Ugrow Organic: Humidity & Carbon Dioxide

Ugrow are UK distributors for Metrop products. Information on this page is copyright Metrop 2004.

Humidity

Humidity might be the most under estimated growing factor. The relatively humidity (RH), we use as a unit to measure or change this. Dry air will accelerate the evaporation of fluids from the leaf and moist air will delay this. A plant always has to be able to evaporate some water, in order to retrieve new water from the medium which contains new nutrients.

A plant is almost like a pump working on solar energy. When the RH is too low, the plant will evaporate more then it can absorb and will end up with a grow disorder or even dry out completely. If the humidity is extreme high the plant will eventually cease to grow.

So a balance is very important. Small cuttings do not have a lot of roots so therefore can not absorb a lot of water. To encourage a cutting to achieve maximum growth in the first 3 weeks, you will need an RH of 80%. After that, thru to the 6th week, the optimal RH is 60%. In the 7th week and later we bring down the RH again, but not under 40%. Evaporation under 40% goes very fast and therefore hard for the plant to absorb new fluid. As a reaction the plant will close its skin mouths, which will stop the growth and the blooming. This stop will reduce your harvest.

Important is also the temperature of the humidity. There are systems available to release cold water vapour into the air. A cold mist will reduce plant growth, it is better to use lukewarm water. Hobby growers who do not have the use of a humidifier, should fog their leaves for the first 6 weeks.

Carbonic Gas CO2

In the air we find carbon as CO2. It is generated thru the 'respiration' of plants and animals, a by-product of combustion and the decomposition of organic materials.Botany teaches us that CO2 is made out of water and sugar. From here starch, fat and cell material is generated.

Protein also contains carbon. That is why is it is understandable that the dry material of a plant comprises of 50% carbon. For the build up of plant material, carbon is an important element. The air holds 0.03% carbonic acid, this small amount is however enough.

6H2O + 6CO2-light ->C6H12O6 + 6O2

In other words:
Water + carbon-light -> energy
The more CO2, the more energy a plant makes, provided there is enough water and light. Growers that create a partial vacuum (by large extraction installations and small openings) will by 'thin air' (small amount of CO2) always receive smaller plants unless they improve conditions and equalise the air pressure.