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How to Accurately Measure Light for Plants Using Daily Light Integral (DLI)

How to Accurately Measure Light for Plants Using Daily Light Integral (DLI)

Introduction

Aroids, with their striking foliage, are a prized possession for any collector. When it comes to growing aroids indoors, artificial lighting plays a crucial role. However, there is very little literature out there for advanced hobbyists that need more information other than basic advice. Understanding and accurately measuring light through Daily Light Integral (DLI) can significantly impact the growth and health of your aroids. This blog post delves into the science of DLI and how you can use it to create an optimal environment for your aroids.

What is Daily Light Integral (DLI)?

DLI is a measure of the number of photosynthetically active photons (particles of light in the 400-700nm range) received by a specific area in one day. It is expressed in moles of light per square meter per day (mol/m²/d) and is crucial for assessing whether your plants are receiving the light they need for photosynthesis.

Why LUX and Foot-candles are Not Accurate for Plants

LUX measures the amount of light in lumens per square meter, while foot-candles measure the amount of light in lumens per square foot.

  1. Not Specific to Plant Growth: LUX and foot-candles are general measurements of light intensity and do not take into account the specific wavelengths of light that are used by plants for photosynthesis.

  2. Human-centric Measurements: Both LUX and foot-candles are based on how humans perceive light, not how plants use light. They give more weight to the yellow and green parts of the spectrum, which are less important for plant growth.

  3. Lack of Daily Accumulation: Unlike DLI, LUX and foot-candles do not account for the cumulative amount of light that plants receive throughout the day, which is crucial for understanding how much energy plants have for growth.

Why is DLI Important for Aroids?

Aroids, like other plants, require a certain amount of light to thrive. Too little light can lead to elongated, weak growth, while too much can cause leaf burn. DLI helps you quantify the light your aroids are receiving, allowing you to adjust accordingly.

Measuring DLI for Aroids

Step 1: Understand Your Aroids’ DLI Requirements

Different aroids have different DLI requirements. For example, Monstera deliciosa typically requires a DLI of 4-6 mol/m²/d, while dark and velvety Anthuriums might need slightly less. Research the DLI requirements of the aroids in your collection.

Step 2: Measure the Current DLI

Use a quantum sensor to measure the photosynthetic photon flux density (PPFD), which tells you how many photosynthetically active photons are hitting a specific area every second. Take measurements at different times of the day to calculate the average PPFD.

Step 3: Calculate DLI

Multiply the average PPFD by the number of seconds of light in a day, and then divide by 1,000,000 to convert micromoles to moles.

DLI (mol/m²/d) = (Average PPFD (μmol/m²/s) x Photoperiod (s)) / 1,000,000

Step 4: Adjust Lighting As Necessary

Compare the calculated DLI with the DLI requirements of your aroids. If the DLI is too low, you may need to move the plants closer to the light source or increase the photoperiod. If it’s too high, do the opposite.



Tips for Using Artificial Lighting

1. Choose the Right Lights

Selecting the appropriate artificial lights is critical. LED grow lights are highly recommended as they are energy-efficient and have a long lifespan. Additionally, they emit less heat, which is beneficial in preventing leaf scorch.

2. Control the Spectrum

Different stages of plant growth may require different light spectrums. For instance, blue light is beneficial for leafy growth, while red light is ideal for flowering. Some advanced LED lights allow you to control the spectrum, which can be very beneficial for aroids.

3. Monitor Light Distance and Intensity

The intensity of light decreases as the distance from the source increases. Keep your aroids at an optimal distance from the light source. Adjustable lights can be very handy as they allow you to change the height as your plants grow.

4. Control the Photoperiod

Using timers to control the photoperiod is essential. Aroids typically require a certain number of hours of light per day. By using timers, you can simulate a natural day/night cycle, which is crucial for the plant's circadian rhythms.

5. Use Reflective Materials

To maximize light efficiency, consider using reflective materials around your growing area. This will help to ensure that as much light as possible is directed towards your plants, rather than being absorbed by walls or other surfaces.

6. Monitor Temperature

While focusing on light, it’s also important to monitor the temperature. Some lights can emit heat that can affect the growing environment. Ensure that the temperature stays within the optimal range for your aroids.

7. Calibrate Your Sensors

If you are using sensors to measure light levels, make sure they are calibrated and placed at the right height. This will ensure that you are getting accurate readings.

8. Regularly Clean Light Fixtures

Dust and dirt can accumulate on light fixtures, reducing their efficiency. Regularly cleaning the fixtures can ensure that your plants receive the maximum amount of light.

9. Experiment with Light Recipes

Advanced growers can experiment with different light recipes. This involves varying the spectrum, intensity, and photoperiod to find the optimal conditions for specific aroids.

10. Observe and Adjust

Pay close attention to how your aroids respond to the lighting. Signs of stress, such as yellowing leaves or stunted growth, might indicate that adjustments are needed. Don’t be afraid to tweak your setup based on your observations.

 

Conclusion

Accurately measuring light through DLI is an essential skill for growing aroids under artificial lighting. DLI takes into account the specific wavelengths of light that plants use for photosynthesis and provides a cumulative measure of daily light exposure. By understanding your aroids’ DLI requirements and employing the tips outlined above, you can create an environment conducive to the lush and healthy growth of your plants. Remember that growing plants is both an art and a science, and sometimes the best teacher is experience.

Happy Growing!

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