What is the Kratky Method of Hydroponics?
The Kratky Method of Hydroponics is a way to grow food without the use of water or air pumps. This method allows the grower to be completely off the grid and grow healthy nutritious edibles in areas where electricity is unavailable or even non-existent.
Before I dig into what makes the Kratky method work, let me give a very basic explanation of hydroponics. Hydroponics is a method of growing plants without soil, using water to deliver the necessary nutrients and minerals for plant growth. Most of these systems rely on air pumps to transport the water and nutrients from a reservoir to the plants.
Flood and Drain vs Deepwater Culture
There are two primary methods of growing hydroponically: Flood and Drain (also called Ebb and Flow) and deep water culture. There are of course variation in these two methods, but all of them rely on either an air pump or a water pump and many rely on both.
The Flood and Drain method requires a pump to lift water into the grow bed where it temporarily immerses the plant’s roots in the nutrient rich water. Once the grow bed is full it triggers a drain and the nutrient solution returns to the reservoir. This flooding and draining occur at regular intervals to ensure that the roots are never completely dry nor submerged long enough to cause the plant to drown.
Deepwater culture, on the other hand, uses a floating raft system which suspends the plants above a reservoir tank filled with nutrient solution. The roots are submerged continuously, but oxygen is pumped into the solution at a sufficient rate to keep the plants healthy.
Both of these systems rely upon heavily electrical power to keep the plants alive. A loss of electrical power with either of these systems could potentially result in disaster for the plants. The Flood and Drain system would die as the roots dry out and the plants starve to death. The Deepwater culture plants would suffocate.
The Kratky Method Solves This Problem
If you want to grow vegetables without relying on electricity for water or air pumps, the Kratky method might be just what you’re looking for. As you might have guessed the method is named after the man who developed it – B.A. Kratky. I downloaded and read a paper he wrote titled “A Suspended Net-Pot, Non-Circulating Hydroponic Method for Commercial Production of Leafy, Romaine, and Semi-Head Lettuce.” You can get that here.
My Kratky Experiment
After reading about his work, I had to try it. In a nutshell, the method requires a container that can hold enough nutrient to sustain the plant for its production life. For a determinant tomato plant that would be about 45 gallons. For a head of lettuce, it would be one gallon. I had several lettuce plants already started in a seed tray and I only had room for 8 of them in the garden. I took the least healthy one and transplanted it into the top of a gallon milk jug. The milk jug was filled with a mixture of 20-20-20 fertilizer and micronutrients. It was not the optimal blend for this method, but it was what I had on hand.
This is a picture of the head of lettuce a couple of weeks after I transplanted it. The milk jug is wrapped with a FedEx shipping bag. This is used to block sunlight from the nutrient solution and the roots.
Kratky says a head of lettuce will consume approximately one gallon of nutrient solution in 5 weeks and be at maturity at that point. I left this jug unattended for the entire period. At the end of 5 weeks, I removed the lettuce from the jug.
While it is not the largest head of lettuce, it is quite impressive. The roots are almost pure white and as you can see, well developed.
The milk jug only had a couple of tablespoons of nutrient solution left in it. So, the timing was spot on as well.
Try It Yourself!
What an amazing discovery. For the next phase of experimentation, I will use the recommended nutrient solution and plant a full flat of lettuce. I will plant this just before I leave for summer vacation and hope to return to a bountiful harvest. That post will come along around the middle of July. In the meantime, if you are interested in trying this method yourself I recommend reading the article above and also take a look at this instructable