STATIC REGRESSION MODELS FOR PLANNING GREENHOUSE PRODUCTION
Using a non-linear regression function with multiplicative terms (fig. 2), response surfaces were calculated which allow to derive mean growth rates and thereby growth periods as a function of irridiance and temperature (fig. 3 for lettuce transplants with different set points for heating) and possibly CO2-concentration, as a function of weight at transplanting, of weight at harvesting and of the season with special or long term weather conditions.
This model allows to derive:
- Dates of emergence or planting and harvesting, respectively, as a function of the season and the set points for heating (fig. 3) and possibly CO2 -concentration, based on mean long term weather conditions or the weather of a particular year.
Examples for lettuce transplants in fig. 3: Planting date March 15., using set points of 14/10° C (day/night) emergence at beginning of February, for set points of 2/2° C at the middle of November. Or with emergence middle of November transplant size is reached using set points of 14/10° C at beginning of February and for set points of 2/2° C at middle of March.
- The variability of the growth period as a function of the weather conditions of a particular year and the set point of heating (fig. 4) or other growth promoting procedures. This implies the risk of planning.