We decided this year to try some hydroponic lettuce in the greenhouse to go along with the new expanded tomato operation. This particular hydroponic system is called an NFT system, which stands for nutrient film technique, it uses a recirculating nutrient solution that is washed over the root system in shallow trough. We got this system thru Cropking Inc. who supplied the greenhouse system, it comes with some basic construction plans and all the parts needed to setup the table and recirculation pump system.
Construction the NFT system.
The first thing we needed to do was locate all the parts for the system, Cropking bundled all the parts together to make this alot easier. Let get to constructing!
The kit comes with several lengths of galvanized pipe, some of the ends are swaged so they fit into other pieces to make the required 26 foot sections for the width of the table. The longer top rails are then connected to the shorter cross bracing and legs forming a solid base. The sections of pipe are held together with clamps that bolt together around the pipes.
Next the drain line is plumbed together and secured to the back end of the table, you should have some fall from the front to the back of the table due to the legs being cut shorter toward the back, this is all taken care of at the factory, I had to make some minor tweaks due to the slope of the greenhouse slab. You should also have some fall to the solution reservoir from left to right.
The 4 inch pipe comes already drilled with the holes that will line up with the channels, and are standard 10 ft sections.
The nft channels look like gutter material that you would put on your house except they are only about 1 inch deep, they are made of pvc and open on the ends, end caps and plumbing are included.
The channels above have already had end caps glued on(you have to do this yourself) and the 45 Degree elbows glued on as well, the the elbows connect into the hole in the drain pipe. At this point the channels just need the covers put on and this end is mostly done, they will still need the irrigation tubes connected but that part goes with the plumbing.
Next up is the nutrient reservoir and pump, this is the heart of the system, this type of hydroponics involves mixing a solution of nutrients and circulating it over the roots of the plant, the solution is computer controlled to keep the nutrient levels correct (more on this system later).
The pump is plumbed to feed the fertroller sensors and the on to the front of the tables where the tubing connects the each individual channel to feed the plants.
There is a 100 micron filter in between the pump and the channels to keep large debris out of the tubing, the the pipe tees off into two feeding zones.
In this photo you can see the feeder tubes and the cap for the channels, these have pre-cut holes where the plants will be placed after they have sprouted.
after all this has been put together the next item is the fertroller, it is the brain of the system, controlling the PH and nutrient solution, it also reads the water temp. The set up on this is fairly easy since the folks at cropking have it all wired up and mostly preset.
After this is setup and all the drains are returned to the reservoir we set up the nutrients and get the whole thing running within the supplied parameters for a day or so, and there you have it an NFT lettuce system
Next time I’ll show you how the lettuce is looking! Stay tuned