Impact of liming on utilization of 59Fe‐chelates by lettuce (Lactuca sativa L.)

A pot experiment was conducted to determine the utilization of iron (Fe) by lettuce (Lactuca sativa L. cv. Australian gelber). Iron was applied as ⁵⁹Fe in inorganic and chelated form, particularly biodegradable chelate, ⁵⁹Fe‐EDDS. Two stereoisomeric forms of ethylenediaminedisuccinate: [S,S]‐EDDS and a mixture of EDDS containing 25% [S,S]‐EDDS, 25% [R,R]‐EDDS, and 50% [S/R]/[R/S]‐EDDS, ethylenediaminetetraaceticacid (EDTA) and ethylenediimino bis(2‐hydroxyphenyl)acetic acid (EDDHA) were used as ligands. Lettuce was grown in unlimed and limed quartz sand with nitrate as the sole source of nitrogen. Liming decreased lettuce yields but had no effect on Fe concentrations, indicating that Fe concentrations were a poor indicator of Fe bioavailability within the plant. In unlimed sand, utilization of ⁵⁹Fe from all ⁵⁹Fe‐chelates was on the same level (2.8%–3.6%). In limed sand, only ⁵⁹Fe‐EDDHA maintained the ⁵⁹Fe utilization on a level (3%) comparable to that in unlimed sand. Although the utilization of ⁵⁹Fe from the other chelates decreased to 0.6%–1.1% after liming, Fe concentrations were not affected due to the increased uptake of indigenous Fe. The most biodegradable form of EDDS, namely ⁵⁹Fe‐EDDS(S,S), provided ⁵⁹Fe for lettuce as efficiently as the mixture of ⁵⁹Fe‐EDDS stereoisomers and the ⁵⁹Fe‐EDTA. Utilization of ⁵⁹Fe in inorganic form was 0.5% and 0.03% in unlimed and limed sand, respectively. This study shows that biodegradable ligands are able to serve as chelators to sustain Fe availability in calcareous environments. They may be of use especially in drip irrigation, where ligand accumulations may pose a threat to groundwater quality.     

INFLUENCE OF IRON-CHELATES ON TRACE ELEMENT UPTAKE FROM TWO CALCAREOUS SOILS AND THE ACTIVITY OF OXYGEN-SCAVENGING ENZYMES IN LETTUCE

A pot experiment was carried out to determine the ability of lettuce (Lactuca sativa cv. ‘Waldmann's dark green’) to acquire iron (Fe) from Fe-ethylenediaminedisuccinic acid [EDDS, both as an isomeric mixture, EDDS(mix), and (S,S)-EDDS], Fe-ethylenediaminetetraacetic acid (EDTA) and Fe-ethylenediimonobis(2-hydroxyphenyl)acetic acid (EDDHA) in two calcareous soils and consequent effect on the activity of reactive oxygen species scavenging enzymes. Probably due to the rapid biodegradation of [S,S]-EDDS, EDDS(mix) provided Fe to lettuce more efficiently. Iron-EDDS(mix) and Fe-EDDHA were equally efficient in increasing Fe concentration in lettuce. The activity of superoxide dismutase (SOD) was not affected by Fe deficiency and the activity of copper (Cu) and zinc (Zn) containing SOD (Cu/ZnSOD) was dependent on lettuce Zn concentration. Ascorbate peroxidase and guaiacol peroxidase activities were increased by Fe-EDDHA, probably due to the steady supply of Fe. Physiologically active Fe pool for lettuce was equally provided by Fe-EDDS(mix) and Fe-EDTA.     

Comparison of iron chelates and complexes supplied as foliar sprays and in nutrient solution to correct iron chlorosis of soybean

The application of synthetic chelates is the most efficient remedy for correcting iron (Fe) chlorosis. However, chelates are usually expensive and nondegradable products. Recently, new degradable chelates have been proposed for their use as Fe fertilizers. Also, Fe complexes cheaper than synthetic chelates and derived from natural products are also used to correct Fe deficiencies. Fifteen products, including five different synthetic chelates (Fe‐EDDS, Fe‐IDHA, and three Fe‐EDTA formulations) and ten natural complexes (humates, lignosulfonates, amino acids, glycoproteins, polyamines, citrate, and gluconate), have been compared when applied at low concentration to soybean (Glycine max L.) chlorotic plants grown in hydroponics under controlled conditions. In the first experiment, Fe compounds were applied to the nutrient solution, while in the second trial, Fe was foliar‐supplied. Dry matter, Fe concentration in shoots and roots, and SPAD values were used to evaluate the effectiveness of the Fe in the different products. In the nutrient‐solution experiment, synthetic chelates provided better plant growth, Fe concentration, and SPAD values than complexes. Among the Fe complexes, transferrin generally provided good plant responses, similar to those obtained with synthetic chelates. After foliar application, the highest regreening was observed for plants treated with synthetic chelates and amino acid complexes, but the translocation to roots only occurred for Fe lignosulfonate. Fe‐EDDS and Fe‐EDTA performed in a similar way when applied in nutrient solution or as foliar sprays.     

Partial replacement of Fe(o,o‐EDDHA) by humic substances for Fe nutrition and fruit quality of citrus

The most widely used Iron (Fe) fertilizer in calcareous soils is the synthetic chelate Fe(o,o‐EDDHA). However, humic substances are occasionally combined with Fe chelates in drip irrigation systems in order to lower costs. We investigated the effect of various mixtures of Fe(o,o‐EDDHA) and a commercially available humic substance on Fe availability in a calcareous soil from Murcia, Spain (in vitro experiment) and on leaf Fe content and fruit‐quality attributes of Citrus macrophylla (field experiment). In the in vitro experiment, a calcareous soil was incubated for 15 d with solutions of sole Fe(o,o‐EDDHA) and humic substance and of a mixture of humic substance and Fe(o,o‐EDDHA) to determine the dynamics of available Fe. While the mixture did not significantly increase the available soil Fe, it did decrease the rate of Fe retention in the surface soil compared to sole Fe(o,o‐EDDHA). In the field experiment, the substitution in the application solution of 67% of Fe(o,o‐EDDHA) by commercial humic substance increased leaf P in lemon trees from 0.19% with sole Fe(o,o‐EDDHA) to 0.30% and leaf Fe from 94 mg kg^–1 to 115 mg kg^–1. Some quality parameters like vitamin C content and peel thickness were also improved with a partial substitution of Fe(o,o‐EDDHA) by humic substances. We conclude that a partial substitution of commercial Fe chelates by humic substance can improve crop Fe uptake and may thus be economically attractive. The underlying physiological mechanisms and ecological implications require further studies.     

Prevention of Iron‐Deficiency Induced Chlorosis in Kiwifruit (Actinidia deliciosa) Through Soil Application of Synthetic Vivianite in a Calcareous Soil

Abstract

In this study we have tested the hypothesis that lime‐induced Fe deficiency chlorosis of kiwifruit may be prevented by the application of a synthetic iron(II)‐phosphate analogous to the mineral vivianite [(Fe₃(PO₄)₂·8H₂O)]. Two experiments, under greenhouse and field conditions, were performed. In the greenhouse, 1‐year old micropropagated plants (Actinidia deliciosa, cv. Hayward), grown in 3‐L pots on a calcareous soil, were treated in early autumn with soil‐applied: (1) synthetic vivianite (1.35 g plant^?1) and (2) Fe‐EDDHA (24 mg Fe plant^?1). The synthetic vivianite suspension, prepared by dissolving ferrous sulfate and mono‐ammonium phosphate, was injected into the soil as a sole application whereas the Fe‐EDDHA solution was applied four times at weekly intervals. The field experiment was conducted in a mature drip‐irrigated kiwifruit orchard located on a calcareous soil in the Eastern Po Valley (Italy). Treatments were performed in early autumn by injecting synthetic vivianite (1.8 kg tree^?1) and Fe‐EDDHA (600 mg Fe tree^?1) into four holes in the soil around each tree, at a depth of 25–30 cm. The Fe‐chelate application was repeated at the same rate in the following spring. Untreated (control) plants were used in both experiments. Autumn‐applied Fe fertilisers significantly prevented development of Fe chlorosis under greenhouse conditions whereas in the field only vivianite was effective. In conclusion, these 1‐year results show that vivianite represents an effective alternative to soil‐applied Fe chelates for preventing Fe chlorosis in kiwifruit orchards.     

Glutathione foliar fertilisation prevents lime‐induced iron chlorosis in soil grown Medicago scutellata

It has been proposed that glutathione can relieve the effects of Fe deficiency. This study tested the effects of glutathione foliar treatments to prevent Fe chlorosis, using as positive controls soil and foliar Fe fertilisation. Medicago scutellata plants were grown in soil (5.7% CaCO₃) supplemented or not with 4 and 8% CaCO₃. Two Fe(III)‐EDDHA soil treatments (5 and 10 mg Fe kg^?1), and three foliar treatments (three applications each of 2.14 mM Fe(III)‐EDDHA, 1 mM glutathione, and the previous two combined) were applied. Measurements include leaf chlorophyll and Fe concentrations, biomass, leaf enzymatic and non‐enzymatic antioxidant systems and carboxylates. The addition of CaCO₃ caused typical Fe deficiency symptoms, including changes in chlorophyll, Fe, antioxidant systems and carboxylates, which were prevented by soil and foliar Fe fertilisation. The foliar treatment with glutathione also led to higher chlorophyll, leaf extractable Fe and root Fe, as well as decreases in some antioxidant systems, whereas leaf Fe concentrations decreased. The combined foliar application of glutathione and Fe was even more efficient in preventing chlorosis. Including glutathione in foliar fertilisation programs should be considered as an option for Fe chlorosis prevention, especially when relatively large leaf total Fe concentrations occur in the so called chlorosis paradox.     

Interaction of iron chelates with several soil materials and with a soil standard

Frequently the effectiveness of iron (Fe) chelates is low because they can be retained or destroyed by soil materials. The high cost of these Fe fertilizers makes it necessary to study soil material reaction with Fe chelates. Commercial Fe chelates with EDTA, EDDHA, and EDDHMA as ligands and their standards, prepared in the laboratory, were shaken for one hour with various soil materials [amorphous Fe(III) oxide, acid peat, calcium (Ca)‐montmorillonite and calcium carbonate (CaCO₃)] and with a soil standard made in the laboratory. After agitation, the chelate‐soil mixtures were filtered and the micronutrients and chelated Fe that remained in solution were determined. Among the soil materials used, amorphous Fe(III) oxide and acid peat had the greatest affect on the amount of chelated Fe remaining in solution. The type of chelating agent was the next major factor that affected the availability of soluble Fe following reaction with the soil materials. Another factor was the commercial formulation of the Fe chelates. The chelates comprised of EDDHA or EDDHMA maintained the highest percentages of chelated Fe in solution after interaction with the solid phases, except for the acid peat. The last soil material, acid peat, retained more chelated Fe for the Fe chelates with EDDHA or EDDHMA than with EDTA as the chelating agent. The commercial Fe‐EDDHA chelates had greater losses of chelated Fe than their standard after interaction with all the solid phases. The commercial Fe‐EDDHA chelate (Sequestrene) and the commercial Fe‐EDDHMA chelate (Hampirón) solubilized the highest amount of copper (Cu) from soil standard. This was attributed to the presence of by‐products in the commercial formulations since the Fe‐EDDHA standard did not have Cu in solution after the interaction. Therefore, the commercial Fe chelate by‐products are able to form Cu‐complexes which could affect chelated Fe and its availability to plants.     

Interaction of Different Iron Chelates with an Alkaline and Calcareous Soil: A Complementary Methodology to Evaluate the Performance of Iron Compounds in the Correction of Iron Chlorosis

Abstract

A great number of studies have shown that the stability of iron chelates as a function of pH is not the unique parameter that must be considered in order to evaluate the potential effectiveness of Fe‐chelates to correct iron chlorosis in plants cultivated in alkaline and calcareous soils. In fact, other factors, such as soil sorption on soil components or the competition among Fe and other metallic cations for the chelating agent in soil solution, have a considerable influence on the capacity of iron chelates to maintain iron in soil solution available to plants. In this context, the aim of this work is to study the variation in concentration of the main iron chelates employed by farmers under field conditions—Fe‐EDDHA (HA), Fe‐EDDHMA (MA), Fe‐EDDHSA (SA), Fe‐EDDCHA (CA), Fe‐EDTA (EDTA), and Fe‐DTPA (DTPA)—in the soil solution of a calcareous soil over time. To this end, soil incubations were carried out using a soil:Fe solution ratio corresponding to soil field capacity, at a temperature of 23°C. The soil used in the experiments was a calcareous soil with a very low organic matter content. The variation in concentration of Fe and Fe‐chelates in soil solution over time were obtained by measuring the evolution in soil solution of both the concentration of total Fe (measured by AAS), and the concentration of the ortho‐ortho isomers for Fe‐EDDHA and analogs or chelated Fe for Fe‐EDTA and Fe‐DTPA (measured by HPLC). The following chelate samples were used: a HA standard prepared in the laboratory and samples of HA, MA, SA, CA, Fe‐EDTA, and Fe‐DTPA obtained from commercial formulations present in the market. The percentage of iron chelated as ortho‐ortho isomers for HAs was: HA standard (100%); HA (51.78%); MA (60.06%); SA (22.50%); and CA (27.28%). In the case of Fe‐EDTA and Fe‐DTPA the percentages of chelated iron were 96.09 and 99.12, respectively. Results show that it is possible to classify the potential effectiveness of the different types of iron chelates used in our experiments as a function of two practical approaches: (i) considering the variation of total iron in soil solution over time, MA is the best performing product, followed by HA, CA, SA, DTPA, EDTA, and ferrous sulfate in the order listed and (ii) considering the capacity of the different iron chelates to maintain the fraction of chelated iron (ortho‐ortho isomers for HA, MA, SA, and CA and total chelated iron for EDTA and DTPA) in soil solution, the order is: SA > CA > HA > MA > EDTA ≈ DTPA. This result, that is related to the nature of the chelate and does not depend on the degree of chelated Fe in the products, indicates that SA and CA might be very efficient products to correct iron chlorosis. Finally, our results also indicate the suitability of this soil incubation methodology to evaluate the potential efficiency of iron compounds to correct iron chlorosis.     

Iron fertilizers applied to calcareous soil on the growth of peanut in a pot experiment

A greenhouse pot experiment was conducted with peanuts (Arachis hypogaea L., Fabceae) to evaluate iron compound fertilizers for improving within-plant iron content and correcting chlorosis caused by iron deficiency. Peanuts were planted in containers with calcareous soil fertilized with three different granular iron nitrogen, phosphorus and potassium (NPK) fertilizers (ferrous sulphate (FeSO₄)–NPK, Fe–ethylendiamine di (o-hydroxyphenylacetic) (EDDHA)–NPK and Fe–citrate–NPK). Iron nutrition, plant biomass, seed yield and quality of peanuts were significantly affected by the application of Fe–citrate–NPK and Fe–EDDHA–NPK to the soil. Iron concentrations in tissues were significantly greater for plants grown with Fe–citrate–NPK and Fe–EDDHA–NPK. The active iron concentration in the youngest leaves of peanuts was linearly related to the leaf chlorophyll (via soil and plant analyzer development measurements) recorded 50 and 80 days after planting. However, no significant differences between Fe–citrate–NPK and Fe–EDDHA–NPK were observed. Despite the large amount of total iron bound and dry matter, FeSO₄–NPK was less effective than Fe–citrate–NPK and Fe–EDDHA–NPK to improve iron uptake. The results showed that application of Fe–citrate–NPK was as effective as application of Fe–EDDHA–NPK in remediating leaf iron chlorosis in peanut pot-grown in calcareous soil. The study suggested that Fe–citrate–NPK should be considered as a potential tool for correcting peanut iron deficiency in calcareous soil.     

Effectiveness of iron chelates and FeSO4 for correcting iron chlorosis of peanut on calcareous soils

The effectivenness of different Fe chelates to correct lime induced chlorosis of peanut (Arachis hypogaea) was tested on calcareous soils in Cyprus. Among the chelates tested, Fe‐DTPA and Fe‐EDTA were less effective than Fe‐EDDHA. In one experiment. Fe‐EDDHMA Was less effective while in another experiment was equally effective compared to Fe‐EDDHA . Three different commercial chelates of the form Fe‐EDDHA were equally effective in correcting iron chlorosis. The stability of the Fe‐EDDHA chelate in the soil does not affect its efficiency in curing chlorosis of peanut due to the short growing season for this crop. Ferrous sulfate applied without an acidifying soil amendment was not effective to correct iron chlorosis of peanut.     

Effects of the Frequency of Iron Chelate Supply by Fertigation on Iron Chlorosis in Citrus

Abstract

A field experiment was carried out in a drip‐irrigated orchard of Clementine (Citrus clementina Ort. ex. Tan) grafted on Troyer citrange (C. sinensis × Poncirus trifoliata) rootstock located in the Valencian Citrus area (Spain). The trees received a single iron (Fe) EDDHA (ethylene diamine diorthohydroxyphenyl acetate) rate (3 g Fe tree^?1) supplied in different application frequencies from April to September (8‐, 4‐, 2‐, or 1‐week intervals). Leaf chlorophyll (Chl) concentrations were estimated every month by using an SPAD‐502 meter. The foliar contents of Fe were also evaluated with time. Mineral composition of leaves, total Chl concentration, yield, and fruit quality were also evaluated at the end of the assay. SPAD readings, Chl, N, K, Mg, Fe, and Mn concentration in leaves increased as a result of Fe application. The concentration of Zn, however, significantly decreased in comparison to the control trees. Iron treatment increased yield and some of the fruit quality parameters, like total juice, sugar, and acid contents. Iron application frequency had not a consistent effect on the concentrations of macro and micronutrients in leaves, yield, and fruit quality. The highest values of SPAD readings and the leaf Chl content were obtained when Fe was applied at 4‐week intervals along the year. These results suggest that soil Fe‐EDDHA application with a moderate frequency could be recommended to the Citrus farmers in the area for a more rational Fe application along the growth cycle in Citrus orchards.     

Response of Gemlik Olive Trees to Soil and Foliar Treatments of Iron in Combination with Zinc and Boron

This research was conducted to determine the effectiveness of various treatments in correction of single deficiency of iron (Fe) and multiple deficiencies of Fe, zinc (Zn), and boron (B) in an olive cultivar (Gemlik) in the southeastern Marmara region of Turkey. This study was consisted of four field experiments, which included control, soil and foliar applications of Fe alone, and combinations with Zn and B. Soil applications of the compounds were only performed in the first year of the experiments to estimate residual effect of soil applications in the following year. Foliar applications were sprayed onto leaves two and four times at two doses in consecutive years. Soil application of iron sulfate did not increase Fe concentrations in the both leaves and fruits. Foliar applications of iron sulfate considerably elevated leaf total and active Fe concentrations, but the effect of the foliar applications on fruit Fe concentrations was small. Two foliar applications of iron in each season seemed to be appropriate treatment in the all experiments, as well. To maintain sufficient Fe concentrations, especially in the newly developing tissues of olive trees, foliar application of Fe should be conducted at least four times at the lowest dose as performed in the experiments. Foliar applications of double and triple combinations of iron sulfate with zinc sulfate and borax increased significantly B and Zn concentrations in the trees, as well.     

Iron treatment of lime‐induced chlorosis: Implications for chlorophyll,Fe2 +, Fe3 + and K+ in leaves 1

This study addressed some complementary aspects related to plant Fe nutrition. A field and a greenhouse experiment were conducted to monitor changes in chlorophyll, Fe³⁺, Fe²⁺, Ca²⁺ and K⁺ along with the progressive evolution of lime‐induced chlorosis, and following soil (Fe‐EDDHA, Fe‐EDTA, Fe‐DTPA, DTPA) and foliar (Fe‐EDDHA, FeSO₄, “Fe‐Metalosate") treatments, in a chlorosis‐susceptible ornamental plant, Hydrangea macrophylla, over a year's growing period. Though soil Fe‐EDDHA was the most effective compound in alleviating chlorosis symptoms, it became less so with time and was only partly effective as a foliar spray. Leaf analysis showed that as chlorosis intensified and chlorophyll content decreased, phenanthroline ‐ Fe (Fe²⁺) decreased with corresponding increases in total iron (Fe³⁺) and K⁺ concentrations. The reliability of these chlorosis‐indicators was confirmed as the reverse changes occurred upon chlorosis plant recovery.     

Fe Chelates for Remediation of Fe Chlorosis in Strategy I Plants

Abstract

Iron chlorosis is a mineral disorder due to low Fe in the soil solution and the impaired plant uptake mechanism. These effects increased with high pH and bicarbonate buffer. The solution to Fe chlorosis should be made by either improving the Fe uptake mechanism or increasing the amount of Fe in the soil solution. Among Fe fertilizers, only the most stable chelates (EDDHA and analogous) are able to maintain Fe in the soil solution and transport it to the plant root. In commercial products with the same chelating agent, the efficacy depends on the purity and the presence of subproducts with complexing activity, that can be determined by appropriate analytical methods such as HPLC. In commercial products declaring 6% as Fe‐EDDHA, purity varied from 0.5% to 3.5% before 1999, but in 2002 products ranging 3–5.4% chelated Fe are common in the Spanish market. Fe‐o,p‐EDDHA, as a synthesis by‐product with unknown efficacy, is present in all Fe‐EDDHA formulations. Commercial Fe‐EDDHMA products also contain methyl positional isomers. Fe‐EDDHSA synthesis produces condensation products with similar chelating capacity to the Fe‐EDDHSA monomer that can account for more than 50% of the chelated iron in the commercial products. Chelates with different molecules should be compared for their efficacy considering firstly their ability to maintain Fe in solution and secondly their capacity to release iron to the roots. Accepting the turnover hypothesis, their efficacy is also dependent thirdly on the ability of the chelating agent to form the chelate using native iron from the soil. The 1st and 3rd points are related to the chemical stability of the chelate, while plants make better use of iron from the less stable chelates. Plant response is the ultimate evaluation method to compare commercial products with the same chelating agent or different chelates.     

Effect of phosphorus‐enriched biochar and poultry manure on growth and mineral composition of lettuce (Lactuca sativa L. cv.) grown in alkaline soil

The use of pyrolysis products of manures gives positive effects on soil fertility, crop productivity and soil carbon sequestration. However, effects depend on soil characteristics, plant species and the raw material from which the biochar is derived, and some negative effects of biochar have been reported. The objective of this study was to evaluate the effectiveness of poultry manure (PM)‐derived biochar on the growth, and P, N, K, Ca, Mg, Fe, Zn, Cu and Mn concentration of lettuce (Lactuca sativa L.) plant. The treatments as follows: control, 20 g/kg poultry manure (PM), 20 g/kg phosphorus‐enriched poultry manure (PM+P), 10 g/kg Biochar (B), 10 g/kg Biochar+P (B+P). Application of biochar and PM significantly increased lettuce growth, and P‐enriched forms of PM and biochar gave the higher growth. PM has no significant effect on the N concentrations but biochar and, P‐enriched PM and biochar treatments significantly increased N concentrations. Phosphorus concentration of the lettuce leaves significantly increased by PM and biochar treatments. Plant K concentrations were also increased by PM and biochar, and their P‐enriched forms. Leaf Ca and Mg concentrations were lower in Biochar and B+P treatments than that of PM and PM+P treatments. Compared to control and PM treatments, biochar applications reduced Fe, Zn, Mn and Cu concentrations of the lettuce plants. The results of this study indicated that application of biochar to alkaline soil is beneficial for crop growth and N, P and K nutrition, but it certainly reduced Fe, Cu, Zn and Mn nutrition of lettuce.     

Response of Wheat Plants to Zinc,Iron, and Manganese Applications and Uptake and Concentration of Zinc,Iron, and Manganese in Wheat Grains

This experiment was conducted at Zahak Agricultural Research Station in the Sistan region in southeast Iran. A factorial design with three replications was used to determine the effects of zinc (Zn), iron (Fe), and manganese (Mn) applications on wheat yield, Zn, Fe, and Mn uptakes and concentrations in grains. Four levels of Zn [soil applications of 0, 40, and 80 kg ha^?1 and foliar application of 0.5% zinc sulfate (ZnSO₄) solution], two levels of iron sulfate (FeSO₄; 0 and 1%) as foliar application, and two levels of Mn (0 and 0.5%) also as foliar application were used in this study. Results showed that the interactive effects of Zn and Mn were significant on the number of grains in each spike. The highest number of grains resulted from the application of 80 kg ZnSO₄ ha^?1 and foliar Mn. The interactive effects of Zn and Fe were significant on weight of 1000 grains. The highest weight of 1000 grains resulted from application of 80 kg Zn and foliar Fe. Application of 80 kg ZnSO₄ ha^?1 alone and 80 kg ZnSO₄ ha^?1 with foliar application of Mn significantly increased grain yield in 2003. The 2‐year results showed that foliar application of Zn increased Zn concentration and Fe concentration in grains 99% and 8%, respectively. Foliar application of Fe resulted in a 21% increase in Fe concentration and a 13% increase in Zn concentration in grains. The foliar application of Mn resulted in a 7% increased in Mn concentration in grains.     

Influence of micronutrient and phosphorous levels and chelator to iron ratio on growth,chlorosis, and nutrition of bluecrop highbush blueberries

‘Bluecrop’ blueberry plants were exposed to 2×2×2 factorial treatments of high and low phosphate and micronutrients (Cu, Zn, Mn, and B) and excess or stoichiometric concentrations of a chelator (EDDHA) added to Fe(NO₃), in pH 6.8 solution cultures. The effects on growth, Fe chlorosis and overall nutrition were accessed. Phosphorous was applied at 20 (low) or 400 (high) μM levels, micronutrients at low or high levels and either a 1:1 or 10:1 ratio of chelator to Fe concentration. Plants grown in excess chelator and low micronutrient supply grew normally. Plants grown in all high micronutrient solutions were chlorotic after 34 days. Plants in low micronutrient and stochiometric chelator to Fe ratio solutions were also chlorotic.

Foliar Fe was not a good indicator of Fe chlorosis development. High Cu levels in roots grown in high micronutrients without excess chelator may have been a causative factor in Fe chlorosis development, but not in reducing foliar Fe levels. There was no indication that excess chelator facilitated Fe transport as has been reported for other crops. However, this work demonstrates that highbush blueberry has an effective ability to absorb Fe from strong Fe chelates and remain non‐chlorotic even at high solution pH levels under an all nitrate‐nitrogen regime. Chemical name used: EDDHA‐ethylenediaminedi‐o‐hydroxyphenlyacetic acid.     

Interelemental relationships in the soil and plant tissue and photosynthesis of field‐cultivated wheat growing in naturally enriched copper soils

Several interelemental relationships have been examined in field‐cultivated wheat (Triticum aestivum L. cv Vergina) growing on naturally enriched copper (Cu) soils. Mean soil Cu concentration per site ranged from 103–394 μg.g^‐1 dry weight (DW). Interrelationships between Cu, iron (Fe), calcium (Ca), potassium (K), zinc (Zn), lead (Pb), and magnesium (Mg) concentrations in the soil and plant tissue (roots, stems, and leaves) were examined using Principle Components Analysis. Soil samples were clustered according to collection site and were primarily differentiated according to their Cu concentrations. Soil Cu concentrations were positively correlated with Zn, Ca, Fe, and K in the soil, with Cu, K, and Ca in the roots, and Cu and Fe in the leaves and negatively correlated with Fe in the roots. The increase in Cu in the roots and leaves was positively correlated with increases in K and Ca in the roots and Fe and Ca in the leaves, but negatively with Fe in the roots. Increases in leaf Ca concentrations were correlated with increases in Mg and decreases in Zn concentrations in the leaf. Plants growing in soil with high Cu concentration exhibited toxicity symptoms with reduced height, decreased total leaf area and lower chlorophyll concentrations. Photosynthesis expressed per unit leaf area was not affected by increasing Cu concentrations in the soil or plant tissue.     

The use of iron chelates in compound fertilizers containing trace elements

Abstract

The chemical behaviour of iron chelates, incorporated in compound fertilizers with inorganic micronutrient compounds, was studied. Pot experiments were conducted to evaluate the effectiveness of these products in controlling iron deficiency. A commercial compound fertilizer, containing 0.09% Fe as Fe‐DTPA, 0.12% Cu, 0.16% Mn and 0.04% Zn as sulfates, proved to be ineffective in preventing iron chlorosis in Chamaecyparis lawsoniana ’Alumii’, growing on sphagnum peat at two lime levels. The same fertilizer formulation with 0.09%‐ Fe as Fe‐EDDHA did prevent iron chlorosis at both lime levels. Fe‐EDTA, incorporated in the compound fertilizer, gave good results at the lower but not at the higher lime level, due to the low stability of Fe‐EDTA at high pH. Data from laboratory experiments showed that copper replaced the chelated iron in the compound fertilizer containing Fe‐DTPA, causing the iron to precipitate. The strong competition between copper and iron for the organic ligand is due to a specific affinity of copper for DTPA, resulting in a copper chelate with high stability constant and a molar ratio of copper to chelating agent of 2 : 1.

In the case of Fe‐EDDHA and Fe‐EDTA the competition between iron and copper is much weaker. In contrast to Fe‐DTPA, these chelates remain rather stable when incorporated in fertilizers containing micronutrients.     

Hydroxycinnamic acids as affected by different fertilization of Rebula grapevines

The phenolic composition of white grapes is important since browning reactions may dramatically compromise the overall quality of musts and wines. Only few scientific contributions are available, which investigated how fertilization can influence this class of compounds. Thus, the aim of this work was to examine the effects of NPK soil fertilization coupled with soil or foliar applications of Mg, Fe, and Zn on the concentrations of K, Mg, Fe, and Zn of grape berries and leaf petioles of potted Rebula grapevines (Vitis vinifera L.), also revealing the change of hydroxycinnamic acids in grape juice. The results obtained over the three‐year study (2009–2011) showed that NPK fertilization positively affected K and Zn concentrations of petioles and grape berries, and negatively Mg. In addition, K (synergistic) and Mg (antagonistic) had an influence on Zn uptake. Our findings suggest that the supply of NPK was profitable for a reduction of trans‐caftaric acid in grape juice, while only few differences were observed with further application of nutrients.