This is a gold mine of cannabis growing laboratory research

[purpledomgoddes]

from the British Columbia Ministry of Agriculture and Lands:

Floriculture Production Guide: 2008

Guide to best management practices in British Columbia for ornamental crops, including potted foliage and flowering plants, bedding plants, and cut foliage and flowers

Appendix C. Light Measurement Conversions

PDM, what do you think about this next part, from Chapter 3, Managing the Plant Environment:
Quote:
Plant height is influenced by the difference (DIF) between day and night temperature. A positive DIF (higher day than night) will produce taller plants. A negative DIF (higher night than day) will produce shorter plants. Plant height can be decreased by lowering the day temperature and also by increasing the night temperature. It can also be decreased by introducing a relatively cooler temperature, or DIP for two hours starting just before sunrise. DIP and DIF affect the length of the stem internodes rather than the number of leaves.

more excellent finds ljb. have been attempting to detail the effects of diff and temp and vpd manipulation since beginning posting here. good to see more members digging out and implementing the science.

the 'lag' period, or pre-dawn period, when stomata closed and water uptake @ minimum, is when most influence upon plant can be effectuated.

have basically described the above method(s) in several posts here. good to know other gardeners on a mission to master their plants+environments!

exceptional work ljb. keep enjoying your garden & increasing the knowledge base!

 

[JackTheGrower]

a 1k mh, or hps, ~1 foot away from the plant will provide ~5,000 lumens, which is ~50,000 lux, which will be ~150-250 par watts; due to spectral deficiencies.

the sun is ~450 par watts of full spectrum light.

required ~20 photons to make/store 1 molecule of sugar.

get the 1k's 2"-6" away and will get close to achieving leaf saturation, or ~300 par watts. in general, get lights as close as possible to plants, as long as air circulation is optimal, they can handle being very close to lamp. if cannot get/mimic full spectrum of sun, saturate plant w/ light by close proximity.

It's hard to make it practical in a small space but thankfully I'm vindicated on moving past the 50 watts per sq ft I read about years ago.



In the last grow, I had this result in the center under the 1k hps. This strain never grew this way before I grew them right up under the 1k hps. Also this strain is a cross of two common medical strains bred by Berkeley coop to elevate mood so it isn't one of the newer strains from a seed company. It was crossed by me in 2001 and was grown from those seeds in 2005-2006 with the cool air of winter.

I changed to cool tubes this season and added two 250 MH's for "Side light" since that is where the buds didn't look like the above.

So thanks for the post in that I know I am not up to the optimum but I'm closer.. Will try and keep the light close, as it can be raised about 18 inches as the tops grow on the plants.
However as seedlings we don't need to be close to cause tight inter node spacing. They do really well with it at a distance.
One thing to note is the light energy, just from this setup, warrants protective eye ware.




FYI


Jack

 

[Haps]

OK, there should be a prize for reading this thread stoned. What I got out of this is, you can run 1Ks very close, as long as you cool. They can take the light, not the heat.

 

[LJB]

...

 

[Chief]

This is a gold mine. Its nice to see studies with numbers. Well worthy of a bump

 

[BORNaSMOKER]

i want the fukll text... anyone have access to these journals for free??

 

[BORNaSMOKER]

full pdf here

http://www.zshare.net/download/7789950149a4d199/

 

[boroboro]

Thanks for finding the paper, BornaSmoker. Nice to see something useful come out of that US Govermnent grow program in Mississippi.

 

[BORNaSMOKER]

Thanks for finding the paper, BornaSmoker. Nice to see something useful come out of that US Govermnent grow program in Mississippi.

nice to be able to give something back now and again! realised i can get anmy journal... until my girl's uni course finishes!! proper handy though

 

[LEPgrow]

So using 2 lep from gavita and 600w gavita pro turned down 50% in a 5x5.
Figuring 400 ppm co2 what would be propper umol levels ? 800 for veg and 1200 for flower? In flower ill bump up the 600w to hundred perfent over transition week. If I tell gavita what range I want they will tell me where to put lights. Anyone have good numbers?

 

[Phaeton]

The study I used to set up my garden was older and the only difference was the max hourly intensity a leaf could use came out to 1600 umol instead of 1500. Otherwise the results were almost identical. This makes sense as plants pretty much grow one way. From the results in my own testing room I find the lower number more appropriate.

A 400 watt CMH will give 1500 umol at about eight inches, depending on reflector type and material.
The bulb puts out too much heat at this distance and the light falloff towards the lower leaves stresses the plant.

LED intensity depends on beam angle and density of diodes.
A 400 watt Black Dog puts out 1500 umol at about eight inches without the heat and the light is more focused than bulbs with reflectors.
Advanced XTE 400 achieves 1500 umol at twelve inches and the lower leaves receive dramatically more light due to the smaller footprint used.

Using a combo of CMH and LED keeps the lights in my garden about 14 inches back at 1100 umol.

24 hour tests show a full day's average maximum to be closer to 1100 umol for 16 hours. The 1500 umol hourly maximum can be kept going only about ten hours before the plant is full and needs to process the energy.
LED's need only 850 umol due to the greatly reduced green and yellow output. The reds and blues are more efficient and the plant needs less.
The plants energy processing ability changes as it matures. A plant three weeks from harvest can only use half the light of a newly transitioned plant.

The rooms run 83 degrees. This leaves a safety zone. As the room cools plants slow their growth. As the room becomes too hot the growth stops.
When the weather is stormy I set the temp down to 80 to lessen any wind effects on the intakes.

That study and a couple others on how spectrum use changes with intensity improved my crop by an average of 15% over using 75 degrees with the light warm on the back of my hand.

The closer to the limit the tighter the tolerances must be.
Tools used are:
red meter in milliwatts (mw)
blue meter in mw
UVB meter in microwatts (uw)
Quantum Flux meter (PAR meter) in umol
Temperature and humidity
Setting up a room requires all the above meters to be used. Then they go back on the shelf until a new light is purchased.

Thumbnails show clear day readings taken at solstice in Fairbanks, 65 degrees north.
A 24 hour recording sensor is used to track and save night temps as well as day temps.

Research articles like this one make a difference whether the garden is large or small.

 

[LEPgrow]

So 1000 umol/m2/s would be a nice 12/12 intensity for peak flower?

 

[LEPgrow]

Phaeton where you using co2?