The Importance of Maintaining Proper Rez Temp

Discussion in 'Aeroponics' started by Peflora, Jun 26, 2015.

  1. Been growing hydro with outboard rez for 4+ years, pretty much non-stop


    Summer heat here begins around late June, but this year it was already hitting 90*s in late May


    My room has no attic/insulation, so it gets > 90*s without running the ac, which adds ~ $100/mo to my bill


    While I cooled the room I never paid attention to rez temps. DUMB DUMB DUMB


    When I started this exercise to passively cool my rez I didn't have a thermometer, but could tell by feel that it as > 80*s, and that ain't good!


    Using a combination of a 24 can Igloo cooler + 10 feet of 1/4" copper coil (Lowes/HD) + one gallon jugs of frozen water I soon got temps down to low 70s, where they remain during lights on: over-nite they can/do rise to mid 70s by morning. I replaced the ice water with blue ice, which lowers the temps to the high 60s


    The pistils have responded over the improved temps by becoming more plentiful, fatter and fluffier: the buds bigger.


    But, according to Ed Rosenthals Marijuana Growers Handbook (page 186) there is more to the story in that there is a relationship between ambient temps and rez temps. And while the information is geared more toward warming a cold room, the roots are more important than the ambient temps


    "Ideally, the root temps should be (70*F/20*C)


    If the ambient temp is > 75*s (my problem ~ 7 months of the year) the water should be no more than 70*s; over 90*s rez temp should be ~ 65*s


    I included a pre and post pic, although the first is ~ 30 days earlier in bud, I think you can see how bud development was severely affected


     

    Attached Files:

    • 001.JPG
      001.JPG
      File size:
      1.3 MB
      Views:
      67
    • 001.JPG
      001.JPG
      File size:
      1.6 MB
      Views:
      65
  2. Another observation: the amount of trics from the first grow to the reveg is easily +200% already. I thought this strain was just low in trics, though still mighty potent. Clearly not the case, or, and this is a possibility, I switched from another LED panel which did not have as much ~ 3000-4000 nms, a spectral rang that sats love


    Gonna be fun to compare the results

     
  3. My friend runs his a bit warm he just uses dutch masters zone to kill the nasties..second pic does look way better nice job
     
  4. I tried Zone last grow. Almost killed one of my plants. Be VERY careful


    Band-Aids can have bad consequences


     
  5. Hes been running it 3yrs and gets a lb every 2 weeks so idk hes not complaining
     
  6. Here is a real good article:


    .
    \t\t\t\t\t\t\t\t\t\t\t\t\t<div class="layoutArea">\t\t\t\t\t<div class="column">\t\t\t\t\t\t\t\t\t\t\t\tNutrient Temperature - Oxygen and Pythium in Hydroponicsby Dr. Lynette Morgan, Courtesy of NA Greenhouse
    \t\t\t\t\t\tThe hydroponic nutrient solution is not just a mix of fertilizer salts and water, there are a number of organisms and compoundscommonly found in our hydroponic systems that we need to be aware of. One of the most important of these is dissolved oxygen,which is vital for the health and strength of the root system as well as being necessary for nutrient uptake.
    \t\t\t\t\t\tMost growers are familiar with the need to have some form of aeration in their nutrient solution - whether they be in a recirculationor a media based system. In NFT systems, this is often accomplished with the use of an air pump or by allowing the nutrient to fallback into the reservoir, thus introducing oxygen. However, the effect of temperature of the solution on the dissolved oxygen levelsand on root respiration rates also needs to be taken into account. As the temperature of your nutrient solution increases, the abilityof that solution to 'hold' dissolved oxygen decreases. For example, the oxygen content of a fully aerated solution at 10C (50 F) isabout 13ppm, but as the solution warms up to 20 C (68 F) the ability of the liquid to 'hold' oxygen drops to 9 - 10ppm, by the timethe solution has reached 30 C (86 F), then it's only 7ppm.
    \t\t\t\t\t\tWhile this may not seem like a huge drop in the amount of dissolved oxygen, we have to remember that as the temperature of theroot system warms, the rate of respiration of the root tissue also increases and more oxygen is required by the plant. For example,the respiration rate of the roots will double for each 10C rise in temperature up to 30C (86 F). So the situation can developwhere the solution temperature increases from 20 - 30 C (68 - 86 F) during the day, with a mature crop and a large rootsystem, then the requirement for oxygen will double while the oxygen carrying capacity of the solution will drop by over 25%. Thismeans that the dissolved oxygen in solution will be much more rapidly depleted and the plants can suffer from oxygen starvationfor a period of time.
    \t\t\t\t\t\tThe symptoms of oxygen starvation which can occur in both NFT and media based systems can be difficult to pick up as they arevery general signs. Media based plants are just as prone to oxygen starvation in hydroponic systems as those grown in solutionculture, but here we must also take into account the 'air filled porosity' of the media used. This is simply how much air canpermeate between the particles in the substrate and selection of a free draining media which won't break down will ensure thatmaximum aeration is going to reach the root zone. Injury from low (or no) oxygen in the root zone can take several forms andthese will differ in severity between species. Often the first sign of inadequate oxygen supply to the roots is wilting of the plantduring the warmest part of the day when temperature and light levels are highest. Insufficient oxygen reduces the permeability ofroots to water and there will be the accumulation of toxins, thus both water and minerals cannot be absorbed in sufficientquantities to support plant growth particularly under stress conditions. This wilting is accompanied by slower rates ofphotosynthesis and carbohydrate transfer, so that over time, plant growth is reduced and yields will be affected. If oxygenstarvation continues, mineral deficiencies will begin to show, roots will die back and plants will become stunted. Under continuinganaerobic conditions, plants produce a stress hormone - ethylene which accumulates in the roots and causes collapse of the rootcells. Once root deteriorization caused by anaerobic conditions has begun, opportunist pathogens such as Pythium can easilytake hold and rapidly destroy the plant.
    \t\t\t\t\t\tAnother more visible and longer term effect of oxygen starvation which also occurs in waterlogged crops is leaf 'epinasty'. Epinastyis a downward curvature of the plant leaves, resulting in plants which look wilted. If the oxygen starvation continues and is severe,then eventually leaf chlorosis yellowing, premature leaf and flower abscission will occur.
    \t\t\t\t\t\tThere are a number of things we can do to make sure our nutrient solution is carrying sufficient dissolved oxygen, and this isimportant when we consider that many of the root diseases encountered in hydroponics have occurred because the root systemwas damaged in some way, with anaerobic conditions being a major factor in many situations. The first most important factor toremember with oxygen is that the best way to introduce this gas into the nutrient is to have the solution fall back into the reservoir,and the greater the drop height, the better the aeration effect. Breaking the flow up into a fine shower also assists by introducingmore air bubbles into the tank. Secondly, while nutrient EC does reduce the oxygen carrying capacity of the solution, the effect isvery small and temperature has a much greater influence on oxygenation. Reducing excessive solution temperatures will ensuremore oxygen can be held by the solution and the rate of respiration by the roots will be kept down to optimal levels. Thirdly, factorssuch as nutrient flow rate, channel width, length and slope have a large effect on oxygen levels- faster flow rates, greater slopesand shorter channel lengths all assist with prevention of oxygen starvation.
    \t\t\t\t\t\tPerhaps one of the most common problems in hydroponic systems is the Pythium pathogen and what many growers don't realizeis that Pythium being an 'opportunist' fungi, often takes advantage of plants which have been stressed by a combination of hightemperatures and oxygen starvation in the root zone. Pythium is usually described as a 'secondary infection' meaning that thePythium spores which are actually common in just about all hydroponic systems, don't actually attack the plant until it has beendamaged in some way. Even very clean hydroponic systems and grow rooms which are isolated from the outdoor environment willhave some Pythium present as these fungal spores are naturally present everywhere on a world wide scale - in the water, soil,vegetation, carried in the air and in dust, so it's difficult to eliminate the source of this disease. However, one way we can reducethe 'spore load' is to sterilize any water supply which may be contaminated with high levels of Pythium --- water from dams, andstreams should always be sterilized before use for this reason if Pythium is a problem.
    \t\t\t\t\t\tUnder the right environmental conditions, virtually every plant species is vulnerable to Pythium, which not only causes 'dampingoff' of seedlings but causes root and stem rot of older plants. Symptoms of Pythium on older plants are a wet rot, root systems willbe browned, roots hollow and collapsed. Plants may appear to grow poorly and wilt for no apparent reason --- indicating that anexamination of the root system when called for. Pythium has an optimum temperature range for infection of plants, which isgenerally between 20 - 30 C (68 - 86 F), although infection can occur outside this range when damaged plant tissue isavailable for rapid colonization by the pathogen. Low concentrations of Pythium that may not cause problems at lowertemperatures will be disastrous at higher temperatures, particularly where the warmer conditions are associated with a lack ofoxygen in the root zone and plant stress.
    \t\t\t\t\t\tThe best preventative measure against Pythium attack is a healthy, rapidly growing plant as this is an opportunist pathogen andwill enter at the site of tissue injury or if the plants are overly succulent, weakened or stressed for some reason. Often rootdamage during the seedling stage as plants are introduced to the hydroponic system is a danger time for Pythium infection.Pythium is of greatest threat during the seed germination and seedling development stage when plants are most vulnerable toattack, and adequate control and elimination of the pathogen during this stage is the best preventative measure of Pythium controlin hydroponic systems. Strong healthy plants will develop resistance to Pythium attack during the seedling stage and this willprevent problems at a later stage of growth.
    \t\t\t\t\t\tOther preventative measures include the use of a well drained media, thorough disinfection of all equipment between crops (astrong hypochlorite solution --- bleach is the most effective), and control of pathogens during the seedling stages with a suitablefungicide, long before they are introducing into your hydroponic system. Occasionally a very high spore load, combined withexcessive temperature will result in Pythium attacking even healthy plants, if this is the case, it is likely that there is an activesource of spore production present and the system must be shut down and disinfected. Some growers have found the use ofwetting agents and chlorination of the nutrient solution beneficial in limiting the damage caused by Pythium, however extreme careneeds to be taken when using products such as calcium hypochlorite as to much active chlorine will kill sensitive plants. UV light,hydrogen peroxide and ozone have also been used to kill Pythium spores in the solution, however these can have major effects onsome of the nutrient elements in solution and careful consideration should be given before using these methods. Sterilization ofthe water supply with these methods, before nutrient are added however, is effective at reducing or eliminating Pythium from theoriginal water supply.
    \t\t\t\t\t\tTherefore by ensuring your plants are healthy and stress free, you will not only get the highest growth rates possible, but also
    \t\t\t\t\t
    \t\t\t\t
    \t\t\t</div>\t\t</div>\t\t\t\t\t\t\t\t\t<div class="layoutArea">\t\t\t\t\t<div class="column">\t\t\t\t\t\tprevent problems such as Pythium infection occurring. The variables to remember with regard to the nutrient solution is thataeration is vital to maintain the dissolved oxygen levels, temperatures should be keep within an optimum range and Pythium isalways present, but a healthy plant is the best measure of protection against a disease outbreak. About the oxygen requirement ofplants when in flower...its not always the case that plants require more oxygen because they are in flower, a plants oxygenrequirement is linked to the size of the root system, temperature and nutrient uptake rates, rather than the presence of flowering.Since plants such as tomatoes tend to have a rapidly developing root system at the time of flowering, it's important to maintainadequate oxygen levels. With tomatoes, the requirement of oxygen in the root zone increases gradually up until the time ofmaximum fruit load and rapid fruit expansion, where the high rates of nutrient uptake increase the oxygen requirement quitedramatically. On the other hand, if oxygen is deficient during flowering, then the flowers and subsequent fruit may drop off as aresult, or they may be undersized and may fail to pollinate.
    \t\t\t\t\t\tDr Lynette Morgan is the Director of Research at SUNTEC International Hydroponic Consultants, based in Manawatu, NewZealand.
    \t\t\t\t\t\tHydroponics University
    \t\t\t\t\t\t\t\t\t\t\t
    \t\t\t\t
    \t\t\t</div>\t\t</div>Hydro-U is a service of Simply Hydroponics and Organics On-line as part of our consumer education program. We welcome yourfeedback. Your input is what makes this site work. Please contact us with any questions or ideas.
     
  7. Excellent contribution!


    Especially the importance of drainage of the medium, which is why I no longer use RW. I tried hydroton, but it was just too messy


    The Dollar store sells bags of polished river rock which is; fast draining, keeps roots temps cool, easily removed from the root ball after harvest, easy to clean and disinfect, AND, can be reused for decades


    Comes in sizes. I use the smallest for early veg

     
  8. How cold is to cold for the rez temp?
     
  9. I would think not lower than 62*s<span style="background-color: rgb(255, 255, 255);"></span>
     
  10. Same for DWC? I should have been clearer.
     
  11. #11 jollyrancher1, Jul 1, 2015
    Last edited by a moderator: Jul 1, 2015
    If you read the article, the author took the temp all the way down to 50F.
    I know of a grower who takes it to 58F for the last two weeks.
    If I go lower then 63F I will get water pooling from condensation(dew point) dripping from the plumbing.
    IMO you will hit the dew point before you go past the lowest temperature the plant will tolerate.
    If you can, take it to under 60F and watch the growth.
    It is scary it is so fast.
    Here is a picture of what my plant did when my chiller thermocouple (temp controller) went bonkers and the temp went into the low 50's.
     

    Attached Files:

    • Like Like x 1
  12. Interesting. Seems logical to make the root temp as well as tent temp even cooler for the last couple weeks


    I don't get what your plant pic is about though

     
  13. #13 jollyrancher1, Jul 1, 2015
    Last edited by a moderator: Jul 1, 2015
    If you look at the pic, you can see the accelerated growth that happened when the temperature decreased.


    The stalk almost doubled in diameter.
     
  14. Not without seeing a 'before' picture
     
    • Like Like x 1
  15. Oh c'mon.


    You can see how the growth accelerated at the base vs the growth an inch above.
    Notice how it expanded as the temperature decreased?


     

Share This Page