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  • 1
    ISSN: 1573-5036
    Keywords: chemical compounds ; field and pot trials ; mathematical optimization model ; mineral nutrients ; potato ; Solanum tuberosum L. ; threshold values ; tuber yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Data of yield characteristics and the main chemical compounds of potato tubers, received from special NPK-fertilized pot and field trials, were individually evaluated by multiple regression analysis. The best suited mathematical functions, including linear, quadratic and interactive terms of N-, P- and K-concentrations in tuber dry matter, were integrated as independent variables into the models and the SUMT-method was applied for the nonlinear programming. Particular nutrient requirements could be derived from different NPK-ratios which were obtained by optimization. These ratios led to maximum tuber yield (=objective function) while at the same time observing special threshold values (e.g. nitrate) or limiting indices (=constraints) of tuber quality. By means of simulation it was possible to demonstrate characteristic differences between the effect of N-fertilization and varied N-concentrations on tuber yield and composition. Calculation of dependent variables by fixed NPK-ratios of the tubers resulted in excellent correspondence of the values for several parameters with the predictions made by both models, which were based on pot or field experiments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; NPK nutrition ; tuber weight losses ; chemical composition changes ; vitamin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Empirical mathematical models are described for calculating the effects of varying supplies of nitrogen, phosphorus and potassium on pot and field grown tubers. Through optimization and simulation, potato tuber fresh and dry weight losses and chemical composition changes (ascorbic acid, citric acid, glucose, fructose, sucrose, nitrate) are calculated over a 6-month period of storage at 4°C. The effects of variation in single nutrients as well as of increasing N fertilization on storage are calculated. Calculations giving the maximum vitamin C content at harvest and after storage indicate the nutrient supply required.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; reducing sugars ; sucrose ; ascorbic acid ; citric acid ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pot and field experiments were carried out to test fertilizer treatments on the behaviour of potato tubers stores at 4°C and ≥90% relative humidity for 6 months. Weight losses (separated into water and dry matter) were enhanced after N and K fertilization and decreased by increasing P supply. Glucose and fructose contents were reduced at harvest by high N-fertilizer rates compared to no or low fertilization, but throughout storage reducing sugar accumulation was increased, sucrose reduction was decreased and ascorbic acid was increased. K fertilization affected the chemical composition of the tubers somewhat similar to that of nitrogen fertilization. High initial nitrate content of the tubers seemed to be increased and low nitrate values were decreased during storage. The tubers from pot experiments showed similar changes but of greater magnitude.
    Type of Medium: Electronic Resource
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