ISHS Acta Horticulturae 428: Ecological aspects of Vegetable Fertigation in Integrated crop Production in the Field
NITROGEN UPTAKE OF VEGETABLE CROPS ESTIMATED BY MEANS OF SIMPLE MATHEMATICAL MODELS |
| Authors: | C. Feller, M. Fink |
| Keywords: | vegetables, growth, nitrogen uptake, nitrogen content, model |
| Abstract:
One characteristic of the fertilization decision support system N-Expert (Fink and Scharpf, 1992) is the ability to calculate nitrogen fertilizer recommendations for top-dressings at any date during the cultivation period. For this purpose a model of the time-course of growth and nitrogen uptake is needed for all important vegetable crops. This model must be adaptable, e.g. to different growth rates which result from different local climate conditions. A simple mathematical model is presented, which meets these requirements. Data taken from the KNS-system (Lorenz et al., 1989) were fitted by means of non-linear regression to a modified Richard's function. This resulted in a set of regression parameters for vegetable crops. The function can be adapted to farm specific growing conditions by additional input parameters (e.g. expected yield, expected duration of crop growth, date of planting or sowing). Experimental data sets of nitrogen uptake by vegetable crops, developed at different research stations in Germany in the framework of a national project 'N uptake curves', were used for model validation. Measured and estimated data were in good agreement for some crops, but not for others. For example the agreement was good for kohlrabi. | |
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