Dustybowlz
Well-Known Member
1)I read the same thing. My two rooted ones are were almost solid yellow for days. After about 100ppm of nutes they greened up about 30% in about 2 days. Roots seem much bigger too. Problem is, I acutally dont have room for anything else now Everything right now is experimental.I don't think I would run nutes in the cloner after reading on the subject, what ppm are you @ in your cloner?
My 450cfm fan barely changes temps more than 2 degrees when speeds are controlled from 30% to full, how much cooler can u get ur room if you turned your fan up to max?
I have read keeping your temp probe in direct light is the incorrect way to measure temps because of radiant heat... is your temp probe in direct light?
2)Well Now that you have brought to light I have been measuring my temp incorrectly I dont know what I have been changing my AIR temp. I could try to explain my speed control settings but since I have two rooms with hoods being cooled in EACH room AND both intake AND exhaust for BOTH rooms are being run off a singe osberg 600(+?) cfm fan. Ill just say my adjustments are complicated. Right now I run the fan between 30-50% 24/0 and the temps have a 10* difference from all lights off to all lights on. It is imperitave I keep my speed control the same 24/0.
3)I didnt know I needed to control my air temp vs radiant temp. Now that I know (I remember you mentioning it before) I will switch it RIGHT NOW and start really knowing what my air temps are and how much my adjustments in speed/light height/oscilating air change my environment.
Heres a link I found to better explain what your talking about.
http://www.marijuana-ro.com/grow-faq/growroom-efficiency/how-do-i-measure-temperature-correctly.html
How do I measure temperature correctly?
You are here: Home » Grow FAQ » Growroom efficiency » How do I measure temperature correctly?
In order to know you are providing the right thermal environment for you plants through ventilation, oscillating fans etc. you need to understand the physical nature of the 'heat' in grow spaces, how it should be measured, and the mistakes that can easily be made.
Essentially there are two aspects to the thermal environment that you need to be aware of:
1. The AIR temperature
2. The RADIANT temperature
Although obviously related, these are 2 distinctly separate phenomena and your plants have different tolerances for each.
1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.
Most thermometers are only designed to measure air temperature growers often mistakenly place their thermometer in direct light; radiant energy will warm your thermometer and give a higher than actual reading.
*Assuming your air is well mixed up by oscillating fans, it doesnt really matter where you locate your thermometer. The best spot is probably about half the way up a wall, with a piece of cardboard over it (To shade it from radiant heat), exposed to the mixed air in the grow room.
2. Radiant temperature
Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.
The plants can withstand much higher radiant temperatures than they can air temperatures, but if this is too high the plants can burn.
'The hand test': Place your hand in a comfortable position for some time at the tips of your plants should be. If your hand feels hot, then the lights are too close, the radiant energy is too intense, and light burn may result. Do this test and raise your HID lights/reflectors periodically to keep light burn to a minimum.
Finally, monitor the conditions in your grow regularly as things are changing all the time, and you will soon get to understand the thermal dynamics of your particular grow space so you can get the most from it.
Editors note:
[Cannabis loves high light levels/high radiant energy levels, but exceeding their tolerance for light can result in light burn and chlorophyll leaching out of the leaves. 600's & 1000s put out a lot of light, and light burn can easily damage clones and young plants.
Light burn damage: initially the leaves look pale green (the edges may turn upwards, mimicking a Mg deficiency), then they turn yellow and finally yellow/brown as the leaves scorch.
Often you can see a circular pattern of intense light where the reflector has focused the light onto the plants. If plants outside of this intense light zone look greener and healthier, consider raising your lights.