What is Kratky Method Hydroponics?

Most of the information out there about getting into hydroponics mentions the Kratky method, but most don’t really get into what it is. The name sounds intimidating, but it turns out that the Kratky method is one of the easiest hydroponics systems on the block.

We broke down the Kratky method for you from the definition all the way to what it takes to grow leafy greens in a homemade system. Let’s take a look!

kratky hydroponics

What is the Kratky method?

The Kratky method is a version of deep water culture hydroponics that just happens to eliminate all of the electrical components that can make a deep water culture setup an expensive venture to dive into. Removing the pumps and air stones from a traditional deep water culture garden takes the setup from an active system to a passive one. The lack of active pumping is the key point of the Kratky method, which is by definition a passively managed hydroponic garden.

Looking at a Kratky method system, the main components are a tub to hold the water, a way to suspend or float the growing pots, and a lid for the tub. The tub is filled with water, and the water is primed and fertilized. Once the proper water chemistry is established in the water tub, the growing pots can either be suspended from above or floated on some type of growing tray so that the bottoms of the roots are submerged in the water and the tops of the roots are exposed to the air.

At this point, the plants are prepared to begin growing, and the gardener can put a lid over the water surface and walk away. Water chemistry only needs to be re-established if the farmer has to add more water to the system.

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How does the Kratky method work?

The basics of the Kratky method follow the same idea as deep water culture hydroponics: seeds are sprouted, the seedlings are transplanted into the growing cups, and then the plants use the fertilized water as its hydroponic growing medium. The places where the Kratky method departs from traditional deep water culture is in how the plant gets air to its roots.

With the air stones constantly pumping air through the water, a plant in a traditional deep water culture garden can have its roots fully submerged in the water and still receive oxygen, thanks to the bubbles from the air stone and other dissolved oxygen. Using the Kratky method, there are no air stones and no air bubbles, so the plant’s roots are only partially submerged to allow for air access through the upper portion of the root system.

Although it seems counterintuitive that something buried in the ground would be exposed to air, plants receive oxygen in soil farming through dissolved oxygen in rainwater and the penetration of air after the soil begins to dry. Similarly, active hydroponics systems dissolve oxygen into the water through aerating or misting the water.

In passive hydroponics systems, such as the Kratky method, the water is stagnant and is unable to re-oxygenate the water as fast as the oxygen is absorbed by the plants, so the exposed roots make up for what the water lacks. If a plant is not receiving enough oxygen to its roots, the plant will eventually suffocate.

As the plants continue to grow, the roots get longer and reach deeper into the tub. Meanwhile, the water level goes down as the plants absorb water and as minute amounts of the water evaporate off. This results in the root systems always having a proportionately appropriate amount of root exposed to air and exposed to water to ensure that the plant doesn’t become deprived of oxygen.

Without extra water inputs, the water chemistry remains stable, and the plant thrives off of the fertilizer dissolved in the water during the initial setup process. If the plant choices require longer growing times than the time it takes for the water to disappear from the tub, the farmer can choose to add additional primed and treated water as necessary.

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Kratky method pros and cons

Pros

Cons

Very cheapNot a practical large-scale setup
Easy to maintainMore vulnerable to pests
Perfect for beginnersNot great for large/long plants

Benefits of the Kratky method

The Kratky method is cheaper to set up than other deep water culture systems. With using a passive system, all of the most expensive pieces—the pumps, air stones, etc.—of the hydroponics setup are eliminated.

Kratky method gardens are cheaper and easier to maintain. Without the electrical components of the garden, you no longer have to worry about electric bills associated with the garden. Additionally, the water chemistry is much more stable, so you don’t have to test and adjust the water as often as with active deep water culture gardens, and you have a lower water cost, as there is no excess water being circulated.

When it comes to beginner gardeners or those that don’t have a lot of time, the Kratky method is a good way to test the waters of hydroponics or grow some fresh produce for the family without making it a big part of your day.

Disadvantages of the Kratky method

For larger operations, the Kratky method isn’t very practical. Anything larger than a backyard garden will grow much more efficiently and successfully using active hydroponics systems.

Gardens using the Kratky method are more vulnerable to pests than active hydroponics systems, because of the stagnant water. Many insects rely on stagnant pools of fresh water to lay their eggs and mature into adults, with mosquitoes being a big one. If your Kratky method gardens are outside, you risk farming mosquitoes and other insects alongside your produce. Making sure that you include a type of lid on your setup to prevent insects from laying in the water can greatly reduce the risk of pests, but it is not always fool-proof.

Larger or longer-growing plants tend to do better in other hydroponic setups. The best choices for the Kratky method are plants that will be ready to harvest by the time the water level in your tub in getting low for the first time.

kratky method hydroponics
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Tips for building a DIY Kratky method setup

Building a hydroponic garden that runs using the Kratky method is relatively simple: get a water tub, suspend your plants, watch them grow. Here’s a few things to keep in mind as you choose your materials.

Make sure you’re familiar with the plants you’re planning to grow. The plants that grow most successfully in gardens using the Kratky method are fast-growers like leafy greens. You can grow other plants that don’t fit the bill for fast-growing, but you may find that other systems work better for you if those are your primary crop.

Check on the roots rather frequently, especially if you’re newer to hydroponics. Most of the time, you can build a garden with the Kratky method, leave it, and you’ll be fine, but checking on the roots makes sure that they aren’t getting waterlogged or are unable to keep up with the dropping water level.

One way to keep track of root progress is to keep a photo journal of what they look like pulled out of the water. Take note of the color, length, texture, and number. Compare your photos to what the healthy roots looked like when they first went into the hydroponics garden. Healthy roots tend to be lightly colored and firm. The length and number of roots depend on the age and type of plant. As a general rule, roots should be getting longer and more numerous as a healthy plant grows.

Use a lid. This has been said before, but it’s good to say it again, because no one wants to walk outside to harvest their Kratky hydroponic lettuce and be attacked by a swarm of hungry, newly-hatched mosquitoes. The only thing that would make that worse is knowing that you’re the one who gave them a place to lay their eggs, which would exactly be the case if you’re not using a lid on your hydroponic Kratky method garden.

If you’re using a tub with a latching lid, you can simply cut out holes large enough to hold the growing pots without falling through and snap the lid on. The lid will keep the plants suspended and will keep the pests out of your water.

Be sure to completely prime and treat your water before planting. Your pH should be within the range acceptable for your crop—usually between 5 and 6—and you should have fertilizer dissolved into the water at the proper concentrations. To check your pH level you’re going to want to get a good pH meter for hydroponics, and make any adjustments accordingly.

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Growing leafy greens with the Kratky method

Begin your growing season by choosing a high-quality seed and sprouting them outside of the hydroponic system. Most people will use individual sprouting cups and place a few seeds into each cup. Some seeds won’t germinate and others will be weak, so having several seed attempting to germinate in the same cup will ensure at least one strong seedling.

Thin the cups out to one seedling per cup once you are able to identify the strongest plant. Once the seeds have become seedlings with enough roots to fill the sprouting cup, they are ready for transplant into the hydroponic system.

Before you transplant the seedlings, make sure to check the water chemistry, water levels, and that the growing cups are placed at the correct height. Transplant the seedlings and adjust their height or the water level until there’s a few centimeters of root out of the water.

At this point, you can usually just let the plants grow on their own. Check the roots, water chemistry, and water levels as necessary and make adjustments to your garden. Once the plants have matured, they are ready for harvest. You just successfully harvest your first Kratky method crop!