View Single Post
  #10  
Old 01-31-2017, 10:13 AM
kevin24018 kevin24018 is offline
Junior Member
 
Join Date: May 2016
Location: Virginia
Posts: 11
Default

Quote:
Originally Posted by Alberta_grower View Post
If you're going to grow lettuce, the most economical methods are Deep Water Culture, or NFT. aeroponics works great too, and I'll explain how to build such a system too.

DWC is really nice because it gives you a lot of error room, especially if you're just learning to use hydroponics. With NFT and aero, a power outage or worse, pump failure, will kill your crop quick. The risk isn't as bad with lettuce compared to long life plants like strawberries and tomatoes.

You have a few options with DWC. You can build it as a raft or fixed lids, and as a constant nutrient level circulating system, or a simple add by hand system. My suggestion would be fixed lids and circulating. Unless you're growing a lot of lettuce, rafts aren't needed. The circulating and self-leveling is really nice to have, and reduces daily efforts. Here's a great link using DWC with rafts, and it's an excellent read that teaches you everything you need to know about DWC lettuce. http://www.cornellcea.com/attachment...andbook%20.pdf If you choose to go DWC, I'll gladly guide you through building a very good and low cost setup to be proud of.

The next best option is NFT. If you really like the idea of using the fence posts, and not having a water table that could leak, then NFT is your best choice. All you have to do is cut those fence posts in half, making two trays. Table saw or a sharp blade and straight edge will do the trick. Do the same with the end caps. Make some some lids from corrugated plastic with panda film glued to the tops to block light, and cut your holes square or round for your plants. I believe if you cut 1" squares, grodan makes a tapered rock wool starter that fits perfect, eliminating net cups. Put a drain at one end, and a feed tube with a mini valve connected to a header, at the other end. The slope of the trays should be between 50:1 and 30:1. You want to avoid high and low spots, so sitting them on a flat piece of melamine should prevent this.To space the slope, simply add 1cm of spacing every 30-50 centimetres; if you're using imperial 1/2" every 15-25". If you're using an 8' sheet of melamine, raise one end up 2" higher than the drain end. I believe those posts you're using are 108", so just overhand the drain end off the melamine board. For flow rate, it should be 1L/min or 1qt./ min. Simply adjust the little valve until you can fill a measuring cup one litre in a minute, and insert the tube. You can use a sturdy tote for your reservoir, and a pond pump. The support board shades your reservoir quite nicely. When setting it up, make the res accessible, and set up your plumbing so your pump can be used to drain the tank. Change nutes with the lights off or at night, so the flow isn't interrupted during photosynthesis. Ideally, it's best to have two reservoirs. Keep your res change outs as short as possible. If you're growing in batches instead of perpetual harvest, a large res can last the entire life span of the lettuce, with change outs done between crops.

For nutrients, you should have a NPK ratio of 3-2-5+micros. EC should be around 1.2 max in a more humid reasonably lit area, and reduced for higher temperatures and lower humidity. If you use the 500 scale for ppm, that's 600 ppm. pH should be around around 5.5-6.5.

If after reading all of that you're still dead set on earoponics, here's how to build a proper setup. The cost is higher for aero cause you need misters, like the ones that mist produce at grocery stores. Micro sprinklers at home depot are not a good choice, as the large droplets damage the fine root hairs. You're also going to need a higher pressure pump, and what the misters require for pressure to operate, will determine pressure. Most likely 35psi or more. I've used a sprinkler pump from home depot, and it wasn't cheap like a pond pump. You're also going to need a inline filter, just in case a small particle in your res gets sucked up. Once you've dropped your cash, start building the planter, which isn't hard. Use a rigid board, something that won't rot, and blocks light. Drill your plant sites. For a nice perpetual harvest, have the wholes increase in spacing from one end to the other. Under that top, you'll need a air gap, at least 12". Under that, you need to make a poly sealed mist containment and drain system to bring the nutes back to the reservoir. Build a manifold for your sprayers, positioning them so the mist wets the net cups, and will saturate hanging roots. Once that's all done, go and buy yourself a pump timer, or make your own if you have the electronics knowledge. 3 minutes on, 10 minutes off should suffice for most environments. In aeroponics, you run lower concentrations of nutrients, and you'll have to play with this a bit until you find the sweet spot.

In all honesty, if you're not going to do aeroponics the correct way, don't bother. I think you'll save yourself a lot of money by building the NFT system. Indoors, I don't like DWC because I'm worried hundreds of litres of water will flood my house. Outdoors, I wouldn't worry. NFT is nice because you can run a much smaller reservoir, and it's easy to keep clean. If you're concerned about pump failure, there are ways to build a back up pump circuit that kicks on when the primary fails. Can be setup with an alarm if you want to be fancy. If you're worried about power outages, theres a few options. One is to build a water tower with a lift pump, like small towns used to use. You can setup a UPC, or a solar backup too.

I'm planning on building an NFT system in my home using the same fence posts you want to use. If I get around to it, I'll also make the files available for a restrictive flow meter you can 3D print if you have the technology. It will allow water to be pumped at any reasonable rate, and it will deliver 1L/min using a hole as a flow limiter, and any excess flow goes back to the reservoir. It's pretty awesome, cause you don't need to set the flow with tiny valves for every tray, and it's impossible to screw up.
wow thanks a lot, I think dwc is the way to go after reading all of that, I've been doing a ton of reading, have some books etc, guess I'll do some more, thanks again.
Reply With Quote