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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 235-250 
    ISSN: 1573-0867
    Schlagwort(e): Zinc fertilizer ; controlled-release
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 251-266 
    ISSN: 1573-0867
    Schlagwort(e): Zinc ; controlled-release ; diffusion ; pH ; temperature ; phosphate ; clay ; sand ; moisture content
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 17 (1988), S. 267-283 
    ISSN: 1573-0867
    Schlagwort(e): Zinc ; controlled-release ; linseed
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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