Iron-chelates evaluation in a calcareous soil

A greenhouse pot experiment withLolium multiflorum, cv. Tetila, grown in a calcareous soil was carried out to determine the efficiency of iron-chelate (Fe-EDTA,-DTPA,-EDDHA and Rexene) as soil amendments. In the soil solution Fe was displaced more readily from EDTA chelate and less so from EDDHA chelate. A significant increase of Mn, Cu and Zn in the soil solution was observed, with Fe-DTPA; Cu and Zn with Fe-EDTA; Cu with Rexene and, with Fe-EDDHA after 14 days. Plant took up more Fe from Rexene treatment than from the other treatments, Fe-EDDHA was the least efficient. In general, Mn, Cu and Zn concentrations in the leaf diminish in all the treatments compared with the control.     

Lolium multiflorum uptake of iron supplied as different synthetic chelates

The plant availability of Fe from synthetic chelates has not been examined extensively for plants having the second strategy in iron uptake. Since these plants also excrete chelating agents, competition between natural and synthetic ligands is expected. This research was conducted to study the efficiency of different iron-chelates (Fe-EDTA, Fe-DTPA, Fe-EDDHA and a commercial product, Rexene) inLolium multiflorum iron nutrition. Plants were grown in a greenhouse with hydroponic culture using a buffered nutrient solution at pH 8. Initial iron concentration in the nutrient solution was near 0.5 mgl^–1 and solutions were replaced weekly. In an other Fe-EDTA treatment the same amount of chelate was supplied by four additions during each week.Changes of iron concentration in the nutrient solution, harvestable yield, Fe, Mn, Cu and Zn content in plant tissue and chlorophylllevels in leaves are discussed as parameters to evaluate chelate efficacy. Fe-EDDHA, without inorganic iron in the medium was not as effective as the commercial product Rexene, containing Fe-EDDHA and some extra weakly complex iron, which gave the highest yields. Fe-EDTA applied once a week with fresh nutrient solution was less effective than a four part addition as seen from Chl₁/[Fe] ratios.     

Behaviour of iron chelates in calcareous soils

Summary An examination was made of the changes with time in the composition of aqueous extracts of a highly calcareous clay that had been treated with one of the four chelates Fe-DTPA, Fe-CDTA, Fe-HEEDDA and Fe-EDHPA (Fe-Chel 138).It was found that a rapid fall in the recovery of soluble iron took place with both Fe-DTPA and Fe-HEEDDA due to sorption by the clay and also to replacement of iron in the chelate by calcium from the soil. By using Fe⁵⁹-labelled compounds, it was found that for both these chelates considerable isotopic exchange occurred between the Fe⁵⁹ and the natural soil iron, and that this exchange increased with decreasing rate of application of chelated iron.Fe-CDTA and Fe EDHPA were found to be comparatively unaffected by contact with the soil; over 80% recovery was obtained after 15 days, with treatments ranging from 2.5 to 100 ppm chelated iron. Negligible isotopic exchange took place with these two chelates.These results are discussed in relation to previously published results of laboratory experiments with iron chelates and to the treatment of soils for the control of iron chlorosis.     

Studies on the manganese uptake of lettuce on steam-sterilised glasshouse soils

Summary During steam sterilisation of glasshouse soils appreciable amounts of easily reducible manganese are converted into exchangeable manganese. The reverse process takes place much more gradually. As a result, manganese toxicity occurs in several crops on newly steamed soils. In the Netherlands, lettuce has been found to be particularly prone to manganese toxicity. An investigation was carried out to obtain more information about the manganese status of steamed glasshouse soils in which lettuce was used as the test crop. The following results were noted.The uptake of exchangeable manganese is easier in the lighter soils than in heavy soils. Application of iron to the soil inhibits manganese uptake by the plant, but the iron must be applied in the form of chelate. The pH has a profound effect on manganese uptake on steamed as well as on unsteamed soils. However, the relationship between the pH and the manganese content of the crop on steamed soils is different from that found on unsteamed soils.The slow rate of oxidation of manganese in steamed glasshouse soil may be explained by the fact that the oxidising bacteria are killed during the steam sterilisation process. The fixation of manganese can be accelerated appreciably by inoculating the steamed soil with manganese-oxidising bacteria.The effect on manganese uptake of five soil desinfection chemicals used in the investigation proved to be very small.The lettuce varieties used in the Netherlands show a wide variation in susceptibility to manganese toxicity. This cannot be explained by different rates of manganese uptake. It is more likely that the varietal differences are based on different levels of resistance to manganese present in the plants.     

Mobilisation of iron and manganese by plant-borne and synthetic metal chelators

Phytosiderophores released by roots of iron-deficient grasses mobilise Fe, Zn, Mn and Cu in calcareous soils. Mobilisation of Fe, Zn and Cu can be explained as the chelation of these metal cations by phytosiderophores. Mobilisation of Mn could not be so explained because phytosiderophores have a much smaller affinity for Mn than for Fe, Cu and Zn. Model experiments have been made with freshly precipitated Fe(OH)₃ and different soils to study the mobilisation of iron and manganese by plant-borne chelating phytosiderophores, the synthetic metal chelators DTPA and the microbial metal chelator sulphonated ferrioxamine B (FOB). Compared with the synthetic chelator DTPA, the plant-borne chelating phytosiderophores mobilised Fe very efficiently, but no change was observed in the Mn mobilisation by phytosiderophores.Different phytosiderophores, as well as the microbial metal chelator FOB, were used to compare the mobilisation of iron and manganese in a calcareous soil.     

Evaluation of different iron compounds in chlorotic Italian lemon trees (Citrus lemon).

The severe deficiency of iron or ferric chlorosis is a serious problem of most citrus trees established in calcareous soils, as a result of the low availability of iron in these soils and the poor uptake and limited transport of this nutrient in trees. The objective of this study was to evaluate the response of chlorotic Italian lemon trees (Citrus lemon) to the application of iron compounds to roots and stems. On comparing the effects of aqueous solutions of ferric citrate, ferrous sulphate and FeEDDHA chelate, applied to 20% of the roots grown in soil and sand, of trees that were planted in pots containing calcareous soil, it was observed that the chelate fully corrected ferric chlorosis, while citrate and sulphate did not solve the problem. EDDHA induced the root uptake of iron as well as the movement of the nutrient up to the leaves. With the use of injections of ferric solutions into the secondary stem of adult trees, ferric citrate corrected chlorosis but ferrous sulphate did not. The citrate ion expanded the mobility of iron within the plant, from the injection points up to the leaves, whereas the sulphate ion did not sufficiently improve the movement of iron towards the leaf mesophyll.     

Reactions of iron chelates in calcareous soil and their relative efficiency in iron nutrition of corn

Summary Laboratory incubation studies on the reactions of Fe-DTPA, Fe-EDTA, Fe-citrate and Fe-fulvate with a calcareous soil indicated that Fe³⁺ was very rapidly displaced by Ca²⁺, Mg²⁺, Zn²⁺ and Cu²⁺ ions. The displacement of iron was in the reverse order of the stability of the Fe-chelates. The activity of Fe³⁺, Ca²⁺, Mg²⁺, Zn²⁺ and Cu²⁺ tended to attain a constant value with time. Application of chelating agents to a calcareous soil mobilized different amounts of iron as defined by their relative stability and cation competition. The degree of mobilization increased with increasing levels of applied chelating agents. A significant negative correlation (r = –0.77)^* was observed between pH and DTPA-extractable iron. Results of greenhouse experiment showed significant increase in the dry matter yield and iron uptake by corn plants upon application of iron-chelates. The chelates enhance the uptake of both native and applied sources. The effectiveness of the chelates used was in the order of their capacity to maintain iron in soluble form in the soil solution. These results suggest that iron nutrition of plants in calcareous soils can be effectively regulated by the application of iron chelated by natural or synthetic water-soluble chelating agents.     

短链聚磷酸磷肥对土壤无机磷转化及铁锰锌有效性的影响

明确聚磷酸形态磷在土壤中的转化及其对土壤磷有效性的影响是聚磷酸类磷肥合理施用的前提.本研究通过盆栽试验比较了施用磷酸一铵和聚磷酸类磷肥对石灰性土壤和酸性红壤有效磷、无机磷转化和土壤微量元素活化的影响,同时研究了不同磷源在油菜上的施用效果.结果表明: 聚磷酸磷肥可显著提高石灰性土壤磷的有效性.与磷酸一铵(MAP)处理相比,聚磷酸处理的土壤水溶性磷和有效磷平均含量分别提高了19.0%和25.4%;对土壤无机磷连续浸提试验表明,Resin-P(树脂磷)和NaHCO₃-P(高活性磷)较MAP处理分别提高了22.8%和43.3%,NaOH-P(中活性磷)较MAP处理提高了33.8%,说明聚磷酸磷肥可显著减少石灰性土壤对磷的固定.在酸性红壤上,施用聚磷酸类磷肥对提高土壤磷的有效性及减少磷的固定效果不明显.聚磷酸磷肥可显著提高石灰性和酸性土壤Fe、Mn、Zn的有效性.与MAP处理相比,聚磷酸肥料处理下石灰性土壤有效Fe、Mn、Zn分别提高了2.1%、16.2%和20.8%,红壤的有效Fe、Mn、Zn含量分别高了6.6%、11.9%和9.2%.聚磷酸磷肥显著提高了石灰性土壤上油菜干物质、吸磷量和磷肥利用率,但在酸性红壤上聚磷酸磷肥处理肥料效应却低于MAP处理.总之,聚磷酸磷肥在提高石灰性土壤中磷的有效性、减少磷的固定、活化Fe、Mn、Zn等微量元素以及改善油菜磷素营养方面均具有显著效果,是在石灰性土壤上能有效替代正磷酸磷肥的新型磷肥.     

Functional Analysis of the Genotypic Differences in Response of Pea (<i>Pisum sativum</i> L.) to Calcareous-Induced Iron Deficiency

Lime-induced iron chlorosis is a major nutritional disorder causing severe plant growth and yield reduction in the calcareous soils of Tunisia. The understanding the behavior of key metabolic functions of peas on calcareous soils, the identification of useful traits of tolerance, and the exploration of the genotypic differences in response to this constraint remain the most efficient approaches due to their coast, environmental benefits, and sustainability. For this purpose, a greenhouse experiment was conducted on three pea genotypes (Alexandra: Alex, Douce de provence: DP, and Merveille de Kelvedon: MK) cultivated on calcareous soil (Fe-deficient) and fertile soil (control). Plant growth, SPAD index, iron nutrition and distribution, photosynthesis, and antioxidant enzymes were deeply analyzed to discriminate genotypic differences. Calcareous-induced iron deficiency reduced SPAD index, plant growth, net photosynthesis, and tissue Fe content against a significant stimulation of the oxidative stress indicators, H₂O₂ and Malondialdehyde (MDA). Moreover, we reported a significant induction of SOD and CAT activity in shoots and roots of the Alexandra genotype. Fe use efficiency increased on calcareous soil and clearly discriminated the studied genotypes. Alexandra genotype was found to be the most tolerant to lime-induced iron chlorosis. This genotype protects its tissues against oxidative stress by stimulating enzyme activities (SOD and CAT) and develops significant efficiency of Fe uptake, translocation to shoots and use when cultivated on calcareous soil.     

Grain sorghum (Sorghum bicolor Pers.) responses to organic iron on calcareous soils

Effects of Fe-EDDHA (Sequestrene 138), Fe-polyflavonoid (Rayplex), and an experimental iron lignosulfonate on dry matter yields, Fe content, and plant chlorosis of grain sorghum were studied under controlled conditions, using a normal and an Fe-deficient soil (DTPA extract). Application rates of 20, 40, and 80 ppm Fe were employed. Dry matter yields increased due to Fe applications. The lignosulfonate (Fe-LS) produced maximum dry matter yields followed by Fe-EDDHA and the polyflavonoid (Fe-PF) material. At the 80 ppm rate Fe-EDDHA and Fe-PF produced moderate and slight toxic effects, respectively. No toxic effect was noted with the Fe-LS material. Fe-EDDHA was found to be the most effective for correcting iron chlorosis, while the other two sources were similar in this respect. Except for the Fe-LS applied to the normal soil, all other treatments increased Fe content of plant shoots. In the Fe-deficient soil, Fe application lowered the Ca, Mg, Zn, and Mn concentrations in the plants. In the case of the normal soil, concentrations of these elements increased at the 20 ppm rate and underwent no further changes with higher rates. Treatments did not influence K and P concentrations of plants.Additional index words: Micronutrients, Iron compounds.     

Trace element budget in an African savannah ecosystem

The concentration of selected trace elements (Co, Cu, Fe, Mn, Mo, Se, and Zn) were analysed in soils, grass, bush, and tree samples from the Mole National Park, Ghana. The distribution of the essential nutrients: cobalt, copper, manganese, and selenium is controlled by bedrock geology, whereas iron, molybdenum, and zinc distribution is controlled by soil and hydrological processes. In the soils, iron, manganese, and cobalt are largely fixed in the mineral fraction while most of the copper, molybdenum, and selenium in the soils can be extracted by disodium ethylenediaminetetracetate. Copper, cobalt, and manganese appear to be preferentially concentrated in grass species while molybdenum and selenium are concentrated in browse plants. Variations in uptake exist between wet and dry seasons with all trace elements studied, except iron and manganese, showing a marked increased availability in the wet season and increased concentration in the residual fraction of the mineral and organic soils in the dry season. In the dry season the plant concentration of molybdenum and selenium decreased while copper and zine showed increased concentrations and this may be related to a lower pH of the groundwaters at this time. A budget of metal input and output in the ecosystem at Mole has been computed. From this potential dietary deficiencies in cobalt can be observed, however for other metals soil and plant concentrations are sufficient to prevent straightforward deficiencies while the concentrations of molybdenum and selenium are sufficiently low to be considered safe.     

Uptake of six heavy metals by oat as influenced by soil type and additions of cadmium,lead, zinc and copper

Summary The influence of heavy metal additions on availability and uptake of cadmium, lead, zinc, copper, manganese and iron by oat was studied. The experiments were carried out as pot experiments using sandy loam, sandy soil and organic soil. Selective extractants were used to remove metals held in different soil fractions.Lead and copper were preferently bound by organics and oxides, zinc by oxides and inorganics, and cadmium by inorganics and organics.Addition of cadmium to the soils resulted in higher cadmium concentrations in all plant parts but lower concentrations of lead, zinc, copper, manganese and iron, and the accumulation indexes of these metals were also lower when cadmium was added to the soil.Addition of cadmium plus lead, zinc and copper resulted in higher cadmium concentrations in leaves and straw of plants grown in sandy loam and sandy soil, but lower concentrations when plants were grown in organic soil as compared with the results when cadmium was added separately. The transfer of cadmium, lead, zinc and copper from soil to plant was greatest from sandy soil, and zinc and cadmium were more mobile in the plant than were lead and copper.Cadmium concentrations in leaves correlated significantly with CaCl₂ and CH₃COOH extractions in sandy loam and sandy soil and with CH₃COOH extractions in organic soil.Generally, the total metal uptake was lowest from organic soil.     

Influence of soil waterlogging on subsequent plant growth and trace metal content

Summary The uptake of trace metals by two plant species (French bean and maize) has been measured on two soils subjected to various waterlogging regimes. Uptake of both manganese and iron was increased due to soil waterlogging, although reoxidation of the soil affected iron more than manganese. Zinc and copper uptake was influenced by a species factor; French bean (Phaseolus vulgaris) showed preferential uptake of zinc, whereas maize (Zea mays) took up copper preferentially. Uptake of cobalt by both species was increased due to waterlogging, following the pattern of manganese.The abilities of these species to take up trace metals from soil followed the pattern predicted by selective extraction of soil for manganese, iron and cobalt, but not for zinc and copper.     

Organic solid wastes from urban environment as iron sources for sorghum

Sorghum (Sorghum bicolor L. Moench) which is susceptible to Fe deficiency was grown in two different soils in a glasshouse with two different organic urban wastes (sewage sludge and dog manure) to ascertain their ability to supply Fe and other micronutrients to plants. One soil was calcareous with a history of Fe deficiency. Sewage sludge and dog manure at an application rate of 15,000 g/g to this soil effectively supplied Fe to plants. This effect was not present when the ash rather than the organic matter was used. Ferrous sulfate and Fe-EDDHA (Fe[ethylenediamine di-0-hydroxyphenylacetate]) likewise were not effective. Infrared spectra revealed differences in the fulvic acid for the two sources of solid wastes. The results imply that some sources of organic wastes may be useful in prevention or correction of Fe deficiency in calcareous soils.     

Copper concentration in plants and in the rhizosphere as influenced by the iron status of tomato (Lycopersicon esculentum L.)

Changes of metal concentration that occur in the rhizosphere may arise from several processes including variation in the concentration of complexing ligands, pH or redox potential that can be influenced by the Fe status of the plant. The aim of this study was to assess for both acidic and calcareous, Cu-contaminated soils how Cu concentration in plants and in the rhizosphere was affected by the Fe status of a strategy I plant species. The change of soil solution pH, total solution Cu concentration and soil redox potential was monitored for 8 days in the rhizosphere of tomato (Lycopersicon esculentum L.) in response to contrasting Fe supply. The concentration of Cu in roots was enhanced under Fe deficiency in the acidic soils. Shoot Cu however did not vary with the Fe status of the plant. The plant Fe status had little effect on rhizosphere pH, redox potential or Cu concentration in solution in either acidic or calcareous soils. Marked differences in pH and solution Cu concentration were observed between rhizosphere and uncropped soils. Roots induced an increase in pH of acidic soils and a decrease in solution Cu concentration in all soils. The decrease in solution Cu concentration in acidic soils may be explained by the increase in rhizosphere pH. The proposed device provided new data on the fate of Cu in the rhizosphere and showed a positive correlation for the four soils considered together between the total Cu concentration in soil solution and root Cu concentration.     

Metal complexes of lactoferrin and their effect on the intracellular multiplication of Legionella pneumophila

The action of bovine lactoferrin saturated with iron, zinc and manganese on the intracellular multiplication of Legionella pneumophila in HeLa cells has been tested. The results obtained showed that lactoferrin did not influence the invasive efficiency of Legionella. The intracellular multiplication of the bacterium was inhibited by apo-lactoferrin and by lactoferrin saturated with manganese and zinc, whereas lactoferrin saturated with iron enhanced the intracellular growth. Experiments in parallel were performed with iron, manganese and zinc citrate to test the effect due to the metal ions alone. Even in this condition the addition of an iron chelate enhanced the multiplication of Legionella while the manganese chelate produced a certain inhibition.     

The interrelationship between plant species distribution and properties of soils undergoing podzolization in a coastal area of S.W. Australia

A study of soil and vegetation characteristics within a small area of coastal heath near The Gap, Albany, Western Australia, showed that significant differences exist in plant species composition between podzol and non-podzol (calcareous) soil environments. Leaf extracts of common plant species from podzol, non-podzol and transitional soil sites were tested for their ability to complex with iron. Only those species on the podzol and transitional soils proved to have this ability. Soil column experiments tested the rates of iron mobilization and results indicate that the podzol vegetation elutant solution, which was found to contain the iron-complexing agent gallic acid, was superior to the non-podzol vegetation elutant solution in the rate at which it mobilized iron. It is suggested that initiation of podzolization is due to the presence of gallic acid in the leaves of certain of the species in the coastal heath association, and that the pattern of podzol distribution can be linked to both plant succession and inherent differences in soil parent material.     

Evaluation of early generations for iron chlorosis in relation to productivity in groundnut (Arachis hypogaea L.)

Five popular but iron-inefficient cultivars were crossed with three efficient genotypes and both parents and F₁s were evaluated for iron-efficiency in potted calcareous and noncalcareous soil. The iron-efficient genotypes were dark green or green in both noncalcareous and calcareous soils whereas inefficient types were light green to yellow in calcareous soil. The chlorophyll and active iron (Fe²⁺) concentration of leaves was less in iron-efficient genotypes compared to efficient types in calcareous soil and reduction of both the parameters from noncalcareous to calcareous soil was considerably high in iron-inefficient lines. There was significant correlation between visual scores, chlorophyll and active iron content. There were no differences among F₁s for iron chlorosis and they were all iron-inefficient. The frequency of iron-inefficient plants was higher than the efficient plants in all F₂ populations. But most of the productive plants came from iron-efficient segregants indicating strong association between iron-efficiency and productivity. Based on the results selection for iron-efficiency in early generations and extensive evaluation for productivity in advanced generations is suggested for developing varieties for cultivation in calcareous soils.     

Some ecophysiological and historical approaches to species richness and calcicole/calcifuge behaviour — contribution to a debate

Species richness in vascular plants was related to the plants’ calcifuge or calcicole behaviour using documentation from forests and open-land vegetation at about one thousand sites in the southern parts of Sweden. It is concluded that vegetation of strongly acid soils (pH-KCl < 4.5) have fewer vascular plant species than comparable vegetation of other soils, whereas there are no consistent differences in species richness between slightly-moderately acid and calcareous sites. Low species richness is particularly related to high concentrations of Al³⁺ and H⁺ ions (either soil solution concentrations or concentrations of exchangeable ions), not to a lack of calcium carbonate. The majority of plant species are able to render the sparingly soluble phosphate, iron and manganese compounds of high-pH soils available, but they are unable to tolerate much Al³⁺ or H⁺. Acidicole (calcifuge) species have developed the power of tolerating Al³⁺ and H⁺, which may be considered a secondary property of plants, but they have lost the power of solubilizing critical mineral nutrients in high-pH soils. The reasons why these ecophysiological properties are inversely related in the current flora are obscure, difficult to account for experimentally and a main ecological problem. In areas with cool-temperate climates the flora was partly or mainly extinguished by the Pleistocene glaciations. Comparatively fewer calcifuge than calcicole species have, since then, had enough time to develop, and the number of calcifuges is lower, in spite of the fact that most natural and seminatural soils of these areas are nowadays acidic.