Why CO2 levels are controlled at night
Low cost technology is now available to growers to automatically detect, monitor and control CO2 levels in grow rooms, greenhouses and glasshouses. Broadly, the technology available today allows growers to take one of two approaches to artificially increase atmospheric CO2 around their plants: the continuous approach or the day/night approach.
The continuous approach constantly maintains CO2 at a level during both the day and night. For example, a CO2 level controller sets CO2 to a pre-defined minimum and maximum level (e.g. 1,200 to 1,500 parts per million [ppm]) and opens or closes a valve to a CO2 gas cylinder when these pre-defined levels are reached.
The day/night approach only provides additional CO2 from a gas cylinder during daylight hours. For example, a day/night CO2 level controller acts as a continuous CO2 level controller, as described above, during the day. But at night, the valve to the CO2 cylinder is always turned off. A day/night CO2 level controller has an inbuilt light sensor that can detect whether it is day or night and switches on/off accordingly.
The justification for not providing additional CO2 for plants during the night is that plants only require CO2 during the day for photosynthesis. At night, there is little or no photosynthesis and, therefore, there is no reason why CO2 should be maintained at artificially elevated levels.
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