The fiberboard box that I’m using to grow my marijuana plants is 6 feet high with dimensions of 5’ x 5’ for a total square footage of 25. The box is open at the top, but is covered with a fiber mesh. There’s a front door and bottom vents in the rear of the box that have 4-inch blade fans to suck in some fresh air. The walls of the box are lined with aluminum foil to reflect the light from the 1,000-watt HPS horizontal lamp mounted above. Would using CO2 be beneficial for my marijuana plants?
Yes, for two reasons. Increased CO2 will augment the rate of photosynthesis, which will shorten times between harvests and increase yields. Secondly, the CO2 would provide the marijuana plants a higher tolerance to warmer temperatures.
Insert the CO2 below the canopy and let it get pulled through the canopy by rising air. Because of the consistent ventilation, you might end up losing a lot of CO2, but the cost-benefit ratio still remains in your favor. You can improve the system simply by switching to an air-cooled reflector and thermostat-controlled fans.