I don't like saying things that aren't referenced so I'm going to post some "fair use" comments from fatman running them together from a thread on seedmine june 20th 2010 starting with post 310 and hopefully it will help. Coincidentally on that same thread was the first mention "ive seen" of jacks 5-12-26 for MMJ, I'd like to narrow down who used it first to give credit in upcoming publishing, so if anyone knows and can prove it please let me know for my research. What you will find even though Fatman gets banned for abrasiveness is his writings reach far into MMJ cultivation.
Fatman wrote:
Giant said: ↑
Damn, I dont know what is going on, but almost immediately after switching to the 2-1-3 ratio I started having broken branches. It must be a coincidence, but I dont know what caused it. It seems like either the buds just got 20x heavier or the branches just gave up on supporting them. They are all sagging and 3-4 have snapped clean off at the main stalk.. :(
Fatman: A higher ratio of potash typically leads to an immediatte increase in water take up. IE It is responsible for water status of stomato aperatures. It plays a major role in controlling plant transpiration and turgor. Simply put your plants put on some immediate water weight. String time!!!! Lower the humidity if you can do so without the heavy use of fans. IE a dehumidifier. If using fans a multiple of small muffins fans will lower the humidity enough so that the palnts will transpire more and therore not carry so much excess water.
Indoor mj grows are not the same as commercial green house grows where transpiration and humidity is controlled by over head misting and massive air movements. Rules that apply to commercilal green houses in the growing of products like tomatos and other highwater content plants do not transfer across to an indoor grow. Unless that grow is sadly managed at inefficient levels due to poor methodologies. mj is a high dollar crop and the growing areas are contained well enough (and most often space efficient enough) that climate controll can be better managed by dehumidifiers, CO2 supplemention and air conditioning.
It is simply a matter of upscaling your system to take advantage of all the light you provide or down garde your lighting to the lower standards of climate parameters you are willing to provide. Consider dehumification as being the replacement for natural winds/ventilation. The dehumifier and air conditioners remove humidity just like a com ntinous gentle wind. They lower the humidity anfd the plants transpire more to replace the water at the stomata lost due to the dehumification. This increases nutrient uptake. If the humidity is too high transpiration stops. DVR charts pertaining to a greenhouse grow of tomatos have no relation to an indoor mj grow. Increasing RH as showmn in the charts will cause the problem you are experiencing right now. With tomatos though it will just plump up the tomatos with lots of water.
fatman, Jun 20, 2010 Report
#310 Like Reply
skwirlgirl said: ↑
I have so many questions...I will say I'm all about lower RH and have been since I moved to THE HIGH DESERT haha. The average RH here is 22% at 7000 ft...I augment that a bit during veg (up to 50% for awhile.. but in bloom I like to drop it into the 30'
s and late I'll kill the fogger completely so it's in the 20's..Seems to tighten things up.. All done with my ultrasonic fogger. Can you give us some ideas why YOU like to run lower RH?
Fatman: There are no benefits to a high RH with a well managed and designed system. However, there are many adverse side effects to a high RH. A hig RH is only needed to protect your plants for a shortage of water and DO when your system it is unable to supply adequate amounts of water containing adequate DO to the roots. Many systems can not supply adequate water containingadequate DO for high temps. With such systems then higher RT are necessary at high temps. However high RH at high temps slows to a crawl all growth. A high RT slows or nearly stops all evapotranspiration RH amongst the plants is often 50% to 100% higher than the RT at the plants canopy (IE open areas in the grow space). Air can only hold so much water. When the air is loaded with moisture amongst the plants the stomata are not able to relaeses water, so no transpiration takes place. Yes, one can toy around with fans and ventilation and even pretend they are maintaining proper levels of RT with humidistats, misters and/or humidifiers.
The most efficient manner of getting the most transpiration is to lower the humidity down to a level just above the level whare the stomata close to conserve water. This means the plants will transpire very heavily and the growers then just removes the transpired water. This heanvy transpiration means: heavy nutrient flow, heavy uptake of DO, heavy use of CO2. All this given adequate lighting PAR means maximum growth.
In a Nutshell
Significance of Transpiration
Absorption of water
Transpiration influences the rate of absorption of water from the soil.
Water movement
By transpiration, water moves upwards and as it passes into the cell vacuoles, it makes the cells turgid. This gives form and shape to cells and plant as a whole.
Mineral salt transport
The water stream moving upwards carries dissolved minerals with it. Transpiration also helps in distributing these minerals throughout the plant.
Cooling
The evaporation of water during transpiration cools the leaves.
Protection from heat injury
Some plants like cacti, retain water by reducing transpiration. This saves the plants from high temperatures and strong sunlight.
Factors Affecting Rate of Transpiration - External factors
Temperature
Higher the temperature more is the transpiration.
Light
Light causes stomata to open and hence increase the water loss from plant.
Deficiency
Availability of soil water
When the soil gets dry, soil solution becomes more concentrated and the rate of absorption by cells decreases. This leads to reduction in transpiration and stomata close quickly to keep the water loss to minimum.
Atmospheric humidity
High humidity means high water vapour pressure outside and it results in lower rate of transpiration and as the humidity decreases rate of transpiration increases.
Wind
The wind removes water vapour and thus increases the rate of transpiration. High winds lead to stomatal closure to stop the rapid water loss and hence bring a drop in rate of transpiration. Moderate winds may also reduce transpiration by lowering the temperature of leaf.
fatman, Jun 21, 2010 Report
#312 Like Reply
skwirlgirl said: ↑
well put.
So F'Man where do you like your RH to be most of the time?...and what about the theory/practice of lowering RH late in flowering for tighter flowers?
Fatman: I run all water cooled fine droplet misted aero systems with air conditioning, dehumificication and 1500 ppm CO2 in sealed rooms. I run Honey Well Dehumidistats with a 4 to 6 degree differential. They stay set at 40%. They power window air conditioners used as dehumidifiers as they exhaust air back into the rooms not outside. I also use DIY split AC units. They seldom run and are set at 90 degrees with a 4 to 6 degree diff. The night time thermostats are set at 86 degrees. By chiller cools the light water down to 55 Degrees. I use all 250 watt lights 2 to 4 inches above the canopy. I do not chill the nutrient water (it runs about 86 to 92 degrees) as it is drain to waste. Yes it runs at a low nutrient ppm. I maintain a residual of 0.5 ppm of chlorine at all times in the nutrient water. Tap water is usaully 2 to 4 ppm of chlorine. I have found no benefit to lowering RH below 35% that is worth the risk of stopping transpiration. My buds are green leafed at harvest. I find buds that show obvious visual signs of nutrient deficiency due to long term flushing obscene.
Giant said: ↑
I am running a dehumidifier, but my RH still stays between 40 and 60% in the tent. I couldnt get it below 35% if I tried. :lol: Temps are peaking between 85 and 95*f during the days, and Im trying to work on that.. I really dont see any way to resolve that before this grow is over, so I think I am stuck dealing with it. I got as many branches as I could save tied up, and they are certainly swelling. :D
Fatman: Looks like you have hit a RH that is working well for your set up. High enough that the stomata do not close to conserve water, yet low enough to keep the plants transpiring heavily so as to still supply enough water, nutes, and DO to grow in the heat. The issue now is what is your EC. With heavy transporation you have heavy nute up take. If you have heavy water/nute uptake and strong lighting, high temps but low CO2 a high EC will cause tip burn as you have enough too much of everything except CO2. This means increased CO2 (more ventilation or CO2 supplementation) for maximum growth, or cut the EC to utilize as much of everything posible your CO2 level allows. This will cause some bud extension (thinner, longer buds) but it will still be a greater yield in a shorter growth period then would happen under low temps or higher RH. I would if the CO2 becomes an issue just increase ventilation with outside air. Supplemental CO2 is great but spendy to initially set up.
fatman, Jun 22, 2010 Report
#325 Like Reply
