I will be growing in coco with a recirculating drip system. Most coco grows are drain to waste, which seems like a waste of nutes to me. I know recirculating coco is possible there are a few growers who do it. But there is very little information on how to do it.
The argument is that if it is dialed in drain to waste coco will use less nutrients than a recirculating system. I am just not buying that. So although drip systems are fairly common in coco coir grows, most systems do not recirculate nutrients.
But I believe it can be done. The key is to carefully monitor the nutrient levels in the reservoir. The other key is to treat coco like what it really is – a hydroponic medium. Most growers treat coco like it was soil, which it definitely is not.
Growers often wait for it to dry out before watering again but in reality coco will perform best if nutrients are continually flowing through it.
To that end I think a 50/50 coco perlite mix would be ideal for a recirculating coco drip system. When nutrients don’t continually flow through coco salt build up occurs. There are many forum posts that say Drip Clean at 1 ml a gallon will stop salt build up in coco. But I am not sure that will be necessary.
Growing In Coco Is Hydroponics
It is important to understand a few things about coco fiber because it has some unique properties. Most hydroponic medium like perlite or hydroton has no or extremely low CEC (cation exchange capacity) For more detailed info on CEC there is an article here.
Basically, CEC refers to a soil’s ability to hold onto essential nutrients and provide a buffer against soil acidification. The higher the CEC, the more nutrients it can hold so a clay or silt based soil can hold much more than a sandy soil for example.
This is important if you’re growing coco because it has a fairly high CEC for a hydroponic medium. So coco tends to build up high levels of potassium and it also will hold on to calcium and magnesium. That is why coco nutrients will have lower K values than regular nutrients and cal/mag supplementation is often necessary. A very good article on coco hydroponics can be found here.
The problem is figuring what is in your reservoir. You may test at 800 ppm but the question is 800 ppm of what. Well chances are there is significantly less calcium, magnesium and potassium than what was in the original mix. And that is why recirculating coco systems can be difficult to manage and are usually avoided. Still, I am going to give this a try.
First I should say I am using Canna Coco bricks. Some bricks are poor quality and high in salt too. But Canna bricks come out just like the stuff in the bag. They are low salt and precharged. I tested mine and they were at about 400 ppm and pH 6.2. I then flushed out all nutrients from the coco so I could start with a clean slate. I probably didn’t need to do this but again, 400 ppm of what?
My coco was mixed 50/50 with coarse perlite to improve drainage and prevent over watering. I think the large amount of perlite will limit the amount of nutrients that get stored and allow me to run a pretty much continuous drip without any drainage problems.
Building My Recirculating Coco Drip System
Since this is a test run for my next Biker Kush grow I did not want to reinvent the wheel. I wanted to test some Heavy 16 and Aptus products and that was not practical in my aeroponic system.
However I was easily able to convert my aeroponic totes over to a recirculating coco system. I simply removed the misting heads and lined the totes with mosquito netting to keep the coco medium in place.
You can see my previous Biker Kush grow hanging to dry. The lights were only on a short time while I set things up.
Here are my totes. I am using my complete aeroponic set up minus the misting heads. System is running. The water in bottom is because my res is filled higher than drain holes right now. Mosquito netting being put in. I used a 6 x 12 foot piece that cost $7 at a local fabric shop.I pulled it up and flattened it out by wrapping it around my fittings.Totes were filled with a 50/50 coco perlite mix. I used a coarse grade perlite with larger chunks. All settled in and filled. It is about 9 inches deep. Here are my Biker Kush clones waiting to be planted. These Biker girls are home and tucked into their new beds nicely.Here is the Biker Kush 3 days later and just about doubled in size. I guess they like their new home.
I am running a 1 minute on and 10 minute off cycle right now 24 hours a day. Everything is moist but not wet or soggy. These ladies are under 720 watts right now 24 hours a day. In about a week they will get topped and switched to 12/12 to start flowering.
My Aquatec 8800 is rated at 5 gallons per minute wide open, but I doubt it is putting out much more than half that because of the fittings. Still adjusting things, and when the plants get larger I may need to change the cycle but for now all is good.
My reservoir was filled with 5 gallons to keep it below the drain holes. The totes may hold a gallon in reserve because they never drain totally. I added a 900 ppm nutrient mix of CaliMagic and Heavy 16 flower and the next day it was down to 500 ppm which is pretty close to what I flushed out of the coco.
I have topped up the res with more full strength nutes and brought it up to 600 ppm. Then added Cal/Mag until I hit 900 again. It was down to 700 the next morning. I know that between the coco and the fact OG Kush is a cal/mag whore that I will be adding it back quite often. I plan on replacing the res about every 2 weeks like a regular hydro grow.
I now have full documentation for growing in coco with a recirculating drip system in my new Biker Kush grow since these plants were flipped.