Medpot Minstrel: Hydroponics Medical Marijuana

Thursday, April 05, 2007

Watering intervals in my ebb & flow system

Three things are necessary for figuring out how often to flood your flood and drain (ebb and flow) system. First, a good quality digital timer; second, previous growing experience; third, common sense.

When you’re growing from seed under a transparent plastic humidity cover, you only water your rockwool cubes every 12 hours, twice a day. When your seedlings get bigger, you’ll notice that they drink more, so you switch to four times a day, but you lose the humidity cover since you want to avoid fungal infestations.

When you transplant your seedlings into your ebb & flow setup under an HID light, it is advisable to start your regimen at three flood and drain cycles per day, usually during the 18 hours when the light is on. So you’re flooding every six hours.

When you switch to the 12-hours light, 12-hours of darkness for the blooming stage of your plants, they’ll probably be tall enough to be watered four times during a 24-hour period. Usually 3 times at four hour intervals during “daylight,” and once during the six hour midpoint of your 12-hours of “night.”

I arrived at these watering times through trial and error. I used to have a cheap timer which left me no choice, I had to flood my system for 30 minutes. With a digital timer you can set the duration of the flood stage. I find that a 20- minute flooding makes more sense and is better appreciated by my ladies. Their roots don’t like to be deprived of oxygen for too long.

Speaking of what my ladies appreciate, they have visibly perked up with the introduction of Advanced Nutrients Connoisseur into their reservoir. It’s as if after being fed an adequate but humble diet, all of a sudden you were given a five-star gourmet meal!

This is week 4 of my ladies’ bloom cycle, so the EC of my nutrient solution is 2.28 and the parts per million is 1600. I’m doing a medium-feeding regimen—don’t want to overdo it! I can always do a heavy feeding the next time around.

In addition to 186.5 mL of both Connoisseur A and Connoisseur B, I’m also feeding my ladies 115.2 mL each of Mother Earth Super Tea Bloom, and Grandma Enggy’s Humic Acid and Fulvic Acid.

The Super Tea provides that organic touch that benefits all cannabis plants. Continuing in the same vein, the calcified organic substance known as “leonardite” is the source of both Humic Acid and Fulvic Acid. These products turn my hydroponic reservoir into a rich, black, humus-like growing medium.

576 mL of SensiZym is also added to the mix in order to supply over 80 different types of enzymes that are living organisms. They love to munch on plant debris in my clay pebbles, turning this debris into absorbable nutrients for my marijuana plants.

34.58 grams of Big Bud Powder went into my pre-mix tank the night before, along with 11.52 mL of Barricade, and 345.6 mL of B-52 vitamins. Big Bud is a powerful bloom booster that I’ve used before to maximize the size and potency of my buds.

Barricade is a potassium silicate product that strengthens cell walls and thus wards off numerous pathogens and pests, that are unable to penetrate and have to go elsewhere to find food.

Once I mix all these ingredients in my pre-mix tank, I take a pH reading every 30 minutes, until my pH becomes stable. If it’s not 5.6 I add pH Up and or pH Down until it does read 5.6. Advanced Nutrients Medical recommends 5.6 pH for hydro, and 6.3 pH for soil.

How often you flood your ebb and flow system has to do with the strain of cannabis that you’re growing. Trial and error is recommended. Start with three floodings during the light period.

See if your grow medium and the root mats sticking out the bottom of your buckets are totally dry when your lights turn on. If the mat is totally dry, you probably need to insert a flooding during the hours of darkness.

Remember, over-watering is just as harmful and under-watering. Mark the inside wall of your reservoir to see how much your ladies drink during a 24-hour period. Also, some water will disappear through evaporation.

It’s a good idea to top up your reservoir each day with fresh water. Take a pH reading every time you top up. You might need to readjust your acid-alkaline balance. Also, be aware of how you EC and ppm readings change as a result of these toppings up.

Never flood more than 50% to 75% of your grow medium. Your roots have to breathe, even during the flood cycle. The absorbency of your grow medium is also a major factor in how often you have to flood your system.

If you’re using rockwool, for instance, which soaks up and retains a lot of water for an extended period of time, you’ll have to flood less often. Coco coir only absorbs 60% of its weight in water, 40% always contains air so it allows your roots to breathe.

Clay pebbles are highly porous so they also retain a lot of oxygen, especially when the nutrient solution drains and air rushes in to replace the liquid.

Watch your plants before and after the waterings and you’ll be able to tell whether you are watering too much or too little. If you notice that the leaves of your plants are slightly curling up, that is a sign that they are desperately trying to retain moisture and you should definitely water more often.

Any sign of wilting before watering means water more often. If your plants wilt after watering, then your are flooding your system too often, so cut back. Allow the medium to dry out between waterings.

You don’t want to have your roots immersed in the nutrient solution for too long, because you risk drowning your delicate roots. Sometimes, even 30 minutes is too much, but definitely never keep your roots submerged for longer than an hour.

Cutting off their roots’ oxygen supply can have disastrous results on your plants. In fact, the tech guys at Advanced Nutrients Medical recommend airstones in all hydro set-ups, even the ebb and flow kind that I have.

Airstones can be purchased in any aquarium shop and they help oxygenate your nutrient solution to keep your roots supplied with O2, even when they’re sucking up the life giving liquid that you’re feeding them.

And when that solution contains Connoisseur, it’s like feeding your cannabis plants a diet of liquid filet mignon.

posted by Wes @ 5:12 PM


At 1:42 AM, Blogger Debra said...

This article is JUST what I was looking for. Very informative. Thank you very much. I'm just setting up my ebb n flow and you provided exactly what I was looking for, albeit, it was on pg 5 of my Google search . Please keep up the great woek.


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