Importance of Carbon Dioxide (Co2)
for Healthy Plant Growth
Most of the applied research on greenhouse crops has dealt
with effects of environmental conditions on plant growth.
Factors such as water, light, temperature and nutrients are
more easily controlled for optimum growth. It is now possible
to also control and accurately measure Carbon Dioxide
concentrations in greenhouse and Controlled Environment Garden
Carbon Dioxide (CO2) contributes to plant growth as part of
the miracle of nature known as photosynthesis. This enables
plants to combine Carbon Dioxide and water with the aid of
light energy to form sugar. Some of these sugars are converted
into complex compounds that increase dry solid plant
substances for continued growth to final maturity. However,
when the supply of carbon dioxide is cut off, or reduced, the
complex plant cell structure cannot utilize the sun's energy
fully and growth or development is curtailed.
Although carbon dioxide is one of three main components which
combine to produce the products necessary for plant growth,
the amount of carbon dioxide in the air is only 0.03% (250 to
330 parts per million). This compares to 78% nitrogen, 21%
oxygen and 0.97% trace gases in normal air. Numerous tests
have proven that during the winter months carbon dioxide
concentrations inside greenhouses is invariably much lower
than in outside air. This same phenomenon has been shown in
controlled environment gardens.
CARBON DIOXIDE (CO2)
IMPROVES PLANT GROWTH AND QUALITY
Research has shown that in most cases rate of plant growth
under otherwise identical growing conditions is directly
related to carbon dioxide concentration.
The amount of carbon dioxide a plant requires to grow may vary
from plant to plant, but tests show that most plants will stop
growing when the CO2 level decreases below 150 ppm. Even at
220 ppm, a slow-down in plant growth is significantly
Colorado State University conducted tests with carnations and
other flowers in controlled CO2 atmospheres ranging from 200
to 550 ppm. The higher CO2 concentrations significantly
increased the rate of formation of dry plant matter, total
flower yield and market value.
CARBON DIOXIDE (CO2)
CUT OPERATING COSTS WHILE INCREASING PRODUCTION
During the winter months, plants near the middle of greenhouse
beds generally do not grow as rapidly as plants at the edge.
Tests have shown CO2 concentration lower in the center of
greenhouses than near the outer walls. Outside air leaking in
through small openings around windows carries enough carbon
dioxide to satisfy requirements of plants at the edge of beds.
The lack of adequate CO2 lowers the average plant yield
quality and market value.
Costly methods of stimulating plant growth, in order to market
them at optimum profit, are presently being used. One of these
is extra heat (with open vents). This, however, increases
operating costs and decreases profit. On the other hand,
growers using CO2 are cutting their heating costs as much as
50% while realizing extra profit from increased crop
RESULTS FROM CO2 ENRICHMENT STUDIES
adding CO2 to the atmosphere around the plant, a 40% crop
increase was achieved. Whereas previous crops averaged 22
heads per basket, lettuce grown in the increased CO2
atmosphere (550 ppm) averaged 16 heads of better quality per
CO2 levels to 550
ppm produced an obvious increase in yield (over 30%), but the
greatest benefits were earlier flowering (up to 2 weeks) with
an increased percentage of dry matter.
The addition of
controlled carbon dioxide provided a remarkable improvement in
blossom quality, number and yield. Plants consistently
produced many more flowers with 24 to 30 inch stems. Average
yield was increased by 39.7%.
Work in experimental stations has shown that crop increases of
as much as 29% have been obtained by increasing the CO2
concentration. More desirable firmness and more