Effect of interaction between salinity and nanoparticles (Fe2O3 and ZnO) on physiological parameters of Zea mays L.

A pot experiment was conducted to evaluate the effects of zinc oxide (ZnO) and iron oxide (Fe₂O₃) nanoparticles on the growth of two maize cultivars under the saline condition. Salt stress induced decreases of shoot, root dry weight, leaf area and leaf gas exchange of S.C. 704 more than Bulk. The increase of salinity level, chlorophyll a, b and total chlorophyll content and iron (Fe) and zinc (Zn) concentrations under all spray treatments declined. Application of ZnO and Fe₂O₃ significantly enhanced the root growth (17%), net carbon dioxide (CO₂), assimilation rate (8%) and sub-stomatal CO₂ concentration (5%) of maize compared to control. Nanoparticles of Fe₂O₃ and ZnO caused an increase in leaf Fe (22%) and Zn (11%) concentrations, respectively, compared with normal forms. According to the results, although the alleviation effects of Zn and Fe have been demonstrated under stress conditions, nanoparticles were more effective than normal forms, which may be due to their shape, size, distribution and characteristics.     

Comparison of the effects of nano-iron fertilizer with iron-chelate on growth parameters and some biochemical properties of Catharanthus roseus

Nanofertilizers, which supply nutrients to the plant, are used to replace conventional fertilizers. Iron (Fe) is one of the essential elements for plant growth and plays an important role in the photosynthetic reactions. To study the effects of nano-iron fertilizer on Catharanthus roseus, plants were treated with different concentrations (0, 5 10 20, 30, and 40 mM) of iron oxide nanoparticles (Fe2O3) for 70 days. Fe₂O₃ nanoparticles increased growth parameters, photosynthetic pigments, and total protein contents in the treated plants significantly. The maximum amounts of growth parameters, photosynthetic pigments, and protein contents were obtained with 30 µM Fe₂O₃ and minimum values of these parameters were found with 0 µM Fe₂O₃. The highest value of total alkaloid content was obtained in 0 µM Fe₂O₃ and the lowest value was observed in control plants. Iron oxide nanoparticles increased potassium, phosphorus, and iron absorption but did not show a significant effect on sodium content.     

Use of Composting Manure to Improve Plant Iron and Zinc

Abstract

Laboratory experiments were conducted to determine the influence of three types of decomposing fresh organic materials [pig manure (PM), Astagalus sinicus (AS), and Alternanthera philoxeroides (AP)] on dissolution of Fe₂O₃ and ZnO and also the use of a loamy calcareous soil as an alternative source of iron (Fe) and zinc (Zn). Levels of Fe and Zn concentrations in composting solutions changed with composting time. The maximum levels of solution Fe resulting from the decomposition of the three organic materials were 20, 612, and 348 mg L^?1 for PM, AS, and AP, respectively, when the soil was supplied as the Fe source, and 17, 32, and 16 mg L^?1 when Fe₂O₃ was supplied as the Fe source. Corresponding maximum levels of solution Zn were 0.9, 0.7, and 1.3 mg L^?1 and 35, 171, and 103 mg L^?1 when the soil and ZnO was supplied as the Zn source respectively for the same three organic materials.     

Effects of foliar spray of two kinds of zinc oxide on the growth and ion concentration of sunflower cultivars under salt stress

This study investigated the effects of foliar application of normal and nano-sized zinc oxide on the response of sunflower cultivars to salinity. Treatments included five cultivars (‘Alstar’, ‘Olsion’, ‘Yourflor’, ‘Hysun36’ and ‘Hysun33’), two salinity levels [0 and 100 mM sodium chloride (NaCl)], and three levels of fertilizer application. Fertilizer treatments were the foliar application of normal and nano-sized zinc oxide (ZnO). Foliar application of ZnO in either forms increased leaf area, shoot dry weight, net carbon dioxide (CO₂) assimilation rate (A), sub-stomatal CO₂ concentration (Ci), chlorophyll content, Fv/Fm, and Zn content and decreased Na content in leaves. The extent of increase in chlorophyll content, Fv/Fm and shoot weight was greater as nano-sized ZnO was applied to the normal form. The results show that the nano-sized particles of ZnO compared to normal form has greater effect on biomass production of sunflower plants.     

Mycorrhizal (Rhizophagus Intraradices) Symbiosis and Fe and Zn Availability in Calcareous Soil

Greenhouse experiment was conducted to assess the iron (Fe) and zinc (Zn) fractionation patterns in soils of arbuscular mycorrhizal (AM) fungus-inoculated and uninoculated maize plants fertilized with varying levels of Fe and Zn. Soil samples were collected for Fe and Zn fractions and available Fe, Zn and phosphorus (P) contents besides organic and biomass carbon (BMC), soil enzymes and glomalin. Major portion of Fe and Zn fractionations was found to occur in the residual form. Mycorrhizal symbiosis increased the organically bound forms of Fe and Zn while reducing the crystalline oxide, residual Fe and Zn fractions, indicating the transformation of unavailable forms into available forms. Soil enzymes, viz. dehydrogenase and acid phosphatase activities in M+ soils, were significantly higher than M? soil consistently. Overall, the data suggest that mycorrhizal symbiosis enhanced the availability of Fe and Zn as a result of preferential fractionation and biochemical changes that may alleviate micronutrient deficiencies in calcareous soil.

Abbreviations: AM: arbuscular mycorrhiza; Fe: Iron; Zn: Zinc; P: Phosphorous; Amox-Zn: amorphous oxide bound zinc; Cryox-Zn: crystalline oxide bound zinc; DAS: days after sowing; DTPA: diethylene Triamine Penta Acetic Acid; MnO₂-Zn: manganese oxide bound zinc; OC-Zn: organically bound zinc; WSEX: water soluble plus exchangeable zinc; MnO₂ Fe: manganese oxide bound iron; OC-Fe: Organically bound iron; WSEX Fe: water soluble plus exchangeable iron.     

Effect of iron oxide on phosphate sorption by calcite and calcareous soils

Pure calcite (AR grade CaCO₃) was treated with ferrous perchlorate solution to give a surface coating of iron (Fe) oxide. Maximum sorption (x_m) of phosphate (P) by the calcite increased from 18.2 to 160 mg P kg^?1 as the amount of coating increased from 0.00 to 16.0 g Fe₂O₃, kg^?1 CaCO₃. Evidence for Fe oxide coatings on carbonate minerals in two Sudanese soils was obtained by optical microscopy and electron-probe microanalysis. The relative contributions of carbonate and Fe oxide minerals, and Fe oxide coatings to P sorption in these soils were calculated, based on an assumed model of oxide distribution. Separate-phase Fe oxide was the major contributor (30–40%) to P sorption in the soils; the Fe oxide coatings on carbonate minerals were only minor contributors (< 6%), and the contribution of uncoated carbonate minerals was found to be negligible (<1 %). These results suggest a very minor role for carbonate minerals, even when coated with Fe oxide, in the sorption of P by these calcareous, Sudanese soils.     

Mesoporous SBA-15 Supported Iron Oxide: A Potent Catalyst for Hydrogen Sulfide Removal

A novel silicate mesoporous material, SBA-15 supported Fe₂O₃, was synthesized by post-synthesis method via ultrasonic-assisted route. The desulfurization test from a gas mixture containing 0.1 vol% H₂S was carried out over SBA-15 supported Fe₂O₃ in a fixed-bed system at atmospheric pressure and room temperature. The effects of the chemical nature of Fe₂O₃ and the textural properties of the material on desulfurization capacity were studied. Materials before and after the desulfurization test were characterized using nitrogen adsorption, XRD, TEM, FTIR, XPS, ICP and other standard methods. The characterization results suggest that modification process does not change the two-dimensional hexagonal mesostructure of SBA-15. Iron species disperses inside channels and the outside surface in the crystalline phase of iron oxide. The material with iron content of 31.3 wt% presented highest H₂S uptake capacity. Structural properties of the material also play important roles in desulfurization performance besides the catalytic effects of iron oxide. The basic feature of material and enough oxygen supply are benefit for the reaction. SBA-15 supported Fe₂O₃ can be an effective alternative to capture H₂S from gas streams.     

Porous Materials Modified with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles for Arsenic Removal in Drinking Water

The contamination of drinking water with arsenic has been a problem in a lot of countries around the world because of its toxicological and carcinogenic effects on human health. Porous materials modified with Fe₃O₄ nanoparticles (Fe₃O₄ NPs) represent convenient removers for that contaminant. A co-precipitation method of Fe(III) and Fe(II) in alkaline media was applied to obtain Fe₃O₄ NPs. In a first stage, single nanoparticles were synthesized and stabilized with carboxylic acids. A characterization with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, and X-ray diffraction (XRD) confirms a magnetite-type structure. Moreover, transmission electron microscopy (TEM) and calculations from XRD data using Scherrer’s equation indicate an average particle size of 13 nm and an average crystallite size of 10 nm, both independent of the stabilizer used. Then, the co-precipitation method studied was applied to modify kaolin, bentonite, diatomite, and silica and thus prepare magnetic composites having support-magnetite weight ratios of 2:1. Among them, silica-modified material presented the best hydraulic characteristics, an important aspect for large-scale applications such as removal under gravity. This composite has the capacity to remove up to 80 and 70% for initial concentrations of 25 and 50 μg/L, respectively, representing a convenient remover for processes developed in subsequent stages or in continuous flow.     

Effect of individual and combined exposure of Fe2O3 nanoparticles and oxytetracycline on their bioaccumulation by rice (Oryza sativa L.)

Purpose

It has been reported the bioaccumulation of γ-ferric oxide nanoparticles (Fe₂O₃ NPs) or oxytetracycline (OTC) in crops. However, there have been little references investigating their uptake and bioaccumulation in crops after the combined exposure. The present study focused on Fe₂O₃ NPs and OTC accumulation on root surface and in the tissues of rice (Oryza sativa L.) seedlings under combined exposure. And, the interactive influence mechanism was also discussed.

Materials and methods

Hydroponic experiments were conducted to investigate the Fe and OTC accumulation on root surface and in rice tissues under individual and combined exposure of Fe₂O₃ NPs and OTC. The dynamic change of particulate Fe, ionic Fe, and Fe plaque concentrations on root surface was determined under the influence of OTC from Fe₂O₃ NPs and Fe-EDTA exposure. Fe²⁺ from Fe-EDTA was selected in order to compare the Fe bioaccumulation from ionic Fe and nanoparticle Fe exposure. Hydrodynamic diameter and ζ-potential of Fe₂O₃ NPs in solution were investigated when OTC was present or not, and the changes of OTC concentrations were also determined during hydroponic culture. SEM, XRD, and TEM were used to analyze Fe₂O₃ NP distribution on root surface and inside root under the influence of OTC.

Results and discussion

OTC promoted surface-Fe and shoot-Fe accumulation in Fe₂O₃ NPs treatments, which was just an opposite result from Fe-EDTA treatments. Upon Fe₂O₃ NP exposure, Fe plaque was formed through the direct adsorption of NPs on the outside root surface and then incorporated into plaque as its crystalline components. OTC elevated notably surface-Fe accumulation mainly through increasing adsorption and precipitation of Fe₂O₃ NPs on the root surface due to low repulsive electrostatic interaction between NPs and the root surface after adding OTC. Fe₂O₃ NPs increased surface-OTC and root-OTC levels. Compared to Fe-EDTA, surface-Fe from NP treatments can hold strongly OTC due to Fe₂O₃ particle precipitated on root surface with high specific surface area. NPs reduced shoot-OTC under 25 mg L^?1 OTC, but not under 100 mg L^?1 OTC.

Conclusions

This study clearly demonstrates that Fe/OTC accumulation in rice was always in the order root surface > shoot > root, whether Fe₂O₃ NPs/OTC was individual or combined exposure. The combined exposure will increase their root surface distribution comparing with individual exposure, and Fe₂O₃ NPs increased also root-OTC levels, which could pose a potential risk to food safety in subsequent growth of rice.

     

Characterization of Tolerance Limit in Spirulina platensis in Relation to Nanoparticles

A study was carried out under in vitro conditions to characterize the growth of blue green alga, Spirulina platensis, in standard CFTRI medium containing different nanoparticles of copper oxide (CuO) (50 nm, 10 ppm), zinc oxide (ZnO) (50 nm, 10 ppm), tricalcium phosphate (TCP) (<100 nm, 90 ppm), and hydroxy apatite (HA) (<200 nm, 90 ppm). S. platensis exhibited significant higher growth in standard CFTRI medium containing 90 ppm phosphorus as nanoparticles of TCP and HA. On the other hand, calcium phosphate nanoparticles caused significant reduction in nitrate reductase activity as well as in protein content of the alga. Marked change in chlorophyll-a/b ratio was also noted when phosphorus was supplied through nano tricalcium phosphate and nano hydroxy apatite particles as compared to ionic form (K₂HPO₄). The study revealed that the growth of Spirulina in the presence of ZnO nanoparticles was retarded, while no growth was observed with CuO nanoparticles. It was concluded that alga Spirulina showed much sensitivity to nanoparticles of zinc and copper (<50 nm) and was able to tolerate the toxicity of nanophosphate (tricalcium phosphate <100 nm; hydroxy apatite <200 nm).     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. I. Effect on iron nutrition and iron stress response

Cool white fluorescent (CWF) light reduces Fe³⁺ to Fe²⁺ while low pressure sodium (LPS) light does not. Cotton plants grown under CWF light are green, while those yrown under LPS light develop a chlorosis very similar to the chlorosis that develops when the plants are deficient in iron (Fe). It could be that CWF light (which has ultra violet) makes iron more available for plant use by maintaining more Fe²⁺ in the plant. Two of the factors commonly induced by Fe‐stress in dicotyledonous plants‐‐hydroyen ions and reductants released by the roots‐‐were measured as indicators of the Fe‐deficiency stress response mechanism in M8 cotton.

The plants were grown under LPS and CWF light in nutrient solutions containing either NO₃‐N or NH₄‐N as the source of nitrogen, and also in a fertilized alkaline soil. Leaf chlorophyll concentration varied significantly in plants grown under the two light sources as follows: CWF+Fe > LPS+Fe > CWF‐Fe ≥ LPS‐Fe. The leaf nitrate and root Fe concentrations were significantly greater and leaf Fe was generally lower in plants grown under LPS than CWF light. Hydrogen ions were extruded by Fe‐deficiency stressed roots grown under either LPS or CWF light, but “reductants”; were extruded only by the plants grown under CWF light. In tests demonstrating the ability of light to reduce Fe³⁺ to Fe²⁺ in solutions, enough ultra violet penetrated the chlorotic leaf of LPS yrown plants to reduce some Fe³⁺ in a beaker below, but no reduction was evident through a yreen CWF grown leaf.

The chlorosis that developed in these cotton plants appeared to be induced by a response to the source of liyht and not by the fertilizer added. It seems possible that ultra violet liyht could affect the reduction of Fe³⁺ to Fe²⁺ in leaves and thus control the availability of this iron to biological systems requiring iron in the plant.     

Effects of Foliar Application of FeSO4 and NaCl Salinity on Vegetative Growth,Antioxidant Enzymes Activity,and Malondialdehyde Content of Tanacetum balsamita L.

Salinity is one of the major environmental stressors which has deleterious effects on the growth, development, and yield of crops. Because of the gradual increase in soil and water salinity in the East Azarbaijan, Iran, Tanacetum balsamita L. cultivation in this region has always been associated with many problems. To study the effect of foliar spray of iron sulfate (FeSO₄) (0, 750, and 1500 mg L^?1) under sodium chloride (NaCl) salinity (0, 50, and 100 mM) on some physiological characteristics of Tanacetum balsamita L. plants, an experiment was conducted as a factorial based on complete randomized block design with three replications. Total soluble solids (TSS) and essential oil contents were significantly affected by the interaction effects of FeSO₄ foliar application and salinity levels. The highest TSS and essential oil content were found in the plants under NaCl₀ × FeSO₄ 1500 mg L^?1 treatment combination. Leaf length, leaf fresh and dry weights were influenced by both Fe foliar application and salinity levels. Foliar application of iron (Fe) positively affected leaf length, leaves fresh and dry weights, root fresh and dry weights and peroxidase (POD) content, especially at ₁₅₀₀ mg L^?1. Other traits such as leaf length, leaf fresh and dry weights, malondialdehyde (MDA), POD and catalase (CAT) contents were influenced by salinity levels. For POD, MDA, and CAT contents, the highest values were recorded with NaCl 50 and 100. The highest values of leaf length, leaf fresh and dry weights were found in the control plants.     

Effects of different levels of soil salinity on yield attributes,accumulation of nitrogen,and micronutrients in Brassica spp.

The present study was conducted to assess the effect of soil salinity on yield attributes as well as nutrient accumulation in different plant parts of seven Brassica cultivars from two different species raised in pot culture experiment with two levels of salinity treatments along with control corresponding to soil electrical conductivity (EC) values of 1.65 (S₀), 4.50 (S₁) and 6.76 (S₂) dS m^?1. The experiment was consisted of twelve replications in a completely randomized design. Imposition of salinity stress affected various yield attributing characters including plant height, which ultimately led to severe yield reduction. However, tolerant cultivars, CS 52 and CS 54 performed better under salt treatment showing lesser yield loss. Salinity stress reduced the nitrogen (N) content in leaves of the Brassica plants, which reflected in decreased seed protein content. Reduced accumulation of iron (Fe), manganese (Mn) and zinc (Zn) was observed in leaf, stem and root at flowering and post-flowering stages, while CS 52 and CS 54 showed less reduction than susceptible cultivars under salinity stress.     

Effects of bicarbonate and different Fe sources on vegetative growth and physiological characteristics of bell pepper (Capsicum annuum L.) plants in hydroponic system

In order to determine the best iron (Fe) sources under alkaline conditions, an factorial experiment was conducted based on a completely randomized design with two factors of Fe fertilizer at four forms [iron sulfate (FeSO₄), Fe- ethylenediaminetetraacetic acid (EDTA), Fe- diethylenetriaminepentaacetic acid (DTPA) and Fe- ethylenediamine-N,N’-bis (EDDHA), and sodium bicarbonate (NaHCO₃)] at three levels (0, 10 and 15 mM) with three replications. Results showed that the highest loss of vegetative growth (stem length, leaf number, leaf area, stem diameter, and leaf, stem and root dry weight) and ecophysiological parameters (F_v/F_m, SPAD and RWC) was observed in plants treated with FeSO₄. Alkalinity stress increased proline concentration especially in FeSO₄ treatment. Bicarbonate treatments decreased Fe concentration in plant tissues. Fe-EDTA and Fe-DTPA fertilizer sources acted similar or even better than EDDHA at 10 mM NaHCO₃ concentration, but the best Fe fertilizer source was Fe-EDDHA at 15 mM NaHCO₃ concentration.     

A Stable Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Expanded Perlite Composite Catalyst for Degradation of Rhodamine B in Heterogeneous Photo-Fenton System

A stable and efficient Fe₂O₃/expanded perlite (Fe₂O₃-Ep) composite catalyst was synthesized by a simple hydrothermal method for degradation of refractory contaminants in heterogeneous photo-Fenton system. X-ray diffraction and FT-IR analyses confirmed the presence of the Fe₂O₃ in the synthesized catalyst. The catalytic activity of the Fe₂O₃-Ep catalyst was evaluated by the degradation of rhodamine B (RhB, 5 mg/L) and metronidazole (MET, 5 mg/L) in the presence of H₂O₂ under visible light irradiation. The Fe₂O₃-Ep catalyst exhibited high efficiency for degradation of RhB at a wide pH range from 2 to 10 and showed excellent catalytic property for decomposition of MET as well. The degradation ratio of RhB was achieved 99%, and the removal ratio of COD was 62% within 90 min at the best experimental conditions (0.5 g/L of Fe₂O₃-Ep catalyst, 2 mL/L of H₂O₂). Furthermore, iron leaching of the Fe₂O₃-Ep catalyst during the catalytic degradation reaction was negligible and the catalyst still exhibited high catalytic activity and stability after five cycles. These results show that the catalyst can be used as a highly efficient heterogeneous photo-Fenton catalyst for the degradation of non-biodegradable refractory pollutants in water.     

Effects of foliar spray of nano-particles of FeSO4 on the growth and ion content of sunflower under saline condition

This study investigated the effects of foliar spray of normal and nano-particles of iron sulfate (FeSO₄) on the response of sunflower cultivars to salinity. Treatments included five cultivars (Alstar, Olsion, Yourflor, Hysun36 and Hysun33), two salinity levels (0 and 100 mM sodium chloride (NaCl)), and three levels of fertilizer application. Fertilizer treatments were the foliar application of normal and nano-particles of FeSO₄. Foliar application of FeSO₄ in either form increased leaf area, shoot dry weight, net carbon dioxide (CO₂) assimilation rate (A), sub-stomatal CO₂ concentration (Ci), chlorophyll content, Fv/Fm and iron (Fe) content and decreased sodium (Na) content in leaves. The extent of increase in chlorophyll a content by foliar spray of FeSO₄ nano-particles was significantly greater than normal form. The results showed that the FeSO₄ nano-particles increased biomass production of sunflower plants greater in comparison with normal form, although no significant difference was found between two forms.     

Forms and pedogenic distribution of extractable iron in selected wetland soils in Nigeria

Abstract

The content of various forms of iron (Fe) (free, reducible, and organic) were determined by selective extraction methods in three wetland profiles between 1993 and 1995 seasons. The result showed that Fe distribution was in the order: dithionite (Fe_d) > hydroxylamine (Fe_H) > pyrophosphate (Fe_p) iron in the three pedons. The hydroxylamine‐Fe constituted between 10–42% (1993), 20–47% (1994), and 10–12% (1995) of the total free Fe oxides. The pyrophosphate‐Fe, on the other hand, constituted between 0.2–1.0% (1993), 19–52% (1994), and 3–9% (1995) of the total free Fe oxides. Dithionite‐Fe (total free iron oxides) content increases with the increasing depth, while hydroxylamine‐Fe decreases, suggesting that larger proportions of Fe oxides are present as crystalline forms in the lower horizons. The active Fe ratios were generally high in the top soils and low in the subsoil. It ranged between 0.03 and 0.69 (1993), 0.05 and 68 (1994), 0.05 and 0.53 (1995) in all pedons. This suggests that poor drainage slowed down soil development. Highly significant correlations (0.1%) were evident between phosphorus (P) and organic carbon; ECEC and base saturation; Fe_H and active Fe ratio. Significant correlations (1%) were also evident between Fe²⁺ and organic carbon; P and Fe_H; ECEC and clay. Furthermore, significant correlations (5%) were also obtained between clay and Fe_d; pH and Fe_d; active Fe ratio and P; Fe_H and clay; active Fe ratio and Fe_d.     

Removal of As(III) from Aqueous Solution Using Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles: Process Modeling and Optimization Using Statistical Design

In this study, Extran (biodegradable surfactant) was used for the preparation of Fe₃O₄ nanoparticles by microemulsion process to improve removal efficiency of As(III) from aqueous solution. Fe₃O₄ nanoparticles were characterized by XRD, FTIR, FESEM, TEM, HRTEM, and VSM instrumental techniques. The effect of different parameters such as adsorbent dose, initial As(III) concentration, and solution pH were studied by response surface methodology (RSM) based on Box-Behnken design (BBD). The optimized condition for adsorption of As(III) from aqueous solution was obtained as adsorbent dose of 0.70 mg/g, solution pH of 7.7, and initial As(III) concentration of 33.32 mg/L. In this optimum condition, about 90.5% of As(III) was removed from the aqueous solution. Isotherm studies have been done at optimal condition, and it was observed that the Langmuir isotherm models were fitted well with experimental data having a high correlation coefficient of 0.993. From the Langmuir isotherm data, the maximum adsorption capacity of Fe₃O₄ nanoparticles was found to be 7.18 mg/g at pH 7.7 in room temperature. This study revealed that Fe₃O₄ nanoparticles can be used as an efficient, eco-friendly, and effective material for the adsorptive removal of As(III) from aqueous system.     

Changes of redox and pH conditions in a flooded soil amended with glucose and manganese oxide or iron oxide under laboratory conditions

The changes of Eh and pH in soil suspension (Ah-horizon of a Mollic Gleysol) and Mn²⁺ or Fe²⁺ concentrations in the equilibrium soil solution at different levels of glucose (0%, 0.5% and 1%) and MnO₂ (0%, 0.025%, 0.05% and 0.1%) or Fe₂O₃ (0%, 0.025%, 0.05% and 0.1%) were examined. It was found that the degree of Mn- and Fe-reduction in soil depends mainly on the presence and the amount of an easily decomposable carbon source and to a minor degree on the content of native or added forms of MnO_O2 or Fe₂O₃ in the soil. Theoretical relationships between the water soluble manganese and iron and the Eh and pH values have been verified, when the observed initial drop of Eh was eliminated. It was found that the water soluble manganese content was described best by the Mn₂O₃/Mn²⁺ redox system, and that of iron by the Fe₃ (OH)₃/Fe²⁺ system.     

Phosphorus adsorption by a range of western Australian soils related to soil properties

Abstract

The capacity of 36 Western Australian soils to adsorb phosphorus (P) was measured by three different methods: P retention index (PRI), P buffering capacity (PBC), and P adsorption (PA). The P adsorption values measured by all three methods varied markedly with soil type. When the P adsorption values were correlated with several soil properties, using simple and multiple linear regressions, PRI, PBC, or PA values were found to be significantly correlated with the aluminium oxide content of the soils. In addition, PBC and PRI was correlated with organic carbon content. The role of aluminium oxide (Al₂O₃) in the soil was apparently more important in determining the P adsorption capacity of the soils than that of iron (Fe), even though the iron oxide (Fe₂O₃)content of all the soils studied was consistently higher than the aluminium oxide content. The relationship between P adsorption and the selected soil properties, as determined by multiple linear regression, explained 45–59% of the variation: arabic PRI = ‐10.87 + 9.94 organic C (%) + 160.02 Al₂O₃ (%), r² = 0.45.

arabic PBC = ‐0.004 + 1.532 organic C (%) + 22.26 Al₂O₃ (%), r² = 0.57.

arabic PA = 3.52 + 248.75 Al₂O₃ (%), r² = 0.59.