The relationship between increasing DLI and yield is almost linear. In his videos of earlier this year, Mitch Westmoreland shared some of the info about the research that he's done as a PhD candidate under Bruce Bugbee. One nugget that he provided was that cannabis yield can be estimated as 0.2 to 0.3 gm of flower for each mol of light that the plant has received over its lifetime.
I measure PPFD pretty much every day and sample one point for seedling but up to 20± points when a large plant is in flower so I could add up the number of mols and estimate my yield. But I don't and I won't because…
Because all PPFD/DLI tells me is how much light has fallen on my plant. What matters is how much light my plants can use.
That's a blinding flash of the obvious from someone who spent $600 on an Apogee three years ago.
Again, the number on the meter isn't an end in itself. Instead, it's a means to an end.
The goal is to get as much light on your plants as they can handle. If you're only able to get 600µmol on your grow, that tells you that you've got a problem with your grow because your plants should be able to handle at least 800µmol. But unless you're stuck at those levels, the number isn't very important.
The goal though is to get as much light on your plants as they can handle because light is the only way plants can make food and because, all other tings being equal and as long as the plant is able to use the light you're giving it, a plant getting more light will result in a larger crop and a higher quality crop.
