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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Nutrition 13 (1993), S. 539-559 
    ISSN: 0199-9885
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-0867
    Keywords: animal manure ; leaching ; maize ; nitrification inhibitor ; nitrogen recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field experiments with silage maize during eight years on a sandy soil in The Netherlands, showed that dicyandiamide (DCD) addition to autumn-applied cattle slurry retarded nitrification, thus reducing nitrate losses during winter. Spring-applied slurry without DCD, however, was on average associated with even lower losses and higher maize dry matter yields. Economically optimum supplies of mineral N in the upper 0.6 m soil layer in spring (EOSMN), amounted to 130–220 kg ha−1. Year to year variation of EOSMN could not be attributed to crop demand only. According to balance sheet calculations on control plots, apparent N mineralization between years varied from 0.36 to 0.94 kg ha−1 d−1. On average, forty percent of the soil mineral N (SMN) supply in spring, was lost during the growing season. Hence, the amounts of residual soil mineral N (RSMN) were lower than expected. Multiple regression with SMN in spring, N crop uptake and cumulative rainfall as explanatory variables, could account for 79 percent of the variation in RSMN. Postponement of slurry applications to spring and limiting N inputs to economically optimum rates, were insufficient measures to keep the nitrate concentration in groundwater below the EC level for drinking water.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Abstract Starting from a problem of technical interest the universal application of finite element solution technique, broadly used in continuum-mechanics, for a numerical calculation of three-dimensional instationary heat-conduction through inhomogeneous bodies with real boundary-conditions is demonstrated. Two different ways in treating the variation-integral are shown, one of which is a generalization of so-called digital Beuken-model. In the appendix a physical interpretation of the variation-integral is given.
    Notes: Zusammenfassung Ausgehend von einem praxisnahen Beispiel wird allgemein aufgezeigt, wie sich die Methode der finiten Elemente, die in der Kontinuumsmechanik bereits weit verbreitet ist, auch zur numerischen Lösung instationärer dreidimensionaler Wärmeleitvorgänge in inhomogenen Körpern mit beliebigen Randbedingungen heranziehen läßt. Es werden zwei Wege zur Auswertung des Variationsintegrals gewiesen, deren einer eine Verallgemeinerung des sogenannten digitalen Beukenmodells darstellt. Im Anhang wird eine physikalische Interpretation des Variationsintegrales gegeben.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5036
    Keywords: manure ; mineralization ; modelling ; nitrogen ; organic matter ; slurry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A computer simulation model of the turnover of organic matter in soil was adapted to simulate the change in soil organic C and N contents of soil during several years following annual additions of farm slurry to maize fields. The model proved successful in estimating the build-up of both C and N in soil and the leaching of N to ground-water in response to applications of slurry ranging from 50 to 300 tons per hectare per year. The model was then used to estimate the build-up of organic matter in soil under crops of fodder maize that were grown using the excess of manure produced during the last 20 years in the Netherlands. The build-up of organic matter from these applications was estimated to lead to about 70 kg extra nitrogen mineralized ha-1 yr-1. As a result of legislation manure applications have decreased and are expected to decrease further in the immediate future. Calculations suggest that after 10 years of manure applied at rates no longer exceeding the amount needed to replace the phosphorus removed by crops, the extra mineralization of N will still be between 45 and 60 kg ha-1 yr-1. If manure applications cease altogether then the extra mineralization will be about 25–30 kg N ha-1 yr-1.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 42 (1970), S. 1373-1376 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mit den Methoden der konformen Abbildung wird analytisch eine Näherungsgleichung abgeleitet, die es gestattet, den Wärmewiderstand bei der Abführung der Friktionswärme in peripher durchbohrten Misch- und Refinerwalzen vorauszuberechnen. Damit wird es möglich, die Zahl der sehr teuren peripheren Bohrungen auf ein Mindestmaß zu beschränken.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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