vapor pressure deficit

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vapor pressure deficit

Post by EasilySuede » Tue 10th Oct 2017 08:35 pm

...or VPD
understanding the relationship between temp and humidity, and their combined
effect on plants, will really help your healthy-grow-environment kung fu...

simply, when the humidity is low, keep temps low-
the dry air will "wick" moisture from the plant without
the need of a high plant metabolism (temp influenced).
when humidity is high, bump up the temps to increase
the plants metabolism to work past the increased air
vapor resistance, and less wicking assistance.

once i started monitoring the flower room's humidity
with a decent device, and adjusting the temp based on
that, everything greened up nicely within a week,
and minimal crispy leaves at harvest.

all below from ... e-deficit/

For cannabis, there is a sweet spot that varies through the growth cycle of the plant. Look at the plant and compare what we are trying to do with what a body builder does. We are trying to stack weight on while maintaining a beautiful structure.

By adjusting the sweet spot of your room, you can also speed or slow the uptake of nutrients to the plant. Using these little tweaks, you will optimize the environment for your plants to thrive in.

Typically in weeks one and two, the plants are drinking less as they fully enter the flower cycle. Their root mass is still growing, and they are on their way to maturation. In this stage, the VPD should be around 8.0-11 which is a temperature of 77° – 79°F and 65 – 75 percent humidity.

Once the plants are in flowering and need to uptake more nutrients, the VPD should be around 10-13.5. This would be weeks three through four. To achieve this, temps would be a bit lower around 75° – 77°F with a humidity around 55 – 65 percent.

As you move through the flower stage, the VPD would then follow to between 13-15.5 in weeks five through nine. This would mean lower temps around 74° – 76°F and a relative humidity between 42 – 51 percent. This cooler and drier condition will allow the medium to dry out more evenly so that you could have more consistency with irrigation dry downs. The cooler temps will also better preserve the terpenes on the plant.

In this cycle, you will also adjust your feeding accordingly, boosting the amount and times you feed as you run through the flower cycle. As the VPD goes up, so to does the pressure on the plants to pull water in through the roots. You will see your buds fatten up through the flower, and as you increase the watering cycle, also increase your EC. By increasing the amount of nutrients you are giving your plants at the right time in the flower cycle, you will see your yields dramatically increase.

more info... ... ferential/ ... ltivation/ ... cit/2/1519

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