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  • 1
    Electronic Resource
    Electronic Resource
    Thermoplastic matrix controlled-release zinc fertilizers (1988)
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 235-250 
    Details
    ISSN: 1573-0867
    Keywords: Zinc fertilizer ; controlled-release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Thermoplastic matrix controlled-release (C.R.) zinc fertilizers are produced by extruding a mixture of zinc salt and inert polymer material. Three methods of laboratory evaluation were used to characterize a range of C.R. zinc formulations differing in concentration and nature of zinc salt, carrier matrix, and size. The methods were (i) electron microscopy, (ii) zinc emission into water, and (iii) zinc diffusion in indicator-agar. These methods complemented each other, with electron microscopy elucidating physical features governing zinc release from the fertilizer pellets. Finely divided particles of soluble zinc salt, for instance, were associated with formulations whose release characteristics approached theoretical (time)0.5 -order release kinetics. Apart from zinc particle size, other factors controlling zinc emission characteristics were the type of zinc salt, the zinc loading, and pellet size. Varying the polymer matrix materials had little or no effect on zinc release from the C.R. zinc formulations compared in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049580
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  • 2
    Electronic Resource
    Electronic Resource
    Thermoplastic matrix controlled-release zinc fertilizers (1988)
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 251-266 
    Details
    ISSN: 1573-0867
    Keywords: Zinc ; controlled-release ; diffusion ; pH ; temperature ; phosphate ; clay ; sand ; moisture content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The emission and movement of zinc from planar arrangements of controlled-release (C.R.) thermoplastic matrix zinc fertilizer formulations was studied in cylindrical diffusion cells packed with a clay or a sand. The influences of a number of soil characteristics known to affect zinc diffusion were also investigated. Zinc emission was initially (over 2 days) very rapid. The rate declined markedly thereafter. Morphologically distinct C.R. zinc formulations released zinc at different rates. Zinc moved appreciably and consistently further in the sand than in the clay. Of the soil characteristics studied, increasing phosphate levels had no effect upon zinc emission or mobility in either soil. Increasing pH in the sand did not affect zinc emission, but decreased zinc mobility. Conversely, in the two soils, increasing temperature stimulated zinc emission, but had little influence on zinc mobility. At higher water contents, zinc release was increased in both soils. However, zinc movement was only increased in the sand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049581
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  • 3
    Electronic Resource
    Electronic Resource
    Thermoplastic matrix controlled-release zinc fertilizers (1988)
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 267-283 
    Details
    ISSN: 1573-0867
    Keywords: Zinc ; controlled-release ; linseed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Thermoplastic matrix controlled-release (C.R.) zinc fertilizers were compared as zinc sources for linseed (Linum usitatissimum) grown on a zinc-deficient sand and a zinc-deficient clay. C.R. formulations differed in characteristics including origin (different extruders), type of zinc salt, and polymer matrix blends. Conventional fertilization with pure zinc salts was also included in the comparison. C.R. formulations based on zinc oxide (ZnO) were ineffective zinc sources, linseed growth and tissue zinc concentrations being similar to untreated controls. However, both zinc sulphate (ZnSO4·H2O)- and zinc chloride (ZnCl2)-based formulations were effective zinc fertilizers. A group of ZnSO4·H2O-based formulations produced in Melbourne (Australia) gave relatively higher plant zinc concentrations than similar formulations produced on a different extruder in Akron (U.S.A.). Varying the type of plastic or the blend of plastics constituting the matrices of the C.R. products had no consistent effects on tissue zinc concentrations or plant growth. Similarly, no specific benefit of C.R. over conventional zinc fertilization was established under the conditions of the present experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049582
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  • 4
    Electronic Resource
    Electronic Resource
    Factors affecting aluminium sorption by calcium pectate (1993)
    Springer
    Plant and soil 149 (1993), S. 87-94 
    Details
    ISSN: 1573-5036
    Keywords: aluminium ; calcium ; calcium pectate ; polygalacturonic acid ; solution pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Extracellular processes, particularly the adsorption of aluminium (Al) by pectate in the cell wall, have been proposed as important in the expression of Al toxicity to plant roots. In vitro studies were conducted on the effects of Al concentration (generally ≤ 32 μM), calcium (Ca) concentration (0.05 to 10 mM) and pH (3.2 to 5.4) on Al sorption by Ca pectate. There was a rapid reaction between Al and Ca pectate, there being no difference in Al remaining in solution after reaction times of 1 to 16 min, and only a slight decrease after 24 h. Increased Al concentration in solution increased linearly the sorption of Al by Ca pectate, with 70 to 84% of the Al originally in solution sorbed with ≤32 μM Al. In contrast, Al sorption decreased with increased Ca concentration in solution, and as pH decreased from 5.4 to 3.2. Only ≤30% of the sorbed Al was desorbed after 1 h by 1 mM CaCl2, 10 mM CaCl2 or 1 mM HCl. The amount of Al desorbed increased with a desorption period of 5 h, particularly with 1 mM HCl. These studies suggest that Al sorbed by Ca pectate in root cell walls is in equilibrium with Al in solution, and that Al toxicity is associated with the strong binding between Al and Ca pectate external to the cytoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010765
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  • 5
    Electronic Resource
    Electronic Resource
    Use of GEOCHEM-PC to predict rare earth element (REE) species in nutrient solutions (1993)
    Springer
    Plant and soil 155-156 (1993), S. 251-254 
    Details
    ISSN: 1573-5036
    Keywords: cerium ; computer simulation ; lanthanum ; nutrient solutions ; phosphate precipitation ; REE species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The interpretation of results of some experiments examining effects of rare earth elements (REE) on plant growth may have been complicated by rare earth phosphate precipitation. Simulations were undertaken using the computer model GEOCHEM-PC to define REE solubility limits and predict REE species in low and high ionic strength nutrient solutions. In low ionic strength solutions containing 5 μM P, lanthanum phosphate (LaPO4) precipitation is predicted to occur at solution pH〉4.0, reaching a maximum (〉95% of total) at pH 5.5. In high ionic strength solutions (1000 μM P) over 95% of the La is predicted to precipitate as phosphate at pH〉4.0. The predicted behaviour of cerium (Ce) was closely similar to that for La. At pH 5.5, the concentration of REE species in solution can be increased only after virtually all the P has been precipitated. Consequently, it is important to consider REE-P interactions in nutrient solutions when investigating REE effects on plant growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025031
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  • 6
    Electronic Resource
    Electronic Resource
    Mineral nutrient disorders of root crops of the Pacific: Preliminary observations on sweet potato (Ipomoea batatas) (1993)
    Springer
    Plant and soil 155-156 (1993), S. 263-267 
    Details
    ISSN: 1573-5036
    Keywords: critical concentration ; magnesium ; manganese ; nitrogen ; phosphorus ; potassium ; solution culture ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Solution culture was used to characterise deficiencies or toxicities of several essential elements in Ipomoea batatas cv. Wanmun, and to define the critical concentrations of these elements in young mature leaves during vegetative growth. Tentative critical concentrations for deficiency, expressed on the basis of dry weight of leaf blade, were: nitrogen 3.8%, phosphorus 0.17%, potassium 2.4%, magnesium 0.12%, manganese 20μg/g and zinc 10μg/g. For manganese and zinc toxicities it was possible only to designate the range within which the critical concentration occurred. Visible symptoms are briefly described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025033
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  • 7
    Electronic Resource
    Electronic Resource
    Chromatographic techniques for the separation of Al and associated organic ligands present in soil solution (1995)
    Springer
    Plant and soil 171 (1995), S. 29-34 
    Details
    ISSN: 1573-5036
    Keywords: aluminium ; chromatography ; dissolved organic carbon ; organic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Organic acids including humic, fulvic, aliphatic and aromatic acids comprise part of the dissolved organic carbon (DOC) present in soil solution. They act as ligands for trace metals and are effective detoxifiers of monomeric aluminium (Al). Solid phase extraction (SPE) techniques permit fractionation of the DOC into organic classes but yield no information on the pre-existing Al/organic acid complexes. Aliphatic and aromatic acids may be separated and determined by High Performance Liquid Chromatography (HPLC); however, the conditions used dissociate the organic acid Al complexes. Humic and fulvic acids are of a variable and ill-defined nature and only limited information exists regarding their binding of Al. This paper reports on fractionation studies of soil solutions, using both SPE and molecular weight cut-off filters, to characterise the DOC components and on the subsequent development of a size exclusion chromatography (SEC) system for the separation of organically complexed Al into different species using a low ionic strength mobile phase at pH 4.2. Model complexes of Al and Cu citrate were used to evaluate chromatographic performance of a Fractogel TSK HW-40(S) column (1×30 cm). For soil solution samples, the column eluate, after passing through a UV detector, was directly coupled to an Inductively Coupled Plasma Atomic Emission Spectrometer (ICPAES) for on-line multi-element detection to characterise DOC and trace metal distribution. Fractionation studies revealed that polysaccharides constituted the major proportion of the DOC which passed the 10000 dalton molecular weight cut-off filter. Analysis of soil solutions from an organically amended soil by the SEC-ICPAES system showed that Al, Fe and Mn eluted as multiple peaks prior to the bed volume, indicating their presence as complexes with organic ligands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009560
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of aluminium on nodulation of two Stylosanthes species grown in nutrient solution (1982)
    Springer
    Plant and soil 64 (1982), S. 141-152 
    Details
    ISSN: 1573-5036
    Keywords: Aluminium toxicity ; Nodulation ; Stylosanthes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Effects of three solution aluminium concentrations (0, 25 and 100 μM) on nodulation ofStylosanthes hamata andStylosanthes scabra inoculated with Rhizobium CB 756 were studied using nutrient solution culture. Aluminium strongly affected nodulation by delaying nodule appearance and reducing the number and dry weight of nodules in both species. The effects of aluminium toxicity on nodulation were more pronounced inStylosanthes scabra than inStylosanthes hamata. These effects of aluminium on nodulation occurred before any significant effect of aluminium on top growth, root growth or root elongation. A plant transfer experiment suggested that aluminium interfered with root infection and/or nodule initiation in both species. The detrimental effect of aluminium on nodulation appeared to be associated with a reduction in lateral root density, thus decreasing the potential number of sites for root infection and nodule formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184246
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  • 9
    Electronic Resource
    Electronic Resource
    Release characteristics of ion-exchange resins as buffers in low ionic strength nutrient solutions (1993)
    Springer
    Plant and soil 155-156 (1993), S. 239-242 
    Details
    ISSN: 1573-5036
    Keywords: ion-exchange resins ; nutrient solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The use of synthetic ion-exchange resins as buffers of nutrient ions is a potential mechanism for the control of ion concentrations in nutrient solutions. In this study equilibrium constants for two cation exchange resins and three anion exchange resins were determined at 25°C in low ionic strength systems. The measured constants were used to successfully predict the resin combinations required to achieve desired solution equilibrium concentrations. The effectiveness of these resins in buffering solution ion concentrations was evaluated by examining their release characteristics in circulating systems from which aliquots of solution were withdrawn and replaced with deionised water to simulate plant uptake. Buffering of NO3 and SO4 concentrations was effective when manual control of one anion was imposed. The cation resins were ineffective in buffering the concentrations of Ca and Mg with a tendency for the resins to retain most of the Ca and Mg in adsorbed form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025028
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  • 10
    Electronic Resource
    Electronic Resource
    Interspecific differences in aluminium tolerance in relation to root cation-exchange capacity (1992)
    Springer
    Plant and soil 146 (1992), S. 77-82 
    Details
    ISSN: 1573-5036
    Keywords: aluminium genotype ; root cation-exchange capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Genotypic differences in aluminium (Al) tolerance hold considerable promise in overcoming an important limitation to plant growth in acid soils. Little is known, however, about the biochemical basis of such differences. Extracellular properties, particularly low root cation-exchange capacity (CEC), have been associated with Al tolerance, since roots of low CEC adsorb less Al than do those of high CEC. A solution culture study was conducted in which 12 plant species (monocots and dicots) were grown in solution culture of low ionic strength (ca 2 mM) for 8 d at four Al concentrations (0, 16, 28 and 55 μM). The species differed significantly in Al tolerance as shown by differences in root length. Root length relative to that of the same species grown in the absence of Al varied from 6 to 117% at 16 μM Al, and from 6 to 75% at 28 μM Al. Species tolerance of Al was not closely associated with differences in root CEC. Although in some species Al sensitivity was associated with high adsorption of Al during a 10- or 40-min exposure to Al (expressed on a fresh mass or root length basis), this was not a good predictor of Al tolerance across all species studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011998
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