Garden & Greenhouse


Using Climate Controllers to Increase Yields

Posted December 23rd, 2009 by Robin Nichols in

GraphiqueThere are good reasons to choose indoor or greenhouse gardening and the most interesting one is probably defying and overcoming Mother Nature to manage climate conditions for faster growth and increased yields. Some gardeners choose to manually manage the garden’s climate parameters, but others prefer using climate controllers, so they can have a more precise growing environment. But using controllers will have positive effects only if the user understands the plant’s climate related needs..

Temperature: The Most Important Climate Parameter

Temperature directly influences many aspects of the plant’s development, such as photosynthesis and
cellular respiration. The temperature affects these development processes by improving or limiting the tissues’ growth and the cells’ division. Some phenomena are also triggered at a certain temperature level like dormancy, blooming and seed germination. To simplify, temperature influences directly the harvest’s quality as well as the yield.

Each plant species has an interval of temperature within which the growth is optimal. To complicate things a little, this interval can change in time, even for the same plant. Many factors are involved, some belong specifically to plants, like the age and the growing stage, and others are external to the plants, like the climate conditions. For example, the optimal temperature diminishes according to the plant’s age but raises with high luminosity or high CO2 concentration.

Humidity’s Impact on Transpiration

One of the humidity’s most significant impacts is its considerable influence on plant’s transpiration, a very important mechanism. In fact, transpiration, meaning a loss of water vapor from the stomas, creates the necessary suction to transport the water in the plant and draw water and nutrients through the roots. A high humidity level reduces the transpiration process as well as the absorption and circulation of water and nutrients. So, even if all the other conditions are perfect, it results in a reduction of the photosynthesis process and the growth.

A low humidity level also brings different problems, particularly an important transpiration which might lead to the plant’s wilting and death. To protect itself, the plant closes the stomas and the photosynthesis process is stopped.

Optimal CO2 Concentration for Maximum Photosynthesis

In nature, the average CO2 proportion in the air is approximately 400 parts per million (ppm) but can largely vary depending on natural or human made CO2 production. The air in the garden should minimally be around this concentration. If it is below this limit, photosynthesis and growth considerably slow down and might even stop around 200 ppm or less. This situation might happen in an airtight indoor garden with no CO2 added. The plant will then consume the ambient CO2 until it’s all gone.

The CO2 is an important element in the photosynthesis process, directly responsible for the plants’ growth. If we don’t take water in consideration, the plant is principally composed of carbon (C) and oxygen (O), which mainly come from CO2. During photosynthesis, the CO2 in the air is sort of “captured” by the plant powered by the light energy. So when the CO2 concentration in the air is increased, the photosynthesis process and the growth increase as well. In other words, plants feed themselves with CO2 and use it to fabricate tissues. The more plants eat, the bigger they get.

The vast majority of plants are comfortable with concentrations varying between 700 ppm and 1000 ppm during the day (light period) and around 400 ppm at night (dark period). These ideal conditions are different from day to night because the photosynthesis process happens only in presence of light. The CO2 enrichment is then necessary only in presence of light and therefore is useless, even harmful, in the dark period.

CO2 Concentrations Effects on Plants

Concentration (ppm) Effects
200 and less To avoid – photosynthesis and growth interruption
Near 400 Daytime minimal recommendation

Nightime recommended concentration

Between 700 and 1000 Average concentration recommended during daytime
1500 and more To avoid – useless, non profitable and harmful to crops

In order to provide the plants with the best CO2 concentration for their growth, many gardeners use CO2 enrichment. Not only will it improve yields result, but maintaining the recommended CO2 concentration in the air will also have the advantages of reducing the production time, accelerating flowering, improving the quality and the quantity of fruits and flowers, and it may even decrease the incidence of some pathogenic fungus.

Ideal Temperature, Relative Humidity and CO2 Concentration Level for Day and Night

In nature plants are submitted to a variable climate between day and night. That’s why they generally need different temperature and humidity levels for light and dark periods. For good development, most species prefer a temperature that is a few degrees lower at night than during the day.

The appropriate CO2 concentration is also different from day to night for different species. As explained earlier, CO2 is not required during the night (or dark period) as photosynthesis is suspended without light. The following table presents day and night ideal conditions for different plants variety.

Plant Tº – day (ºC) Tº – night (ºC) RH – day (%) RH – night (%) CO2 – day (ppm) CO2 – night (ppm)
Tomato 21-25 15-18 60-80 ~70 1000 400
Cucumber 22-28 19-22 65-85 65-85 1200 400
Lettuce 14-18 10-13 60-85 60-85 1000-1500 400
Roses 18-24 16-17 50-60 40-60 1000-1200 400

Climate Controllers: A Must to Combine Precision and Simplicity

Some gardeners choose to manually control climate parameters, but they quickly realize that this method can require a lot of manipulations and, at the end, may not be precise.

Gardening with climate controllers is simple: with built-in sensors to measure the ambient temperature,
relative humidity or CO2 concentration, they activate the appropriate equipment when the climate conditions are different than the ones programmed in the controller. They are also a beneficial investment allowing better harvest with high quality and increased yields. In order to fulfill and respond precisely to the plants’ needs, some controllers allow the gardener to choose different settings for light and dark periods (day/night). The controllers with a built-in light sensor simplify their programming: the light activates the day set points while the absence of light activates the night set points. This eliminates programming errors related to timing devices.

It can also be effective to use a combined controller that simultaneously controls more than one climate parameter and intelligently manages many types of equipment. In addition to improving the climate stability, this type of controller also allows for a better use of the equipments’ combinations. Most importantly, the controller simultaneously manages climate parameters that influence each other, like temperature and humidity, but also the CO2 concentration (carbon dioxide) which has a major impact on yield.

Keeping these features in mind and understanding a plant’s climate related needs will help you select the right controller for your garden.

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