Demystifying DLI (Daily Light Interval)

DLI (Daily Light Integral) is a popular topic in plant care recently, but what is it? And why should you care? Understanding DLI and how to apply it to your plant care routine can be a powerful tool in promoting healthy plant growth and development. 

However, the concept of DLI can be complex and intimidating, so your friendly neighborhood Krado scientist is here to help demystify DLI. In this article, I will break down the key concepts, provide practical tips for how to use DLI to optimize your plant care, and help you figure out the best way to incorporate DLI into your daily plant care routine.

What is DLI and why should you care?

DLI or “Daily Light Integral” is a measure of the total amount of light that a plant receives over a 24-hour period, usually expressed in units of mol/m²/day. It takes into account both the intensity and duration of the light. This is a fancy way of saying how much light a plant needs to grow healthy and strong each day. Just like how you need to eat food every day, plants need a certain amount of light to grow properly.

What to know about DLI (daily light integral) in relation to your daily plant care routine

It may feel overwhelming trying to understand how DLI fits into your plant care routine, so we’ve compiled some helpful information about Daily Light Integral. Understanding DLI in relation to your daily plant care can help you provide the right amount and quality of light to your plants, leading to healthier and more beautiful plants.

DLI for Optimal Plant Growth

Different plants have different DLI requirements. This can be based on species or even growth stage. By measuring the DLI, you can adjust the amount of lighting your plant needs each day, improving plant growth.

How to Measure & Monitor DLI

To calculate DLI, you would need to use PAR (Photosynthetically Active Radiation) and PPFD (Photosynthetic Photon Flux Density) measurements. You can learn more about that and the tools used in our article PAR vs PPFD.

Using DLI Data

You can use DLI data to adjust lighting schedules, intensity, and duration to optimize plant growth. This may involve increasing or decreasing the duration of light exposure, or adjusting the distance between your plants and the light source.

Okay, but how do I do this?

You have a few options for how you can analyze DLI–manual or through a speciality sensor. Manually analyzing DLI data involves examining the light levels that your plants are receiving over a 24-hour period, and comparing those levels to the optimal DLI requirements for your plants. It looks like this:

  1. Collect DLI data: Collect DLI data over a 24-hour period at different times of day to get a full picture of the light levels.
  2. Calculate DLI: Calculate the DLI by adding up the total amount of light that your plants received over the 24-hour period, and divide that number by the number of hours in the day. For example, if your plants received 10 moles of light per square meter over a 24-hour period, the DLI would be 10/24 = 0.42 moles/m²/day.
  3. Compare to optimal DLI: Look up the optimal DLI requirements for your plant species and growth stage. Compare the DLI that you calculated to the optimal DLI to determine if your plants are receiving enough light or if you need to adjust your lighting.
  4. Adjust lighting as needed: Based on your analysis, you may need to adjust your lighting to achieve the optimal DLI for your plants. This may involve increasing or decreasing the duration of light exposure, adjusting the distance between your plants and the light source, or changing the intensity of the light.

If that sounds too intense, you can get a speciality sensor like Leaflet to do it for you automatically. Leaflet uses the DLI data we gather from your plant to automatically optimize and adjust your plant care routine. Leaflet also gathers additional plant health data–temperature, moisture, and humidity–to account for limitations of DLI (as explained below) to create a truly holistic view of your plant health. Need more light? Less light? We’ll let you know, so you don’t have to worry.

You can also learn more about the science behind light sensors, how to choose your sensor, and where to buy them in Sensors 101.

Limitations of DLI

Quality & Intensity of Light

DLI only measures the quantity of light received by a plant, but not the quality. Different wavelengths of light have different effects on plant growth and development, and DLI does not provide information on the specific wavelengths of light that a plant receives. 

These limitations are why Leaflet has both an AgTech grade PAR Meter and Spectrometer. Leaflet can distinguish both indirect and direct light, intensity and quality, as well as the visible and infrared spectrum. Leaflet is also calibrated to measure the number of photons, improving data accuracy.

Environmental Conditions & Variability 

DLI is also affected by environmental factors such as cloud cover, air temperature, and humidity. These factors can change throughout the day and can lead to fluctuations in DLI, which may not accurately reflect the light conditions experienced by the plant.

DLI is also only one variable, light, and doesn’t account for other factors such as temperature, humidity, and soil moisture. 

These two limitations are why leaflet measures more than one variable, and takes that into account when providing you advice for how to care for your plant.  

Learn more about how the leaflet sensor measures four plant health variables (humidity, temperature, light, and moisture) to give a holistic view of plant health in Sensors 101.

Q & A for DLI (Daily Light Integral)

Why is DLI so popular?

You may have heard DLI (Daily Light Integral) come up because as plants become more popular, plant owners are increasingly turning to scientific metrics to optimize their plant care.

Additionally, advances in LED lighting technology and indoor growing systems have made it easier to control and manipulate light levels for plants, which has increased interest in understanding DLI and its implications for plant growth.

What is the difference between DLI and PPFD?

DLI (Daily Light Integral) and PPFD (Photosynthetic Photon Flux Density) are both measurements used to quantify the amount of light available to plants for photosynthesis, but they measure different aspects of light. To calculate DLI you need to know the PPFD values.

DLI tells you how much light a plant gets in a whole day, and PPFD tells you how much light a plant gets at one moment. 

How do you calculate DLI (Daily Light Integral)?

To manually calculate DLI (Daily Light Integral), you need to know the PPFD (Photosynthetic Photon Flux Density) values for the light source(s) and the duration of the light period in a day. 

This is the formula to calculate DLI: DLI = PPFD × Daily Light Integral Hours (DLIH)


    •    PPFD is the Photosynthetic Photon Flux Density, measured in µmol/m²/s

    •    DLIH is the number of light hours in a day

You may find it easier to use a device that calculates DLI for you. Learn more about those in Sensors 101.

What is the optimal DLI (Daily Light Integral) for plant growth?

The optimal DLI (Daily Light Integral) for plant growth varies depending on the type of plant being grown and the growth stage of the plant. Speciality sensors can be used to measure the PPFD values and determine the DLI while automatically adjusting your lighting schedule to achieve the optimal DLI for your plants.

Is DLI just a buzzword?

While there are limitations with DLI, no, DLI is not a buzzword. It is a well-established scientific term that is commonly used by researchers, growers, and horticulturists to measure and manage the amount of light that plants receive.



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