I just posted this over in Amy's thread, but why should she get to have all the fun! Let me start by thanking
@FelipeBlu for bringing DLI (Daily Light Integral) to my attention to begin with!
Here is a general definition:
Daily Light Integral (DLI) ...calculates the entire light provided to a plant per day. The farmer can choose DLI as a reference in light daily intakes given to his culture. DLI is expressed in moles per square meter per day.
An enclosed space with a LED lighting system with low PPF may emit the same DLI than that of a horticultural LED with a strong PPF if it extends its photoperiod. The DLI is very useful to determine the overall growth of your plants.
Here is a DLI calculator (you will need to be able to determine your PPFD, which can be done with a lux meter and online calculators if your light is fixed spectrum...hard to do with blurple/mixed spectrum lights without an actual PPFD meter).
Then there is this chart as it relates to cannabis:
Figure 1. Recommended light schedule for cannabis across propagation, vegetative and flower stages of growth.
There is a good article on the page where that came from
here. This is an excerpt:
A SHORT DAY, HIGH DLI PLANT
Since cannabis is a highly versatile crop valued for its flowers, maximizing floral biomass and understanding the photoperiod thresholds (see Figure 1) for cannabis has been my primary focus over the last few months. This is because cannabis takes on more light than any other flowering plant I have worked with in the past. And the cultivation of the plant is just the beginning of the crop’s productization as dried flower, extract or oil which requires a thorough understanding of plant maturation and the necessary treatments just prior to harvest.
The most noteworthy aspect of how cannabis differs from typical greenhouse plants is how the plant thrives under high-intensity light. Cannabis is one of the few plants which flourish under more than 950 to 1,200 photosynthetic photon flux density (PPFD) in full bloom, i.e., 41 to 51 daily light integral (DLI). However, several factors in a controlled, sole-source lighting environment need to be optimized to transition a cannabis plant to this level of high intensity lighting — we call this transition process “photoacclimation.” During the early stages of growth — propagation and vegetative growth — cannabis plants can require some of the DLI levels the plant will experience during its life cycle, but with the long, 18-hour photoperiod, the DLI is relatively easy to achieve at low light levels.
After this vegetative bulking period, the reduction to 12-hour photoperiods during the reproductive growth stage can confuse the need to still maintain relatively high DLI levels during this stage of growth. While DLI requirements dip to a degree, the loss of the six additional hours of light should not be dismissed; growers who do not account for this change will see poor yields in terms of flowering productivity. This is why high-intensity PPFD lighting is especially important during the bloom stage. Some growers assume the same supplemental or primary lighting can be used for every stage of growth. Th is has led to bad experiences with some LED systems, which were not designed to
provide enough photons to promote efficient photosynthesis during a short
photoperiod.
Cannabis can be photoacclimated at such a pace that you can reach extremely high levels of PPFD near the tail-end of the bloom growth stage (see Figure 1). Even then, it is critical to administer this level of high-intensity light in short, 12-hour cycles to ensure the plant receives full and uninterrupted cycles of darkness to properly develop its reproductive organs, e.g., flowers for cannabis. These light intensity levels will ensure the plant hits the proper DLI, so it will produce yields to its fullest potential, which is one of the most important factors many new growers underestimate when first taking on a new cannabis strain.
Keep in mind that the DLI generally goes up during the period of flowering, but needs to be squeezed into only 12 hours (as mentioned in the third paragraph above). This is why you need to bump your lux during flowering!
If you grow indoors, you have all the info you need
. Now let's figure out what the sun is providing for those of us outdoor growers. If you are in the US, you can use this link:
Funding the Future of Floriculture
endowment.org
Let's see how I can apply this information to my grow. We are in September, and so here is a map from the above link that shows what the DLI is for California in September:
As you can see, the DLI for coastal CA is 40-45 DLI. And when we look at the chart above, we can also see that 45 is the peak DLI for cannabis. So I'm perfect, yes? Well, no. Because I'm guessing this map assumes I get direct sun from dawn to dusk, and I don't.
To calculate my
actual DLI, I could measure my lux and plug that number along the number of hours/day I get that lux into the DLI calculator above. I'm not going to go to that trouble right now because I have nothing growing. But I could, and so could you.
for stopping by!
