSA, ethylenediamine-di-(2-hydroxy-5-sulfophenylacetate of Zn); Zn-HEDTA, N-2-hydroxyethyl-ethylenediaminetriacetate of Zn; and Zn-EDTA, ethylenediaminetetraacetate of Zn]. Dry matter /DM) yield, Zn concentration, chlorophyll content, crude fiber and tensile properties were monitored and the soil-Zn status (available-Zn, Zn-fractions and total-Zn) was assessed. Zinc chelate applications increased the most labile forms of Zn in soils and Zn concentrations in plants. The low rate of Zn generally had a beneficial effect on DM yield and tensile properties. The exception was Zn-EDTA in the weakly acidic soil, where the highest Zn concentrations were observed in leaves and whole shoots; this coincided with the largest concentrations of labile Zn in soil. The most efficient fertilizers were Zn-EDDHSA (in both soils) and Zn-EDTA (in the calcareous soil). The relatively large amounts of labile and available Zn present in both of the soils fertilized with Zn-EDTA points to the applying this chelate at lower rate than 5 mg Zn/kg; this should, in turn, reduce the cost of Zn fertilization and minimize environmental pollution risk.

Amelioration of iron mine soils with biosolids: Effects on plant tissue metal content and earthworms.

The achievement of environmentally sound and economically feasible disposal strategies for biosolids is a major issue in the wastewater treatment industry around the world, including Swaziland. Currently, an iron ore mine site, which is located within a wildlife sanctuary, is being considered as a suitable place where controlled disposal of biosolids may be practiced. Therefore, this study was conducted to investigate the effects of urban biosolids on iron mine soils with regard to plant metal content and ecotoxicological effects on earthworms. This was done through chemical analysis of plants grown in biosolid-amended mine soil. Earthworm behaviour, reproduction and bioaccumulation tests were also conducted on biosolid-amended mine soil. According to the results obtained, the use of biosolids led to creation of soil conditions that were generally favourable to earthworms. However, plants were found to have accumulated Zn up to 346mgkg-1 (in shoots) and 462mgkg-1 (in roots). This was more than double the normal Zn content of plants. It was concluded that while biosolids can be beneficial to mine soils and earthworms, they can also lead to elevated metal content in plant tissues, which might be a concern to plant-dependant wildlife species. Nonetheless, it was not possible to satisfactorily estimate risks to forage quality since animal feeding tests with hyperaccumulator plants have not been reported. Quite possibly, there may be no cause for alarm since the uptake of metals from soil is greater in plants grown in pots in the greenhouse than from the same soil in the field since pot studies fail to mimic field conditions where the soil is heterogeneous and where the root system possesses a complex topology. It was thought that further field trials might assist in arriving at more satisfactory conclusions.

Soil variables that determine lead accumulation in Bidens pilosa L. and Tagetes minuta L. growing in polluted soils

Toxic metal soil pollution is one of the most serious environmental problems, with phytoextraction being an ecological and inexpensive potential solution to recuperate soil functionality. This emergent technology has produced good results for many elements, but phytoextraction has not been as successful for lead as for other pollutants. This research aimed to evaluate several factors that could be determinant on Pb uptake by the accumulator plants Bidens pilosa and Tagetes minuta. Topsoils (bulk and ryzospheric) and plants were collected around a former Pb smelter, and sequential extractions of Pb, Cu and Zn, organic matter content, electrical conductivity, pH, and texture were measured in soils. Also, bacterial diversity in soil was determined by the denaturing gradient gel electrophoresis (DGGE) technique. The Pb, Cu, and Zn concentrations in soil extractions and plants (leaves, stem, and root) were quantified by T-XRF in Synchrotron, Brazil. Our results demonstrated that Pb uptake from polluted soils and translocation to aerial tissues by two Asteraceae species are related not only to the traditional soil parameters, but even more importantly to the Zn and Cu concentrations in plant and soils. In addition, the soil bacterial biodiversity also affects the Pb uptake by plants. In this study, we propose the total translocation factor (TTF) to evaluate the phytoextraction efficiency, which is given by the ratio of total extraction of Pb in aerial organs and roots, instead of using the Pb concentrations alone.

Differential cadmium stress tolerance in wheat genotypes under mycorrhizal association

ABSTRACTArbuscular mycorrhizal (AM) fungi display efficient association with the land plants and is known to protect plants against various abiotic stresses including heavy metal stress. This work reports the synergistic effects of natural genotypic variation and AM association in cadmium (Cd) stress alleviation. Two genotypes of wheat viz. RAJ 4161 (resistant) and PBW 343 (sensitive) were subjected to different concentrations of Cd (0, 100, 200 and 300 mg Cd kg−1 soil) for 30 days. Cd application resulted in increased lipid peroxidation and decreased plant growth. However, AM inoculated RAJ 4161 displayed significantly higher ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) activity and calcium (Ca), iron (Fe)and zinc (Zn) concentration in plants. The coordination of increased antioxidant activity and high nutrient content in RAJ 4161 indicated better protective mechanism as compared to PBW 343.

Can arbuscular mycorrhizal fungi improve competitive ability of dill+common bean intercrops against weeds?

Abstract Competition for soil resources plays a key role in the crop yield of intercropping systems. There is a lack of knowledge on the main factors involved in competitive interactions between crops and weeds for nutrients uptake. Hence, the purpose of this work was to compare the effects of arbuscular mycorrhial fungi ( Funneliformis mosseae ) colonization in interspecific competitive relations and its effect on nutrients uptake and weed control in dill and common bean intercropping. Two field experiments were carried out with factorial arrangements based on randomized complete block design with three replications during 2013–2014. The factors were cropping systems including a) common bean ( Phaseolus vulgaris L.) sole cropping (40 plants m −2 ), b) dill ( Anethum graveolens L.) sole cropping at different densities (25, 50 and 75 plants m −2 ) and c) the additive intercropping of dill + common bean (25 + 40, 50 + 40 and 75 + 40 plants m −2 ). All these treatments were applied with (+AM) or without (-AM) arbuscular mycorrhiza colonization. In both cropping systems, inoculation with F. mosseae increased the P, K, Fe and Zn concentrations of dill plants by 40, 524, 57 and 1.0 μg kg −1 DW, respectively. Intercropping increased Mn concentration in common bean (4.0 μg kg −1 DW) and dill (3.0 μg kg −1 DW), and also seed yields of both crops (198 g m −2 and161 g m −2 , respectively). AM colonization improved seed yields of dill and common bean by 169 and 177 g m −2 in 2013 and 2014, respectively. Moreover, AM application enhanced competitive ability of dill + common bean intercrops against weeds at different intercropping systems. Intercropping significantly changed weed density compared to sole cropping, as weed density was decreased in the dill + common bean intercropping. Diversity (H), Evenness (E) and richness of weed species of weeds for intercrops were higher than those for sole crops.