Tab. 4: Chamber settings according to greenhouse computer

4.1.2 Chamber settings

The settings in the chambers were regularly recorded. Table 4 shows the average of the air temperature, floor temperature, CO2 amount, windows opening and humidity.

The average air temperature amounted around 21°C and was very similar between the light treatments. The average air temperature during the day was about 0,5°C lower in the treatment “HPS” compared to the other light treatments. However, the average night temperature was similar between light treatments.

The floor temperature during the day was comparable between the light treatments. The floor temperature during the night was less than 3°C lower in the treatment “HPS” compared to the other treatments.

The mean CO2 amount was very similar between treatments. Windows were in all light treatments most of the time closed. Humidity amounted 61-68%.

Tab. 4: Chamber settings according to greenhouse computer.

Greenhouse computer data (Average over the experimental period) HPS Hybrid high Hybrid

Air temperature (°C) 21,1 21,3 21,5 day (°C) 22,4 22,8 23,0 night (°C) 18,6 18,6 18,7 Floor temperature day (°C) 42,4 42,2 41,6 Floor temperature night (°C) 34,4 36,9 37,2 CO2 (ppm) 740 747 761 Windows opening 1 (%) 1,8 2,0 3,6 Windows opening 2 (%) 1,6 2,3 2,1 Humidity (%) 66 61 68

4.1.3 Substrate temperature

Substrate temperature was measured weekly at low solar radiation at around noon and fluctuated between 18-23°C. Substrate temperature was on average significantly lower in “Hybrid high” compared to the other light treatments. On average amounted this difference 0,6°C (Fig. 3).