GROWTH AND YIELD MODELS AS AN AID FOR DECISION MAKING IN PROTECTED CROP PRODUCTION CONTROL

Depending on the special task for planning, control or on-line control of production plant growth has to be simulated with different time steps. If plant growth is measured only several times during its ontogeny and growth functions are used a dynamic growth model with time steps of one day may be developed. Three different procedures are presented:

1. Estimation of parameter values of a growth function from their relation to growth factors.
2. Estimation of daily (24h) growth rates for different growth phases as a function of growth factor intensity.
3. Estimation of daily (24h) growth rates by a function including time and growth factors as input variables.

Essential for these 3 procedures is the assumption that time course of growth is predominantly determined by long term trends. Deviations from this may be described quantitatively by secondary equations. There seems to be a strong correlation between the model and its precision for the whole simulation period. The smaller the time steps of the model are the more detailed research including growth processes is needed. The longer time steps of the model may be the more predominates the simplicity of the model and by that its reduction in estimation errors.