Aeroponic Greenhouse

After a friend gave me a tutorial on hydroponic gardening, I just had to experiment myself. I setup my [formerly] soil greenhouse with a hydroponics system to grow pepper plants. 




Two years ago, I built a greenhouse with a 8' x 8' footprint in my backyard. The first year I setup the growing bed with thrity gallon-sized pots. Each pot had an individual irrigation line that went to it and the whole system was fed water from a timer attached to my house water supply. I don't have any photos of that first year with plants in it, only after the summer when everything had been chopped. All plants were grown in a soil medium. My beef with this system was that the plants didn't have enough canopy space or root space. I decided that the next year I would use less plants.

Last year, I gutted what I had, lowered the bed and installed a lining of sorts in it. I setup eight 3-gallon pots with peppers and tomatoes (same as previous year) and filled the bed with expanded clay aggregate where there were no pots. The purpose of the clay pellets was to take up volume because I was going to be flooding the bed and didn't want to have to use an excessive amount of water just to feed the plants. This system worked to a certain extent but I could see that I wanted more oxygen to my roots.

This year I decided to completely redo the irrigation system again and I opted for trying my hand at aeroponics - growing with no medium. In an aeroponic system, the plants roots are suspended in the air and are misted with sprayers of some kind. I also decided to rip off the poly on the structure and cover it with an inexpensive corrugated plastic material. The idea with this new covering was to reduce hotspots (more diffusion) and add robustness to the structure (poly gets really fucked up by heavy winds and UV). I'll write more about this year's system in future updates.



This year's system

So as I mentioned in the previous update: this year I decided to go with aeroponics. The system I designed and built is meant to need only small amounts of human intervention. All the feeding is done by a 1200GPH MagDrive Pump submersed in the main reservoir (80L).

The main circulation route : Water is added to the reservoir by turning on the pressure at the faucet on the side of the house which is connected to a hose that travels through an underground conduit and pokes through the lid of the reservoir. I manually add a predetermined volume of each of a 3 part hydroponic nutrient solution. I say predetermined to mean that I had figured out how many milliliters to add of each solution based on the duration of the growing cycle and the volume of the reservoir. I had all the values in a table posted in the greenhouse.

After the nutrients are added the system can be turned on and the pump propels the solution through tubing up through the reservoir lid and into the rootzone. The solution becomes pressurized in the 1/2" PVC tubing in the rootzone and makes the microsprinklers spin, misting the entire area underneath the corrugated plastic sheet. The mist condenses on all the surfaces in the rootzone and collects in the bottom of the basin and a drain routes it back to the reservoir.

I started the plants on June 5th this year. I wanted to make sure they didn't have to endure any cold nights.



Summer Progresses

As the plants started to grow into their new home they showed only minimal growth until the roots touched the bottom of the basin, around the end of June. After this point the growth was much faster and new shoots would start their way skyward almost daily.

As you can see from the photos. There wasn't tons of growth in the first month. Some of the plants grew faster than others too. The chili almost grew the fastest but it didn't grow as strong as the jalapeno or banana.

The bottom photo to the right shows the roots of the Jalapeno plant after being in the system for just over a month. These plants were all started from 2" pots. The root cubes were placed directly into the netpots when the system was started. Although not being a totally sterile way of doing things, it sure was simple. I had the filter to get rid of the dirt in the system so it didn't clog the sprinklers anyway.

You can see so far that this system is of a good design and is working exactly as intended. I really didn't have any surprises .... besides the surprise of how big the plants got and the sheer number of fruit they produced. Which you'll see in the next updates.



Good looking plants!

It's October now, but I thought I would finish off posting all the pics to this project as I have them all archived on my machine anyway.

The greenhouse worked great. That's really my sentiment when it's all said and done. I learned a lot from it, I got lots of fruit which I've shared with friends and family and burned a few mouths in the process. ; )

I actually ran the system on straight water for the last 2 months of operation (Aug & Sept). The plants survived fine. I even noted a bit of growth during their water only period. It's part of my experiment to see how much micronutrients plants really do require.

Next year I think I might tear down this structure and build a geodesic dome greenhouse in it's place. More usable growing area plus better sun penetration plus more interesting design.

Some of the things I didn't like with this design :

1. No support for plants, a makeshift guy-wire had to be improvised to keep the plants from toppling over.

2. Reservoir too small. Even though it was in fact 80 liters of water, more is better. I would have liked to have an automatic refilling float valve even. Couldn't be that hard to rig up.

3. Not enough light reaching plants. That 'clear' plastic sheeting I used probably only admitted 60-70% of visible light. A better type of glazing would have been better. I'm investigating the idea of pillows of two layers of plastic with argon in the air space between them as a glazing substitute. Good insulation, excellent light transmission.

It would be sweet to have a year-round greenhouse prototype happening next year. The pillows and the geodesic structure might be the key. I wouldn't be able to grow hot peppers year round but maybe Tomatoes. We'll just have to see.



The product

I thought I might as well include a photo of the peppers I pulled out of there. Keep in mind that I also pulled many off while it was growing to sample them as they ripened. This is just what was left on the 4 plants when I unplugged the system in early October.