Small Fish, Big Pond

The basic idea of using hydroponics instead of a pot of soil you can maximize the growing potential of a small space. It’s a myth that growing with hydroponics is better than soil; it’s more accurate that hydroponics grow as well as the perfect soil culture, and often in a smaller area or with denser plantings. You MAY get just as much from 20 pots on your balcony, but why not be sure you get the best growth and save a little floor space in the process?

The drawback is that it’s not as simple as pouring dirt in a pot, adding a plant and watering daily. A hydroponic system needs a bit of forethought and planning. Luckily it’s easier than it first looks, and using commonly available components for your local hardware store it’s not as expensive as one might think.

I really wanted this to fit the typical urban living space so the idea I came up with was a long narrow growing area; 8ft long, and about 1 foot wide. Since most apartments have another apartment overhead there would be a place to dangle supporting wires to clip the growing plants to as they got bigger. That way you wouldn’t have to worry about wind knocking the plants over or the narrow hydroponic trays having to support the plants. I also decided that by splitting the system into two halves you can adjust the footprint from 8×1ft, to 4×2ft and have some flexibility in the configuration (like bending it around a corner, 4ft per side).

Last year I tested out the basic idea, seeing if an NFT setup would even work outside in a non-greenhouse setting. It worked and was spectacular, outperforming the regular soil garden many times over. The main lessons I learned is that external plant support is a must, plants “drink” more water out in the heat, and even though soil-borne pests are eliminated it can be harder to manage pests that can climb easily (no slugs or snails but earwigs were awful).

So this year I’m making the “production” model of the 8×1ft hydroponic garden. I’m going to try tracking resource usage a bit closer; I tracked electricity usage last year but water was just estimated. Electricity usage was quite minor (only $30 for all summer), less than leaving a porch light on at night. Water usage was MUCH less than a traditional garden. In fact Lifehacker linked how to make a window garden; the comment “…let’s mother nature take care of the feeding and watering.” really caught my eye. Obviously these people don’t live in the western US, if you want fruit bearing plants you have to add massive amounts of water here. Which isn’t good because we’re already technically a desert, we’re told to conserve all that water so it can go downstream to California so they can grow produce there, or to Las Vegas to be used in the Belagio fountains.

Hydroponics simply means using water to add nutrients rather than soil, there are many different methods to actually carry that out. However with size being an issue the best solution in my eyes was the “Nutrient Film Technique”. DIY guides has some excellent articles on this and other hydroponic methods.

The way NFT hydroponics works is by running a small amount of nutrient solution over the roots, allowing oxygen to still reach the roots rather than complete immersion.

Contrary to what many believe the roots of a plant also need to breathe just as much as the leaves. In fact the more moist air around the roots the better. Some hydroponic systems completely immerse plant roots in water but use air bubblers to introduce oxygen to the nutrient solution so the roots don’t suffocate. Aeroponics takes this to the extreme by spraying the nutrient solution into the air as a mist to maximize the roots ability to absorb water, nutrients, and oxygen.

Our NFT method will run nutrient over the roots for 15 minutes, then shut off for 15; a more ideal ratio would be 5 minutes on, 10 minutes off, but getting a more specialize timer costs more (maybe later). The idea is that fresh nutrient is sprayed on the roots then given a chance to be absorbed along with oxygen from the air. The risk is that if the roots dry up the plant dies. The closed nature of our setup will allow some lag time if the power goes out, or a sprayer gets clogged but be aware that on a hot day if you lose power for 12 hours you may lose plants if you don’t water them. You’ll also want to check the plants once a day, if there is improper filtering and debris clogs a sprayer you’ll notice the plant looking wilted.

The cool thing about NFT hydroponics is that it’s very easy to scale up the size and capacity of your system. Many commercial hydroponics users make use of this to create huge deployments with the same basic equipment we’ll be using.

Also the system is a closed system, in that virtually nothing gets in or out including light, keeping things as dark as possible reduces algae buildup in the system. Properly sealed there will be little to no evaporation of water, and very little water or debris will get in (but some always does). So everything is used by the plants, if there is excess it runs back into the system and is used again. Again this means that you do have to keep an eye on things. It’s amazing how much water plants will drink up and evaporate off their leaves on a hot day.

I found that topping of the water supply needed to be done about 3 times every 2 weeks on average. On hot weeks water needed to be added about every 3 days. Nutrient are only absorbed as needed so as water levels fall the nutrient solution gets more concentrated, but so long as more water is added it should never be too much of a problem.

About every 2-3 weeks it’s good to dump the nutrient solution and mix up some more. Since nutrient solution is just a very diluted fertilizer (and most the nutrient is absorbed by the plants when you change it) you can dump in any growing soil area, it will just help the plants there. Use it to water your potted plants, pour it out on the grass, in your soil garden, or in flower planters by your door. Avoid dumping it directly in the water supply down a drain; even though the fertilizer in it is negligible the ocean doesn’t need any help with all the crop runoff there already is.

Building the system

Last year’s test was a bit unwieldy. With apartment dwellers in mind I want this one to be small and manageable. I started by getting a8 foot long 4” diameter vinyl fencepost from the local home and garden shop. Then cut it in half.

I just used a simple hacksaw and it was done in about 3 minutes. I marked straight lines but the bit at the top wasn’t perfectly straight, nor does it need to be. When the caps finally go on we’ll put plumbers putty on the seam and it will fill any imperfections.

Some quick work with a file to get rid of the burrs.

Now it’s time to mark where the planting stations will go. I used the complex method of scribbling on the back of an envelope to plan the positions. As an experiment I’m putting 4 plants on one section and 5 on the other. They start 4” from the end of the tube, and stop 7” short of the hole drilled for access to the drain. The hole for the drain is 3” from the other end of the tube. This is to give enough distance from the last plant so that it’s roots won’t clog up the drain. As you can see in this shot of last year’s system the root systems will fill up the tube quite alot.

Once you know the correct distances between holes mark them along a measuring tape along the length of the tube. Then mark the center point horizontally for each position. Measure twice, cut once.

To drill the hole I just used a 3” hole drill bit from the hardware store. However using it with a handheld drill is a bit tricky. Make sure the fence post is properly secured and you have a very firm grip on the drill. Start slow. After the sawtooth part of the hole saw has started into the post you can speed up the drill. Don’t apply much pressure, just let the teeth slowly cut their way in. Once the first few teeth cut all the way through the drill will try to wrench itself out of your hand so be VERY CAUTIOUS!!!!

It’s better to damage and replace the post or the drill than to slice, gouge, or destroy part of your body.
If this seems a bit out of hand for you don’t be afraid to give up and have a professional with a drill press do it for you.

All sites drilled. On the far right are the drain access holes. Notice the spacing to fit 5 planters on one and 4 on the other.

Here’s the netpot in the hole after drilling and de-burring with a file.

Clearance is pretty good.

Just like the planting locations the holes for the feeder lines need to be positioned correctly so they will spray into the planters. So figure out where the holes in the feeder lines will be then drill corresponding holes in the vinyl tube a couple inches down so they don’t overlap.

The hole in the feeder will be two inches to the right of the dot marking the mounting hole in the vinyl so it will spray onto the rear of the netpot, drip down, and flow to the drain (to the left in thie shot).

The hole is as wide as the zip tie but smaller than the head of the zip tie, so it goes in the hole, around the feeder line, back out the same hole, then through the head of the zip tie. This way you can pull it tight and not worry about drilling two holes.

Finished mounting the feeder lines. This tube has two feeder lines as an experiment but last year worked fine with one. The higher line on the right will spray onto the netpot to keep it wet. The lower line on the right is positioned to spray directly onto the roots “upstream” of the netpots.

And what the feeder lines look like on the inside.

Final setup and working system in part 2.