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A friend of mine, Ingrid, started growing her own lettuce mix at home using a non-circulating hydroponics system.  I was very interested in what she was doing because it requires no electricity and only a one time nutrient feed.  She sent me brief, but great, instructions and I did a little research on the Kratky method of hydroponics and decided to share what I've done.

These instructions are brought to you after six months of successful growing.  Ingrid had been growing for a year by the time I gave it a try.

I've also attached a PDF file of one of Dr. Kratky's papers outlining his method and how it works... if you want to get all "sciency." 
 
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Step 1: What you'll need

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Underbed box 41 QT/39 L (approx 35" X 17" X 6") and/or 5 gallon bucket (I will be using both in these instructions)
Drill
Utility knife
Tape measure
Plastic paint primer and paint
1/2 inch x 1/2 inch elbow (optional)
Rubber grommet 3/4 inch OD x 7/16 inch ID (optional)
Clear vinyl tubing 1/2 inch OD x 3/8 inch ID (optional)
1/2 inch drill bit (optional)
2 inch hole saw
8 - 2 inch net cups per lettuce bed.
Perlite
Strap to hold shape of container once it's filled with water
PH water testing kit
Hydroponic nutrient (your choice of brand)
Lettuce seeds
Place to set up your lettuce beds

This setup should come in at under $30

Step 2: Where to grow

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Before you begin, choose where you will keep your setup, on a table with some indirect sunlight or under house eaves is best.  Once the tub is full of water it is very difficult to move the system.  You can also grow indoors under light if you want, I don't because I live in Hawaii and we have a year round growing season that allows me to use good ol' sun light.

Step 3: Time to drill

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With the Kraty method of non-circulating hydroponics it's important to remember that one gallon of nutrient water per plant is an optimal ratio when growing lettuce... so with the under the bed storage box I used, I drilled eight, evenly distributed, holes in the lid using the two inch hole saw.  Use the utility knife to scrape off any plastic and smooth out the holes.

This box is a 10 gallon box, but I only fill it up to eight gallon so that there is a space of humid air for the plant roots to derive oxygen since this system doesn't aerate with mechanization.  

I use this type of container for lettuce because the roots are shallow and I want a good amount of space for my plants to grow.  There are other types of totes that hold the same amount of water, but the shape and depth aren't what I considered optimal for lettuce growing.

Step 4: Optional water monitor

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I like to keep track of the water level in my reservoir, so I also drill a 1/2 inch hole on the side to insert a tube to monitor what's happening on the inside.  If you decide to include this step you have to be very careful drilling the hole.  

I think starting with a small bit and graduating to larger ones until you reach the 1/2 inch bit might be best if the plastic is stiff.

I've cracked the plastic a few times and had to use food grade plastic epoxy on the damage in order to use the container.  It's not too big of a deal because you still need to paint the container and the repair will be camouflaged.  

Step 5: Now for the painting

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Painting the box is very important because if sunlight reached the nutrient water algae will grow, eat the nutrients and starve your plants.  Also, I would not recommend painting the boxes before drilling the holes because the paint could scratch off.  I encourage you to use the primer, the paint seems to better adhere to the smooth plastic when you use the primer and follow the instructions on the can.  

Finally, I would also recommend that you tape the holes you just drilled (lid and container) so that you can keep the inside of the box as clean as possible... this is where your plants eat after all!

Step 6: Optional step continued

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If you decide you want to monitor the water levels this is where you insert the rubber grommet, the elbow and the vinyl tubing.  The thing about this process is that everything is VERY tight so that water doesn't leak.  

To get a snug fit with the vinyl tubing (and to straighten it out because it probably was coiled when you bought it), dip it in hot water and attach to the elbow and then hold the tube straight until it cools down.  

Insert the elbow into the hole with the rubber grommet... be patient, this isn't going to be easy!

Should the grommet leak just use a little silicone to seal it.

Step 7: Measuring your reservoir

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So now you've got your lettuce bed ready to fill.  What I recommend is that you measure the water levels up to eight gallons so that you can use the garden hose and mix your nutrient right in the reservoir once you have it in place.  

If you don't have the monitoring tube, fill the container up to four gallons and mark the inside with a permanent marker and then fill up to the eight gallons and do the same.  

If you have the monitoring tube, mark the outside per gallon.  

Make sure you do this on a level surface so that your markings are as accurate as possible.  This important so that when you add the nutrients to your water it's the right amount of food for your plants.

**I should take the time to say that my husband thinks we should only fill it to seven gallons to created a bigger air gap between the lid and the water... I haven't noticed any negative results (such as drowning) with eight gallons.

Step 8: Now adding the nutrients

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I use a brand called Chem-gro Hobby Formula 10-8-22.  It's a powdered nutrient that I've been very successful using.  Also, as I understand it, it is the formula Kratky used when developing this method.  At first I was worried because of the word "Chem" in the title, but I called the company, Hydro Gardens, and they explained that it's just the brand name and that their product is not chemically altered and it doesn't have extra chemicals or anything like that... You can use any brand of nutrient you like, just follow the directions.  

After you've added your nutrients to the water you have to test the Ph to ensure it's what is recommended by the manufacturer.  The Chem-gro brand has buffers in it so the Ph is always spot on.

I found this to be an important step because I use city water and the Ph is 8.1-8.5 making the water too alkaline for the plants to take up nutrients.  If you use rainwater this shouldn't be a problem.

Now put the lid on your new lettuce bed.

Step 9: Time to plant!

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Ok, you've found a location for your lettuce bed, assembled it, filled the tank and added the nutrients... Now for the fun stuff!

Fill each net cup with perlite and stick it in one of the holes you drilled in the lid.  Eight gallons of water and eight net cups with perlite.  Some people use a vermiculite/perlite combo, but I use 100% perlite... the preference is yours.

Place the strap around the middle to hold the sides of the container in place when it is full of water.

Seed cups with romaine, mesclun, arugula, cress, komatsuna, bok choy, chard, mustards... a few seeds per cup.

That's it... Watch them grow!  If one does not sprout after a while yet all the others sprout, either move a double seedling or replant the cup with seed.  You can harvest the outer leaves when they get big enough or cut the whole lettuce.

You could plant one tub and maybe two weeks later set up a second container.  Ingrid's family of four eats big salads every night from one box  a week, and my husband and I can eat from a box for two weeks.

I've also learned that when the lettuce bed has used up all of its nutrient water (because of heat or other unconsidered conditions), but you're not done harvesting, you can refill the container halfway with four gallons of nutrient water and keep going (that's why I marked the lettuce beds at the four gallon mark)...

I mix four gallons of the the nutrient  in a five gallon bucket and pour it in (after I empty the rest of the water from the container of course!).  The key to replenishing a reservoir you make of any kind is that you have to let half the roots remain exposed to the air so that they can absorb oxygen otherwise, your plants will drown.

Step 10:

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I've also grown tomatoes in 18 gallon containers, cucumbers in a 32 gallon garbage can, okra in five gallon buckets (replenishing with 2 1/2 gallons of nutrient water as needed), and squash in 10 gallon containers using this method and have had great luck!  

I'm also going to plant sugar peas and green beans in five gallon buckets... I'll update these instructions once I have results.

Enjoy!

Oh, and thanks, Ingrid, for helping with my setup.  You're the best! :)
heavnbnd5 months ago

Okay, so I've done outside circulating Hydroponics for a few years during growing season. I live in mtns. of CA (inconsistent temps from 70 deg. down to teens) so can't do winter outdoors. What temp do these lettuces need in order to thrive? Trying to figure if I can do small greenhouse or need to do indoors. Thanks for the system, it looks great!

Most lettuce types do not do well over about 75 degrees and can tolerate temperatures as low as 45 degrees, so a greenhouse might be an option for you if the night time temps in the greenhouse do not drop too low. I live in Southern California and have trouble growing lettuce because sometimes the temperatures are too high and the plant bolts quickly. A cooler area of California with a greenhouse seems ideal to me. Some types of lettuce like romaine can tolerate more heat but in my opinion its always a much tastier crop if you can keep the temperatures in the 70's. Good Luck!

nah895 months ago

So basically how it differ from other hydroponic measures is that you don't change the water but just replace the plant when it runs out? Would the plants absorb all the nutrients in the water in like a month?

redwolf0076666 months ago
hello every body i am a new beginner hoping to test hydroponics. i am interested in planting hydroponic romaine lettuce. can you please clarify the precise conditions to grow this kind of lettuce.e.g: water ph, temperature, humidity, lighting....?i started my firat batch indoor and my sooo tiny seedlings died after they have stopped growing for a while. any ideas?
thanks
djduncman7 months ago

Awesome Instructable! I'm hoping to use it in the future to make a system of my own. Thanks for posting.

Lots of plastics are problematic when drilling holes in them. One trick I use is to find a piece of metal that is the diameter of the hole I need and heat it with a torch and use it to melt the hole in the plastic. I've never had a cracking problem using this method.

Nick SeanK9 months ago

Hi. a friend of mine has showed this post to me and asked me to give you some guidance regarding a statement you wrote.

"At first I was worried because of the word "Chem" in the title, but I called the company, Hydro Gardens, and they explained that it's just the brand name and that their product is not chemically altered and it doesn't have extra chemicals or anything like that".

You shouldn't worry much about that so much. First of all, basic biology teaches us that plants take in nutrients in their atomic form. Meaning they take in the nutrients in their basic elemental state, namely N, P, K, O, Mg and so on. No matter what nutrient you feed them, whether it is the so-called "organic" nutrients or what laymen call "chemicals", they are all broken down to their simplest state. So it doesn't really matter which type you use, what matters are the contents. As for your confusion on the "Chem" in the title, you must note that every nutrient we feed our plants, no matter which brand, which type, which composition, they are ALL made of chemicals. These chemicals in that form can be harmful if taken by humans, but very beneficial to plants. We ALL take in chemicals, albeit in different forms. Whenever we say the word "chemical", laymen tend to think of hazardous and radioactive mental pictures or scientist wearing Hazmat suits. However, you must note that every single thing in this planet is made up of chemicals. Heck, water is a chemical. So perhaps what you were worried about were actually PESTICIDE or WEEDICIDE chemicals that are usually used in farming to keep away pests and parasites. The word "chemicals" is wrongly used in this context. There's nothing wrong in buying products with the suffix or prefix "chem" to them. What I and other scientist friends observed about the general public is that they tend to buy products with the word "Bio" in it and fear products with the word "Chem" on their names. Unknowingly, both products may have similar compositions and in most cases, they come from the same manufacturer. All of them have chemicals, whether harmful or not. We call this the "placebo effect". So, you shouldn't really be intimidated by "Chem" in any products name. It doesn't matter if a nutrient solution has "extra chemicals" or named "chem" or "bio" or even if it is "chemically altered", but what you need to know is that if certain chemicals IN the nutrients are beneficial/harmful to your plant. If you are thinking of the current technology or scientific advancement which is greatly distinct from the conventional usage of chemicals, you may be thinking of Biotechnology, where we use living organisms to produce or do basically everything. This field, although different from the past scientific innovations, still does use chemicals, but in a very different and special way.

Source: I'm a Scientist (Biotechnologist) by profession. Before going to the Medical and Pharmaceutical field, I used to study Agricultural Biotechnology as part of our pharmaceutical production. Also, hydroponics and aquaponics are my hobbies, aside from micropropagation (plant cell cloning), where I produce a new plant from a small amount of plant tissue in aseptic conditions.

frojasp1 year ago
Hi Dianne,

I have experienced for 9 months in a container of 22 liter 6 bushes chile is important to note that the temperature of the site or the direct sun dehydrate plants since they are consuming more water and the pH increases causing water stress to be controlled providing more water without nutrients, so other results are good.
diannemw (author) 1 year ago
Well, you could replenish the 1/2 gallon container as needed (leaving air space for the roots), but most important is that the container be able to block sunlight. Good luck!
byakkou1 year ago
Hi Dianne,

i'd like to ask some newbie question regarding this method.
i'd like to test this method of growing in recycled water bottle instead.. is it possible? when u said that 1 lettuce would need at least 1 galon of water. what would happen if i din put enough, like only half gallon?
Hi Dianne,

You did a great job on this project. Thank you for sharing.

Do you have any issues with little pests? Here in CA, I have some big green caterpillars that ate all my mint and cat nip, we also have slugs.

Do you have an update on the peas?
DaveNJ2 years ago
Nice job with this instructable. I have tried Kratky in 1 plastic coffee container and my lettuce has not done so well even after 3 weeks. I started with the nutrients touching the bottom of the net cup but the level has never gone down. I have roots 3 inches into the water. I am trying your instruction of reducing the water level so the roots get oxygen. I also plan to make a container just like you show so I can copy your example exactly. Thanks for sharing this. Look forward to more and good luck on your plants!
frojasp2 years ago
Excellent project congratulations.

I used the method of the wick that is very similar, where nutrients to the substrate by capillary rise the problem is that the fuse very easily rot and substrate must be good at holding moisture.

I will put into practice this technique in order to evaluate it, I would like to comment more on solutions in Colombia not get as easy as shown in the article.
stevewan2 years ago
Hi Diane,
I just joined earlier today and read your interesting article.
It is very nice of you to take the time and effort to put that together.
I live in NW AR, our first frost date is the last of October, I plan on trying your method ASAP.
Thanks again,
Steve
diannemw (author) 2 years ago
You're right... that's a very good contribution, thank you!
rrrmanion2 years ago
you could use sand paper to rough up the surface to get the primer to stick even better
rrrmanion2 years ago
you could use sand paper to rough up the surface to get the primer to stick even better
diy_bloke2 years ago
Interesting, but what i dont understand is what happens if the waterlevel sinks below the pots, at a moment that the plants have no roots growing out of the pots yet. It all seems to assume that evaporation and sprouting/growing are all sort of magically connected. Or did I miss something.
CityGirl62 years ago
My brother lives in Hawaii too is always very interested int he farmer's markets here. I'll have to send him this to see if he's ready to grow. Thanks for sharing.
WUVIE2 years ago
This is absolutely wonderful! Thank you so much for such an excellent Instructable!
padsurfdon2 years ago
Diane,
I enjoyed the posting, I also live in Hawaii and am looking into growing our own vegies in the back yard. Vegetables are so expensive here, and trying to live a healthy lifestyle is really "more expensive" food wise. Useful information that may assist me with my initial setups.
Thank you,
Don
rimar20002 years ago
Very, very interesting projects, congratulations.

Holes on plastics can be done with a hot wire or tube, more easily and without break the material.