When asking: “How can a system with a controlled environment help improve crop performance?”, the answer is easy… The more you analyze data and control CEA variables inside of your system, the better your crop will perform.
In order to obtain all the benefits from CEA systems, it’s important to understand plant physiology.
In this article we will cover and summarize the most important information about CEA variables: Why are they important and how can you use them to improve your plant performance.
Temperature is a very important variable inside a growing system. Temperature is a variable that can directly affect plant growth and development. This variable has a direct response in plant metabolism. When the temperature is higher than the recommended levels we will notice an increase in metabolism, the plant will start to develop more quickly. On the other hand, low-temperature levels can reduce plant metabolism. When plant metabolism is slower than usual your product can take more time to be ready to harvest.
The most important aspect of plant response to temperature is to understand the response to plants to the average daily temperature. When growing plants we will always look up to maintain the recommended temperature levels. However, recognizing plants respond to the average daily temperature, you can work inside your system in order to maintain the AVERAGE DAILY temperature within the recommended levels. Meaning you can have some fluctuations and be more flexible inside your growing systems. Applying this knowledge will help you to promote good growth and development in your plants and improve efficiency in greenhouse management.
We know air circulation inside our growing system is very important to keep a uniform ambient. However, airflow can have more important functions. Airflow is also related to the process of photosynthesis and transpiration. By keeping ideal conditions of airspeed inside your system you will allow your plants to have good gas exchange and transpiration. When transpiration is affected, uptake of passive nutrients such as Calcium can be reduced. A clear example of this is the presence of tip burn in greenhouse lettuce. Tip burn in lettuce is most of the time, triggered by insufficient airflow over the leaf surface. Bad airflow will create the boundary layer. A resistance placed over the leaf directly affecting stomata behavior. Is recommended to keep airspeed over the leaf surface between 0.3 to 1 m/s.
Relative humidity refers to the amount of water vapor in the air as compared with the amount of water that the air could hold. Humidity levels are important to promote plant health. Humidity is good for plants! However, we need to avoid high humidity levels that can trigger fungi growth, affect pollination and nutrient uptake. On the other hand, low humidity levels will cause stress in stomata behavior. Under low humidity levels stomata tends to close in order to avoid losing water. As a result plant uptake and photosynthesis will be affected.
|CROP||Recommended humidity levels|
|Lettuce||50% – 70%|
Reproductive: 40% – 50%
|Microgreens||50% – 60%|
Carbon dioxide is an essential molecule for photosynthesis. Ambient levels of CO2 are around 400 ppm. Ambient levels of CO2 can be enough the keep good growth and development in crops. But we also know CO2 enrichment can be used in order to optimize plant performance. Research has demonstrated that CO2 enrichment can increase yield from 14% to 45% in common crops. In order to obtain the benefits of CO2 enrichment levels should be increased to above 800 ppm (crop specific).
Light is one of the most important factors growing any crop. But, how can you know if your crop is receiving enough light? There is one way to measure light intensity in plants. Light itself can occupies a large fraction in electromagnetic spectrum. But just a fraction of the spectrum is utilized by plants to make photosynthesis. This section of the light spectrum from 400 nm to 700 nm is called Photosynthetic Active Radiation (PAR) and can be measured in mmol m-2 s-1 (Photosynthetic Photon Flux Density, PPFD). PAR will provide us the amount of light particles that plants are receiving per area in a fraction of one second.
In order to understand and evaluate the quantity of light your plants are getting, we use Daily Light Integral (DLI). A cumulative version of PAR where we can measure the quantity of light received by plants per area, per day (mol m-2 d-1). Many studies have been done evaluating crop performance under different DLI levels. This knowledge allows us to determine if levels of light in our greenhouse or indoor farm are enough to have good production. By understanding how plants respond to light you can have better management of your system. For example, you can decide to eliminate light when light levels are above de optimum and radiation from light is heating your system. On the other hand, when natural light levels are below the needs you can then evaluate the need for supplemental lighting.
Remember the more you measure and the more you understand plant response to CEA variables the more control you will have in your system to optimize plant performance.
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