Air Circulation

Actions:
-Water
-Changed clone tray water

VEG
Water
pH 5.8
~15 gal

HPS Veg isn't wilting as it usually would in square pots, except with the trees that weren't trimmed and cloned from, which leads me to believe that less moisture is absorbed from the roots following a heavy trimming. This would also lend more credence to the idea that trimming any foliage will actually result in a decrease in the overall metabolic processes of the plant. Trimming, therefore, must be timed precisely to allow for adequate recovery times, especially during pre-flowering.

MH Veg is progressing better than I had initially hoped. Branches are noticeable thicker, with even growth all around and consistent vertical growth, albeit a little slower than HPS. There was a possibility that MH, at 750 watts, was actually a major bottleneck in my production, but so far this theory has been dispelled by the progress of these plants. There is a fair degree of certainty that the bottleneck was attributed to pot size, as that is the only major difference between HPS and MH at this point. PW Lights and small square pots would initially show promise, but would stagnate while still under MH, producing skinnier branches, along with less desirable clones. Coupled with reckless and mistimed trimming in veg and bloom, root-bound pots would be a major reason as to why yields have been consistently low.

MIDDLE
Water
pH 5.9
~19 gal

Steady calyx development into colas. Vertical growth has nearly halted completely throughout the room. Most branches still haven't reached second level trellis. GG without SCROG, although boosted, seems to have shown the most vertical growth, as expected. I'll have to compare the yield of this individual tree with the Abusive in the back left corner to determine if SCROG produced any positive results; this Abusive was similar to GG in width, although GG had to be boosted to match in height.

Considering how the GG has developed, it would probably be better with future rotations to contain height below the first trellis upon transplanting into bloom without SCROG. All other variables considered, SCROG could actually hurt yields. In the past, when yields were higher without the use of trellis', branches were allowed to stretch horizontally, allowing for light penetration to the lower half of the canopy. Healthy development in bottom to mid colas was actually a benefit to achieving higher yields. For now I can only observe the differences in yields between the Middle and Master, but I intend to use the trellis in the Master as more of a support structure rather than a growth regulator.

MASTER
Water
pH 6.0
~15 gal

Bubba has ripened faster than all the other strains, which may warrant an early harvest. One GG in particular, however, hasn't developed at the same rate as all the other trees, and may actually need to be harvested earlier than it should for the sake of sticking to the schedule for the entire room. Hopefully this tree ripens fast enough over this coming weekend to meet quality standards. Abusive looks like it's deteriorating as well, and probably needs to be cut down early.

This room is a disaster. Powdery mildew, inconsistent growth, and the overall derelict appearance of the plants are all going to contribute to a shitty harvest. I'll have to spray fungicide again, and aggressively so, which might hurt the quality even further. I'll also be considering harvesting using a hydrogen peroxide bath to wash as much mildew off as possible. I'll also be flushing this room for the rest of the rotation.

Air Circulation
Proper air circulation involves using fans with adequate CFM ratings relative to the volume of the grow area to displace stagnant, warm, or humid air and replace it with fresh air. It was conceived that displacing hot air and pulling cooler air was necessary simply for temperature control, but the reasons behind it are actually biological.

The stomata on the leaves function as a way for the plant to absorb CO2 and oxygen while dispersing water vapor as a waste product in a process called transpiration, at which point the plant will draw more water from the roots. The stomata will behave according to the conditions of the plant and its surroundings. With a bright light and enough moisture available through the roots, the stomata will become dilated, allowing for more CO2 and oxygen to be absorbed. As the soil becomes dry, the stomata will close to preserve water, thereby halting photosynthesis. With too much water (overwatering) the stomata will dilate to release as much water vapor as possible, but at a rate that is dangerous to the plant's survival and development.

As the stomata releases water vapor as a waste product, this waste must be displaced from the room via dehumidifiers and inline fans. If the air becomes too thick with water vapor released from the stomata, the plant will have less access to essential CO2 and oxygen, which will disrupt photosynthesis depending on the stage of the grow. This is generally offset through the use of dehumidifiers and inline fans.

Oscillating fans present an interesting challenge. Placing these fans too close to the plants will cause "wind burns," where leaves become damaged through constant air being blown onto them. Oscillating fans would ideally be placed to gently circulate air around and above and canopy to keep the air from becoming stagnant.

Calculating the amount of CFM needed involves basic math. The Middle room will serve as an example here:

Volume: 10' x 10' x 12' = 1200 cubic feet

Adequate extraction time is about 3 minutes:

1200/3 = 400 CFM

Given a standard 6" inline fan provides 400 CFM, one should be adequate for a room of this size, but there are also other variables to consider. The number of lights, active/passive intake, use of carbon filters, and CO2 enrichment are all factors that should be included in determining a final CFM requirement, although a general rule of thumb is to always provide more CFM than required regardless of the situation.

In the case of the Master, with a requirement of 750 CFM, two 400 CFM exhaust fans with an active intake should be able to adequately circulate the air. The only foreseeable problem would be humidity, which can easily be offset with proper placement of oscillating fans and dehumidifiers.