(UK tekst)
Carbon dioxide fertilization can be used to enhance the growth of cucumber, tomato and salad.
The carbon dioxide concentration in normal air, 340 ppm, is not sufficient for producing the best yield. Plants usually require carbon dioxide concentrations between 600 and 1,000 ppm. Supplementary carbon dioxide is particularly important when using artificial lighting. If the concentration of carbon dioxide is allowed to fall, growth is halted, and artificial lighting provides no benefits.
When extra carbon dioxide is added into greenhouse air, tomatoes, cucumbers and salad yield up to 25-30% more harvest, and there is some evidence of even greater percentages. Cut flowers and potted plants also benefit from carbon dioxide fertilization. Carbon dioxide not only increases yield, but also makes harvest earlier and improves the plants’ resistance to disease and pests.
Carnations can bloom up to one month earlier. Salad is ready for harvest weeks earlier and tomatoes in tomato sprouts might ripen 1 week earlier. Several studies and practical experience clearly indicate that carbon dioxide fertilization pays off.
In greenhouses heated by burning propane, carbon dioxide is obtained as a by-product, but often at the wrong time of day. Carbon dioxide is needed most at midday when extra heat is seldom needed. The heating system must be able to store the heat and release it during the cold hours of the day. There is always a risk for incomplete burning resulting in formation of NOX which is very harmful for the plants.
If the greenhouse heating system cannot store heat, the best solution is usually to add pure carbon dioxide in the greenhouse air. This also helps to avoid moisture problems produced by burning propane. One kilogram of propane generates 1.6 kilograms of water vapor, which condenses into liquid water. And the water won’t go away by itself.