Hydroponic Systems: The Kratky Method
by Natalie Jones
March 18, 2019

When it comes to cost-effectiveness in hydroponic systems, the Kratky method is by far the most efficient. It works by providing a plant with all the water and nutrients it needs from the beginning to harvest time.

Initially, the bottom of your plant holder is submerged under water. As the plant grows. Its roots also gradually extend downwards as the water level lower. The increasing gap between the plant and water level creates room for oxygen, eliminating the need to bubble air into the water, as this is automatically done for you.

If planted using the Kratky method, a lettuce plant only uses approximately one gallon of water. When farming on a higher scale, more space is required. You’ll need enough surface area for your plants and storage space for water. That said, there's no harm in crowding the plants when using the Kratky method on a large scale since there's enough water and nutrients for every plant.

How to set it up

Using this method is not complicated. Here are some steps you can follow:

Step 1: Germinate Your Seeds

It goes without saying that you have to germinate your seeds first. Soft and porous material such as coir bundles, Rockwool cubes or thick cotton swabs makes the best growing medium to use.

Once you wet the medium, poke a hole in the top and drop some seed inside it. It's recommended you drop multiple seeds in a single cube to ensure that at least one will germinate.

Also, remember to keep the seeds in a humid place. It's important that the medium stays damp enough to sustain the plant. You also don’t need light at this stage. It’s okay to even store them in a closet or enclosed space.

If you get this right, the shoots should pop out within three days.

At this stage, light is necessary. You can use grow lights (LED bulb or T5 tube light). Natural light from the sun will also do.

After about 10-14 days, the first set of true leaves will have formed.

Meanwhile, you can set up your growing bucket.

Step 2: Set up your growing bucket

It doesn’t matter what kind of bucket you use. Any large container or large vessel can work. However, any vessel you choose should have a removable lid. Also, remember that you need at least one-gallon capacity to hold enough water for one lettuce. Anything smaller than that means you have to refill as the water level drops.

Next, make a hole on the lid. It should be just the right size such that your net cup won’t fall in all the way. To get this right, it is best to make a smaller hole than you need at first, using a box-cutter. You can then trim it lightly till you get the right size.

If you intend to grow your plants outdoors, you’ll need to prevent sunlight from penetrating inside the bucket. Exposure to sunlight leads to growth of algae and other bacteria.

If you’re growing indoors this won’t be a problem.

Once your seeds have germinated the next step is to transplant them into the bucket you just set up.

Step 3: Transplanting Your Shoots into the growing mixture

The ideal time for transplanting is when your seedlings have developed leaves with visible veins. These should not be confused with the leaflike structures that appear when a seedling sprouts.

First, you drop a layer of growing media e.g. hydroton, into the bottom of a net cup. Then pick your seedling together your planting medium at its base – rockwool in this case- and place it inside the net cup with the hydroton. You should be careful while handling the seedlings as they are still fragile at this stage.

You should then fill up the gaps that remain by adding enough hydroton in the net cup to cover the Rockwool. The leaves should however be left exposed.

Fill the bucket with water to an extent where up to 1inch of the net cup would be submerged in the water once it’s placed in the hole. You should also measure the amount of water you use, to calculate the amount of nutrient solution to put in.

Once you’ve added the nutrient solution, place the net cup inside the hole you cut out. You’ve now completed your Kratky setup.

You should check the water level, once in a while, to make sure the roots can still reach the solution.

Step 4: Wait for the Plants to Grow

You should expect a fresh head of lettuce after 4-5 weeks. The growth period depends on the nature of the plant.

As you wait, keep checking whether your plants are getting enough light and whether the nutrient solution is enough.

Light Setup Options

As long as you have temperature and lighting under control, you can grow plants using hydroponics at any time of the year, no matter how cold it gets in winter.

Poor lighting makes the plants grow long and their stems weak. This happens as they stretch towards the light source. When using artificial light, you should therefore make sure the light is very close to the plants.

For the best results, use a holder that will fit 3-4 tube lights then hang them from a chain. If you prefer LED bulbs - the cheaper option - use a holder that will reflect most of the light downwards. You can adjust the height as your plants grow taller.

What can you grow in the Kratky system?

You can grow anything using the Kratky system. We used Lettuce because leafy greens don’t require a lot of maintenance to grow. It’s recommended you stick with plants that don’t need a lot of care such as Spinach, Kale, Mint, Coriander, Basil and other herbs. These ones just need enough water and nutrients to keep them going.

Flowering plants require extra care. They also occupy a wider space so you’ll need larger containers.

Before you decide to use the Kratky method, you should first consider the maintenance required until harvesting.

Final Thought

The Kratky method can work anywhere, indoors or outdoors. While natural lighting is better for plants, there’s also the risk of exposure to pests if you plant outdoors.

For flowering plants, pollination has to be done manually if you decide to plant indoors. If you grow outdoors, pollination will take place naturally.

It’s clear that each method has its advantages and drawbacks. But that does not matter as long as conditions such as temperature and light are sufficient.

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