H. Krug, H.-P. Liebig
Following the approach of planning model development the reactions of lettuce transplants to radiation and temperature were tested in greenhouses, using constant day and night set points for heating.

Transplant growth can be described by an exponential function, if sowings from November to middle of December are excluded. The extended Feldmann function fits for sowings during the total season and is more universal. Using this growth function, via response surfaces (fig. 1) the output of the planning model (fig. 2) can be calculated.

The planning model allows for estimating the effect of season and set point on

  • timing (sowing or planting date) as a function of season and temperature set point
  • the effect of growth promoting procedures (fig. 3)
  • the variation of the transplant period as a function of the weather conditions in particular years (fig. 4)
  • the energy (and CO2) demand (fig. 5).
Krug, H. and Liebig, H.-P. (1989). PRODUCTION PLANNING - TRANSPLANT PERIOD (EMERGENCE TO TRANSPLANT SIZE). Acta Hortic. 248, 175-180
DOI: 10.17660/ActaHortic.1989.248.19

Acta Horticulturae