How To Increase The DLI In The Cannabis Grow Room For Better Yields?

Are you looking to shed some light, pun intended, on how to boost your cannabis plant’s yields? When it comes to that, you need to understand the daily light integral or DLI, which measures the amount of light your plant gets in a single day. 

But there’s more to DLI than just this. DLI helps your plant in many ways, and if you want to increase its yields, you need to increase the DLI levels your plant gets. And that’s exactly what we’ll be looking at in this article. Let’s learn about DLI and how to increase it to maximize your plant’s yields. 

What is Daily Light Integral or DLI? 

Let’s start with the basics — what exactly is DLI? Put simply, it is a metric that measures the total amount of photosynthetically active radiation (PAR light) your plant receives in 24 hours. It is calculated as the cumulative photosynthetic photon flux density or PPFD. 

In other words, DLI is essentially the usable light that is available to your cannabis plant daily. Knowing and working with DLI in mind helps your plants receive the right amount of light intensity and duration, promoting better growth. 

So, how does DLI help? It has various effects on your cannabis plant, acting as a crucial factor in healthy growth and yields. Light is essential for your plant’s survival. Let’s look at how ideal DLI levels can help your cannabis plant:

1. Enhanced Photosynthesis

DLI directly affects the rate of photosynthesis, so when plants receive an ideal DLI, their photosynthetic process operates at its peak efficiency, thereby producing the carbohydrates and sugars that are needed for the plants to grow well. 

If you make sure that the plants get adequate DLI, they produce sufficient energy to support growth processes like leaf and stem development, root expansion, and bud formation. This energy is vital for sustaining growth throughout the plant's life cycle.

Also, you may have sometimes noticed your plants growing tall and leggy with weak stems. This usually occurs when they are placed far away from the light or when the light isn't very intense. However, with the right DLI, the space between the internodes can be reduced and the plant can develop a bushy canopy with dense flowers. Plus, there will be lots of buds sites, which is what you really want as it increases the yields dramatically. 

2. More Growth in the Vegetative Stage

During the vegetative stage, cannabis plants focus on developing a solid structure to support the buds later on. A higher DLI at this point is important as it can help the plant develop thick stems that are resilient and don't topple when they have buds. 

The plants will also develop several shoots (which is why it's the perfect time to train the plant) and more branches. The canopy fills up pretty quickly. And, don't forget the roots as the plants certainly don't. Remember, the health of the plant depends on the roots, so the plants strive to develop an extensive root system that makes it easier to absorb nutrients. And when the plants take up all the nutrition they need, they will naturally produce more. With a good root structure, you can also rest assured that the plant is less likely to be invaded by pests as it has a strong defense system. 

3. More Buds and More Resin 

Plants that get adequate DLI during the flowering stage develop lots of buds. Not only are the buds denser but the resin production is also amped up, not to mention how aromatic they smell. 

Needless to say, you're also conserving energy by providing exactly what the plants need. This not only cuts down on electricity expenses but also lessens the environmental impact of your cannabis operation. 

Having the right DLI for your plant can significantly influence nearly every aspect of your plant’s growth, which cumulates into a higher yield. 

How Much DLI Does Cannabis Need?

We’ve already established how important DLI is, but how much do you really need? Let’s take a look at it now. Remember one thing, your cannabis plant needs different DLI levels at various stages of growth — from seedlings to the vegetative phase and ultimately flowering stage.

Ideally, your plant needs the following DLI during different stages of its life:

Seedling Phase: During this stage, cannabis plants are fragile and necessitate a lower DLI to prevent light-induced stress. Thus, you can maintain a light integral (DLI) of approximately 15 to 20 mol/m²/day. You can even make do with 12-15 mol/m²/day to help establish strong root systems rather than focusing on rapid plant growth.

Vegetative stage: Moving into this stage, plants require a DLI range of 20 to 40 mol/m²/day to encourage growth supporting the development of sturdy stems and lush foliage essential for future flowering.

Flowering stage: As plants transition into the flowering stage, their energy needs increase significantly for bud production. To enhance flower development and overall yield, maintain a DLI between 25 to 50 mol/m²/day during this stage.

Remember that apart from maintaining an ideal DLI, you should also focus on environmental factors like temperature, humidity, and CO2 levels that can impact how plants utilize light efficiently. 

In addition, different strains may have varying DLI needs. For instance, indica-dominant strains might thrive with a lower DLI compared to sativa strains that typically require more light.

As the plant grows bigger, its DLI requirements also increase. To ensure your plant gets the right amount of light, you must also measure PPFD, which is the number of PAR photons hitting a specific surface per second. 

Ideally, your plant should receive the following amount of PPFD:

• Vegetative stage: 300 to 600 µmol in 18 hours 
• Flowering stage: 450 to 1000 µmol in 12 hours 

DLI is indicated in mol/m²/day as mentioned above, representing the number of photons within the PAR range (400-700 nm) that reach a meter of plant canopy over a day. The key factors for calculating DLI include:

• Photosynthetic Photon Flux Density (PPFD): This measures the number of photons in the PAR spectrum that hit a meter square per second. It is expressed as micromoles per square meter per second (µmol/m²/s).
• Photoperiod: This denotes how long plants are exposed to light each day measured in hours.

For this, you can either use a PPFD meter or refer to your grow light’s product specifications. You can also roughly translate lux to PPFD using an online calculator, but take the results with a big grain of salt. 

Once you have the PPFD your plant is receiving, you can then calculate the DLI your plant is getting by using the following formula:

• DLI = PPFD x Light Duration (hours) x 3600 / 1,000,000

Here, 3600 refers to the number of seconds in an hour, and 1,000,000 converts micromoles to moles. You can also use DLI calculators, where you simply have to input PPFD and light duration if math isn’t your forte. 

If you don't want to calculate anything at all, here are some tools to measure and track the DLI:

1. Quantum Sensors: These sensors directly measure PPFD by detecting the amount of PAR light reaching the canopy. You can take readings at various times to determine the PPFD and subsequently calculate DLI.
2. DLI Meters: You can get some sophisticated light meters that give you the DLI value immediately. These meters are especially valuable in environments where lighting conditions change throughout the day. Some of them are very expensive and make sense for commercial growers but home growers don't need to use them. Check out Apogee Quantum Meters to find out more if you’re inclined. 
3. Apps: There are software programs and mobile applications specifically designed to estimate DLI based on input factors such as intensity, photoperiod duration, and geographic location. Some examples include Photone and Grow Light Meter. You will need to monitor DLI frequently as there could be some changes in the lighting conditions due to various factors including the deterioration of bulbs, seasonal fluctuations in sunlight, and the growth stages of plants. If you monitor and adjust the DLI daily, your plants receive the best light they need throughout their life cycle. 

Once you calculate the DLI and PPFD for your cannabis plant, you can then start optimizing it. In the following section, we go over how to increase the DLI for bigger yields. 

A Note on Cannabis Photoperiod

Before we proceed, let’s also consider your plant’s photoperiod. To successfully guide your cannabis plant through its life stages, you need to adjust the lighting durations to mimic the natural seasonal rhythms. 

Generally, you want to keep your grow lights on for as long as you can during the growth stage. But when it comes time to bloom, you need to cut down the lighting hours significantly to push the plant into the flowering stage. 

Typically, most growers prefer using an 18/6 light cycle for veggies and 12/12 for bloom. But you can still fine-tune the light hours as per your plant’s needs and growing environment. Still, stick to 16 to 24 hours for vegging plants and 10 to 13 hours for blooming plants — this is the ideal range. 

How To Increase The DLI In The Cannabis Grow Room?

Now let’s look at how you can increase the DLI in your grow room to optimum levels. Here are some methods you can use. 

Remove Anything that Blocks the Light 

If you are growing your cannabis outdoors, start by removing anything that might be blocking the light, including trees or poles. By doing so, you’ll straightaway allow your plant to get more sunlight, which will increase the DLI naturally. 

Do note that if you are growing your cannabis in hot weather, excessive sunlight can cause heat stress. So, be careful you don’t overheat your plant. Sometimes, a bit of shade can benefit your plant. 

Use Supplemental Lighting 

For indoor growers who have already maxed out their primary grow lights, supplemental lighting can be a game-changer. These additional lights enhance your plant's light exposure, ensuring that every part of the canopy receives adequate illumination. 

By strategically placing these lights, you can effectively eliminate any blind spots or areas that might not be receiving enough light, which is crucial for consistent growth and maximizing yields.

However, it's essential to approach supplemental lighting with care. Overexposure in specific areas can create hotspots, leading to heat or light stress on your plants. This stress can negatively impact plant health, so it's vital to monitor light distribution carefully. 

To prevent overheating, consider adding an extra fan to keep the environment cool and stable. 

Increase Photoperiod Hours 

If the DLI isn't meeting your cannabis plant's needs, you can extend the light hours to increase it. By increasing the duration of light exposure, you effectively raise the DLI, allowing your plants to absorb more photons for photosynthesis. 

For instance, some growers opt to keep the lights on 24/7 during the vegetative stage to maximize DLI, promoting faster and more vigorous growth. 

However, it's crucial to approach this method carefully, as an excessively high DLI can stress your plants and lead to issues like light burns or nutrient imbalances. We will get into this in detail later. Always monitor your plants closely to ensure they thrive under the increased light.

Spend Some More on Bigger Lights 

Investing in bigger grow lights is one of the most straightforward ways to boost DLI levels in your grow room. While the initial cost may be high, the long-term benefits — like larger yields and healthier plants — make it a worthwhile investment. 

Quality grow lights ensure your cannabis receives the optimal light intensity needed for robust growth, leading to bigger, denser buds. So, if nothing else works, you can always upgrade your grow lights. 

Use CO2

You’re increasing the DLI to maximize photosynthesis in your plant. Here’s the thing, you can do the same by increasing CO2 if you’ve peaked the DLI of your plants. 

Supplementing your grow space with CO2 can significantly improve your cannabis plants' ability to utilize light. Indoor CO2 levels typically range between 400 to 600 ppm, which can restrict photosynthetic activity. 

By raising CO2 levels to at least 800 ppm, you enable your plants to better process and use the light available to them, leading to more vigorous growth and larger yields. 

For seedlings, maintaining around 400 ppm is ideal; for plants in the vegetative stage, aim for 400 to 800 ppm; and during the flowering stage, increase CO2 levels to between 800 and 1400 ppm. 

This approach ensures that your plants can handle higher levels of PAR light, maximizing their overall growth potential. Just be sure to manage CO2 levels carefully and ensure adequate ventilation to maintain a balanced and healthy environment.

Adjust the Light Spectrum 

Fine-tuning the light spectrum can help the plants as different light wavelengths impact aspects of plant growth, development, and overall yield. You don't have to adjust the spectrum yourself. Instead, get a light that offers these spectrums so you have one light for an entire life cycle. Or, you can use the lights according to the spectrums, depending on the stage of growth. 

The term "light spectrum" refers to a large range of the wavelengths of light that is emitted by a specific source. For plants, the spectrum ranging from around 400 nm (violet) to 700 nm (red) is ideal as it helps with photosynthesis and plant growth more than other spectrums. 

Blue Light (400-500 nm): This type of light is vital during the phase as it supports robust compact growth and fosters lush foliage development. It helps to reduce space between the internodes and maintain a sturdy structure. 

Red Light (600-700 nm): This spectrum helps during flowering as it triggers bud production resulting in increased yields. It also influences stem elongation and you can use it to control the height. 

Far Red Light (700-750 nm): This helps to control the flowering cycle by affecting photoperiodism and can trigger flowering when you use it with red light. 

Green Light (500-600 nm): Although green light isn't as efficient for photosynthesis as red light, it can penetrate the plant canopy supporting photosynthesis in lower leaves and contributing to overall plant health.

Coming to what we mentioned earlier, you can either adjust the spectrum or get a light that encompasses these spectrums for good growth:

Seedling Stage: For seedlings, a balanced spectrum with a higher concentration of blue light is recommended. This helps promote root development and prevents the plants from becoming too tall. 

Vegetative Stage: In this phase, cannabis plants thrive under blue light, fostering vigorous vegetative growth characterized by sturdy stems and lush foliage. However, there should be a higher blue-to-red ratio as it helps the plant prepare for its upcoming blooming phase. 

Flowering stage: During this phase, it is recommended to use a light spectrum consisting of more red light with a mix of blue and green light. At this point, it's great if your lights provide some far-red light as well. 

Use Reflective Surfaces 

Using reflective materials can help the plants use more light and support robust growth and high yields. This can also improve intensity and distribution, allowing even the lower parts of the branches to get more light. These surfaces help redirect light that would otherwise go to waste, ensuring that a greater number of photons reach the plant canopy. One advantage is that you save money and energy as you can provide more light to the plants. However, the effectiveness depends on how you place these materials in your grow room.

Here are a few options you can use:

1. Mylar: Widely favored in grow rooms for its reflectivity of around 90-95%, Mylar is a flexible film. You can fix it to the walls of your grow room/tent, ceilings, and floors. You can either use smooth Mylar or textured ones (diamond Mylar) for uniform light distribution. 
2. Panda Film: Panda film has one side that reflects light while the other side blocks light. The white side reflects 85-90% of light. It's waterproof and easy to maintain, making it a practical choice for many small grow room setups.
3. Matt White Paint: Though less reflective than other types, you can simply paint your grow room with white paint to reduce costs. It also helps to reflect at least 75-85% of light. However, make sure you don't use glossy paint as matt white paint is more effective.  

What Happens if You Increase the DLI Too Much?

As always, too much is too bad so while you should provide the right DLI, you should avoid exceeding the recommended range. High levels of DLI can stress the plants so much that the leaves start getting discolored. You may also notice nutrient deficiencies and lower yields. Here’s a detailed overview of the issues the plants can face:

1. Light stress

When you provide too much light or if the plants are exposed to intense sunlight for a long period, it can lead to photoinhibition where plants struggle to photosynthesize properly due to an overload of light energy. Excessive stress can result in the following effects on plants:

Chlorophyll Breakdown: Too much light exposure can harm the chlorophyll in leaves and they can turn yellow (chlorosis). This impairs the plant's ability to efficiently absorb light, thereby slowing down its growth.

Bleaching: Sometimes, the leaves that are closest to light may lose their color and appear white due to chlorophyll and pigment damage. This indicates that the plant is receiving an excess of light.

2. Dehydration and Heat Stress

Light stress is often accompanied by heat stress as the temperature increases drastically, especially when you're using powerful grow lights like HIDs or if the lights are too close to the plants. 

Due to so much heat, the leaves can curl up and get crispy and the edges may become brown as well. At this point, the plants may increase their transpiration rate in an effort to cool down. But, if the roots cannot keep up with this water loss, it will dehydrate the plants and the leaves will wilt. 

3. Nutrient Imbalances

When plants get excess light, they need more nutrients to keep up with the increased demand. 

As a result, this can cause nutrient deficiencies and the leaves may turn yellow overall. The growth may be stunted as well with under-developed buds. Even if you try to compensate by providing more nutrients, there are chances of nutrient burn and the leaves turn brown and crispy. 

4. Reduced Yields

Although it seems intuitive that more light would lead to more yields, an excessive DLI can actually have detrimental effects. First, the plants can get stunted or grow at a slower rate than expected, leading to smaller plants with fewer flowering sites.

When the plants start flowering, the bud development is impeded and the flowers are less dense. Sometimes, the trichome production may be disrupted too, so the plants don't develop as many terpenes as you'd expect. 

5. Energy Wastage

Providing more light than necessary is such a waste as your plants don't grow well and you end up losing money too. Once the temperature ramps up, you'll also have to use additional cooling systems to reduce the heat, adding up to the costs. 

So, as you can see, while raising DLI levels can enhance growth to an extent, surpassing the optimal threshold may trigger issues like light stress, heat stress, and nutrient imbalances and ultimately reduce yields and bud quality. Therefore, you must monitor your plants and adjust the levels to ensure your plants are happy. 

Summary: How To Increase DLI In The Cannabis Grow Room For Better Yields?

Increasing the DLI can bring massive improvements in your cannabis plant’s yields. So, whether you are adjusting light hours, investing in bigger grow lights, or using reflective materials, each method can help optimize the light exposure your plant gets every day.

But when using these methods, be careful. Too much of anything isn’t good, and the same rule applies here. You need to carefully implement these strategies and monitor your plant’s responses. 

The key here is to find the right balance and avoid overexposure to prevent any kind of heat or light stress. With the right approach, increasing DLI can help you grow bigger cannabis plants that not only thrive but shower you with bigger buds.