We have been growing root crops and everything else in our wicking beds with great success. We would like to discuss designs of beds and their operation in this discussion.
Our beds have been based on 12 inches of growing medium and 12 inches of rock reservoir. We have been using aquaponic system water to fertilize the beds. We have been growing primarily carrots but have had some volunteers such as chard sprout and they all grow extremely well! How are your beds set up????
Just to clarify the beds in the foreground or lower terrace are wicking beds. The bed in the back are trickle trough cinder beds. There is about 2 weeks between plantings in the wicking beds. The large plant in the back is kava that is a year old.
The black Rubbermaid container in the last pic is filled with 12 inches of cinder. There is a piece of weed mat on top of the cinder. Just below the weed mat is a horizontal perforated pipe drain that exits the tub at 11 3/4 inches. On top of the weed mat is the growing medium(recycled coir). The stand pipe is used to fill the cinder reservoir and check the water level. The pipe is perforated below the weed mat. The half barrels work on the same principle but have 6 to 8 inches of cinder reservoir at the bottom. I am experimenting with designs on the barrels so each is a little different.
The way they work is we fill the cinder reservoir with system water until it overflows the drain below the weed mat. The reservoir level can never get so full that it water-logs the media. The natural wicking capacity of the rock and media draws up the moisture to the roots of the plants. When the reservoir has water the media stays moist. The media sometimes looks dry on the surface but is moist just below. I have found that the media stays very cool on hot days even though we are using dark containers. When the plants are small I have to top off the reservoir every other week. As the plants mature we have to top off weekly.
We intend to integrate the barrels into the system so we never have to top off the reservoir.
Oh I almost forgot to mention that we also fertilize the beds with the poo from the solids settling tank. When we do this we top water direct on the coir so the poo stays there and does not go anaerobic in the rocks. There are worms in the coir which work their magic with the poo.
Yes it will work without a settling tank and system water only. I put my solids into the wicking beds to use it for growing veggies instead of giving it to my fruit trees. A wicking bed that is not tied into the system can be fertilized with whatever you desire.
Chris, your design was featured in one of Tim's newsletters a few months ago, and its been in the back of my mind ever since. I was thinking of plumbing the wicking bed system to my green tilapia growout tank by connecting the feed line to the rock water reservoir under the growing media and capturing the overflow to a sump tank for return to the fish tank. This would keep the water reservoir at a constantly full level. This may not be desirable as the growing media may need to periodically dry out for optimal root growth. But I was planning to test this out anyway. The moisture content of the growing media could possibly be controlled by varying its depth to compensate for the constantly full water reservoir below.
Another design option could be to put a timer on a pump to feed the rock media to control the growing media dry out time. In this case, a return sump tank may not be necessary because the volume of return water may be insignificant. The overflow can simply be diverted to water ground based plants (Side note: Bill, as you know, fish water has poo in it, and should work as media fertilizer. My worms love it, and my ground based plants love it). This would also act as a periodic water change for my green tank as I would have to top it off it with clean water.
I dunno, as with anything, the proof is in the pudding, and Chris, you're making pudding. I still need to test it out. Thanks again for sharing.
Larry, thanks for the reminder about poo in system water. These wicking bed designs seem to offer plants the ability to develop the dual root zones that Vlad Jovanovic discussed on one of these forums recently - very interesting!
Your system sounds a lot like a enlarged Earthbox Growing system. http://www.earthbox.com/
You might be able to go on to the site above and get water level sensors for your barrels.
I have been using a similar system, using half whisky barrels for years. The only difference is,
I just used tap water for moisture.
I inverted the cut-off bottom of a rope-handled bin in the bottom of the whiskey/wine barrel.
I drilled a hole in the center of my inverted pan to allow for a water tube. Instead of recovering the
water, I drilled a hole in the side of the whiskey/wine barrel at the level of the top of the inverted
pan. When I watered, usually every 3 days, I let the water run until it ran out of the side drain hole.
I filled the barrel with grow medium and planted usually tomatoes and other plants. A half whiskey/wine
barrel would last about 8 to 10 years.
I can see where using the used vermicasting soil would be a great advantage. I could have used
the same system using fish water and recovering it back through a filter to the fish tank.
Here is the advantage of your cinder. It performs the filter function for you without having to resort
to a seperate filter bed.
Do you grow your fish in a dark enough environment to allow the nitrites to be changed to nitrates
in the fish tank or do you allow this to happen in the settling tank?