flow rates and hydro cycles for drip irrigation

How to grow indoor marijuana, Hydroponic marijuana growing systems. Grow lights, Rockwool systems, DWC, NFT, Aeroponics, Organic etc

I'm a first time grower planning a pretty ambitious SoG project (80 sqaure feet). I'm an engineer by trade, and in order to design efficient drip irrigation systems I need to know some numbers.

First, is there any merit to doing a continuous, low flowrate drip instead of a periodic drip schedule? If so, what flowrate (gph) should I use per plant?

Second, is there any merit to having drip cycles during the night hours of the day?

The vegetative room will be on 18/6 days. I was thinking about doing four, 15-minute drip cycles, one every four hours during the daylight, on hours 0, 4, 8, and 12. There will be two independent drip systems (two reserviors, two pumps), but both pumps will be on the same timer. One system feeds the mothers and clones (0-4 weeks) on 1/2-strength nutrients under eight 4-foot T5 HO flourescents. The other feeds the main vegetative plants (4-8 weeks) on full-strength nutrients under 1000W MH.

The plants for these systems will be in one of two media. Young clones (<2 weeks) will be spray-watered manually once per day. Older clones (2-4 weeks) with be in 4" rockwool on a drip tray. I was thinking of using one 1-gph inline pressure-compensating dripper per plant at this stage. This equals 1 quart of solution per plant per feeding, or 1 gallon per day. Is that on the right track?

The mother plants and main vegetative plants (4-8 weeks) will be in 3.5-gallon buckets of clay pebbles with a 1/2" drain in the bottom. I was thinking of using four 1-gph inline pressure-compenstating drippers per plant (arranged neatly around the stem) at this stage, for a gallon of solution per feeding and four gallons per day. Is this too much?

The flowering room is of course 12/12. I was thinking three, 15-minute feed cycles during the daylight at hours 0, 4, and 8. There are two crops of 6 plants running simultaneously in the flowing room, 4 weeks apart, each under its own 1000W HPS. Full-strength nutrients in a single large reservior. The plants are still in 3.5 gallon buckets with clay pebbles, and I'm thinking four 1-gph drippers per plant again. This means 1 gallon per feeding and 3 gallons per day. About right?

I know it's kind of hard to overwater when your dripping through pebbles into a 1/2" drain, but I want some degree of efficiency. Also, I read somewhere that the rule of thumb for reservior size is that it should hold enough solution to run through one day's feeding cycles. This means I need two 24-gallon reserviors in the veg room and one 36-gallon reservior for the flowering room.

Thanks for your help. I'm glad that there's so many resources for first-time growers like me. I'm sure that your experience and my general toolishness will yield great results! Of course I will photodocument my progress here once I begin construction (May 1).

One more question: How do I know when my first seedlings are large enough to be cloned for sexing?

I know the resulting clones should be 8+ inches tall before sexing, and that plants should be around 20-25+ inches for flowering. I would guess that there's a number of inches somewhere between 8 and 20 where I can start cloning. Or is it a matter of node count?


as far as cloning...check this post out

"What Do You Want From Me?" -Pink Floyd

I am 35% addicted to Porn. What about you?

manic wrote:as far as cloning...check this post out


Yes, that's a good guide to cloning. This one is a little bit more thorough [http://greenmanspage.com/guides/hydroponics.html]:

Cuttings are to be selected from healthy parent stock only take a cutting from non-woody stems if possible take at least 25mm or 1 inch more than required immerse the cutting in water make a cut with a sterile razor or scateurs whilst underwater just below a branch By cutting underwater you eliminate air bubbles forming at the incision and blocking the rooting process. make this cut diagonally (about 45 degrees) to the stem (still underwater) cut off the branch just above the first cut to provide another surface for roots to strike (still underwater) Gently scrape the stem for 25mm above the cut to disrupt the cells on the stem (still underwater).

Use the sip of life technique for hard to propagate cuttings by using an extremely sharp razor blade to puncture the stem about 25mm from the base of the cutting. This puts a small amount of water into the stem and must be a very thin cut, as the incision must close itself up when you withdraw the blade. The cutting will now suffer less dehydration whilst rooting.(still underwater) remove the cutting from the water (Optional) dip cutting in a root rot treatment to avoid stem rot during rooting dip the cutting in a rooting hormone, preferably a Gel, or a Liquid and stir around for 15 seconds. Powders can rub off. Place in Perlite and Vermiculite Mix or a Rockwool cube, and keep the medium moist. Dehydration is the major cause of cutting failure because there are no roots to replace lost moisture. Best strikes above 20 degrees Celsius. Up to 30 degrees Celsius.

Mist the cuttings with water to stop dehydration (and a vitamin B solution such as Superthrive if available) Using an aquarium as a mini-greenhouse keeps dehydration down to a minimum. Small clear Propagation shells are available with vents designed for this purpose at Hydroponic Stores.

A Cutting will usually live or die within the first 3 days (72 hours) Use up to 24 hours of low light intensity (such as Fluorescent light) to ensure photosynthesis is still occurring, but not so bright as to cause dehydration. After the cuttings appear to be rooting, vent the propagator to avoid stem rot or root rot from the high humidity. Remove the propagator after 1 week if all is well. When in doubt, ventilate the mini-greenhouse but use warmth and keep some humidity in the propagator for as long as you require to confirm they have survived.

But that doesn't say anything about how big the mother must be for cloning to succeed. I found this later [http://www.a1b2c3.com/drugs/mj012.htm]:

If your mother plant is from seed, it should be at least 1 foot tall. But if you need lots of clones, let it get big. It pays to have patience sometimes. I can always find the room for a bigger plant.

I guess the best subjective indication is that you must have a branch of the main stem that is 4-6 inches in length.

There are sooo many cloning techniques described on the web that it's difficult to know what's worthwhile and what's not. Some guides recommend a 1/4-strength "bloom" nutrient solution to be sprayed on the plants, some soak the rockwool in a solution with formulex and/or superthrive. Some swear that rockwool is junk for cloning and use perlite/vermiculite. There's also the stuff that coats the leaves and retains moisture vs. a using a hood.

It seems that after decades of hydroponic marijuana growing, there would be a more-or-less accepted best-practices for cloning/rooting. I'm temped to believe the people who claim success with simple methods, like the guide you linked above. I think that if you combine careful cutting methods (i.e. the completely submerged method I quoted above) with daily misting of the leaves and hood and re-wetting of the rockwool... then you'll have good success.

I'm planning my SoG procedures around a 75% success rate for cloning. Is this reasonable?

you type alot lol
"What Do You Want From Me?" -Pink Floyd

I am 35% addicted to Porn. What about you?

OK I'll be short: 1/4 gal every 4 hours or 1 gal per day for young vegetative (4" rockwool), 1 gal / 4 hours or 4 gal / day for old vegetative, 1 gal / 4 hours or 3 gal / day for flowering (both 3.5 gal clay pebbles).

Is this about how much I should plan on feeding?

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