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 22°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, Hybrid+LED” 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 about 1°C higher in the treatment “HPS, Hybrid+LED” compared to the other treatments.

The mean CO2 amount was 27-44 ppm lower in the treatment “HPS, Hybrid+LED”. However, windows were in all light treatments most of the time closed. Humidity amounted 60-69%.

Tab. 4: Chamber settings according to greenhouse computer.

Greenhouse computer data (Average over the experimental period)

HPS, Hybrid+LED

LED, Hybrid+LED HPS, Hybrid LED, Hybrid

Air temperature (°C) 21,6 22,0 22,3 22,2 day (°C) 22,6 23,1 23,5 23,5 night (°C) 19,4 19,6 19,7 19,5 Floor temperature day (°C) 45,3 44,9 44,8 45,2 Floor temperature night (°C) 34,1 32,9 32,0 33,0 CO2 (ppm) 675 713 702 719 Windows opening 1 (%) 0,2 0,3 0,6 0,6 Windows opening 2 (%) 1,7 2,6 3,5 3,7 Humidity (%) 68 62 60 69

4.1.3 Substrate temperature

Substrate temperature was measured weekly at low solar radiation at around noon and fluctuated between 19-24°C. Substrate temperature was on average significantly lower in “HPS, Hybrid” compared to “LED, Hybrid+LED” and “LED, Hybrid”. On average amounted this difference 0,4°C (Fig. 3).