What is DLI
Daily Light Integral (DLI) is the total number of photosynthetically active radiation (PAR) photons (traditionally those between 400-700 nm and now 400-750nm) incident on an area over the course of a day.
DLI is a function of both the intensity and duration of the photosynthetic light falling on the target over a day and is most commonly expressed as moles of light per square meter per day or mol•m−2•d−1
Importance of DLI
Specific plants and other photosynthetic organisms, like corals, require different daily light integral levels to achieve optimum growth. There are many resources available that list different DLI recommendations.
Different strains have different DLI stress points, and while the range is wide, virtually all strains can handle somewhere between 40-50 DLI.
If your light cannot metabolize the current light, you will experience light stress because if an absorbed photon does not get absorbed, it creates heat in the plant and that heat can cause stress.
While a plant can only grow as fast as the weakest link, the primary driver of plant metabolism is light. Careful testing and logging will allow you to optimize your DLI targets.
If light-stress is seen below 45 DLI, the grower should investigate ways to improve their nutrient throughput, environmental conditions and so on - to be able match the metabolism demanded, or dial the DLI target back.
Cannabis recommended flowering 20-65 DLI - will have a uniform increase in yield proportional to DLI right up to 45 DLI, with many strains going as high as 50 DLI or more. For vegetative stage the DLI should not be less than 25% of the flowering DLI to avoid potential "light" shock.
Recommended DLI Measurements
To make an accurate measurement of the DLI during a day with changing light levels, a high-quality quantum sensor must be used and coupled with a data recorder to log and sum all the measurements from the day. A quantum sensor, also known as a PAR or PPFD (photosynthetic photon flux density) sensor, measures the intensity of photosynthetic light incident on a target.
We recommend the DLI & Photoperiod Display Sensor. The sensor automatically calculates your DLI and displays the reading on the digital display. You can also download all the data to your computer.