ISHS Acta Horticulturae 97: VI Symposium on Horticultural Economics
AN ECOLOGICAL PRODUCTION MODEL AS A BASE FOR ECONOMIC CALCULATIONS |
| Authors: | H. Krug, H.-P. Liebig |
| Abstract:
A descriptive production model consisting of three submodels (habitat-, growth- and rudimentary economic submodel) has been developed. With this model the growth rates from emergence to the harvest stage of vegetable species are related to the radiation and temperature conditions inside the greenhouses. For long year weather conditions the growth periods are calculated as a function of the data of emergence (planting) or harvest and the set points of the heating system which allow to calculate the energy costs (data of Vickermann). The yields are calculated as a function of the season and set point. Multiplying the yields by the product prices the output is obtained. The term output - energy costs is considered to be a valuable criterion for planning and estimating the profitability of crops. Furthermore the model permits to calculate the consequences of technical arrangements, as for example double sheltering. Calculations for planning the profitability of crops, production procedures or rotations are only as reliable as the basic data used. And here we have a large uncertainty, according to the complexity of the system with different crops, different varieties, different climates, different seasons etc. This in particular became evident at the time of the energy crisis, when nobody knew the effect of decreasing temperature in greenhouses on the growth period, the yield or the profit. We are trying to overcome these difficulties by quantifying the system plant production in greenhouses, using a descriptive production model (fig. 1). This production model consists of 3 submodels: | |
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