PAR DLI

[Jimi O'Connor]

So I just got a light meter. Long story short according to the meter, my light wasn't on a high enough power setting. It was at 40% power. When using the meter it's suggesting I should turn it to 80% power. I'm wondering if that's to big a jump and will hurt the plant.

The plants in the 2nd week of flower

The DLI is around 20 and the PAR was around 600.

That's if I follow the meter and increase the power to 70 % or 80%.

70% still is a little low on some spots of the plant. 80% seems to check most all of the boxes.

I guess my question is if I increase the power from 4 to 8 is that going to mess up the plant?

 

[twentyeight.threefive]

So I just got a light meter. Long story short according to the meter, my light wasn't on a high enough power setting. It was at 40% power. When using the meter it's suggesting I should turn it to 80% power. I'm wondering if that's to big a jump and will hurt the plant.

The plants in the 2nd week of flower

The DLI is around 20 and the PAR was around 600.

That's if I follow the meter and increase the power to 70 % or 80%.

70% still is a little low on some spots of the plant. 80% seems to check most all of the boxes.

I guess my question is if I increase the power from 4 to 8 is that going to mess up the plant?

Doubling the light output instantly is going to stress the plant. I'd suggest slowly increasing the light output. Like one setting a week or something like that.

 

[Delps8]

Congrats on buying a light meter and putting it to good use. I've littered the pages of RIU and other sites urging growers to take that step because it's the easiest way to get healthy plants and high quality crops.

DLI of 20 mol is very low but there's no reason to not increase DLI very rapidly. Bruce Bugbee addressed this issue, specifically, in YouTube interview that he did with Dr. GrowIt, if I recall correctly. The question posed used that particular value - 600µmol. The answer was simple and unequivocal - take it to 800µmol and see how the plants react. If they don't show signs of too much light (tacoing or rotating leaves around the petiole so as to reduce the area exposed to light), then raise them again the next day.

There's no magic to this but the key point is not if cannabis can handle the increased light level (I routinely grow my autos at 80 DLI and my photos at >1100µmol) but how well grow environment + your plants are able to handle the new light levels. Some strains can only tolerate 800 under the best of conditions but I have seen two grows where plants can't tolerate > 500µmol. The reason for both of those grows was that the growers hadn't watered their plants correctly and the soil was hygrophobic. Assuming that your grow is in good shape, there's no reason why you should be able to feed your plants at the 1k level.

If you go from 600 to 800 and don't see any negative reaction, I would next jump to 900µmol. That's right in the middle of what the 800-1000 range which is generally used to describe the light saturation point.

Once you bump to 900, check to see how your plants react and, if everything looks good, go to 1k. Assuming that your plants react positively, there's simply no reason to not give them that level of light.

Again, you should be able to jump 200µmol the first day and then another hundred or two in the next day. Cannabis thrives on high light and it's absolutely clear that crop quality and quality (the ratio of the mass of flower to above ground mass) increase as light levels increase.