The test included five different systems: four hydroponics and one control sample. We ran this experiment for three months on a bench in a basement with grow lamps situated to shine directly onto the plants. Each of the five systems contained three different plants including: cherry tomatoes (a model for flowering fruity plants), lettuce (a model for leafy greens), and beets (to represent root crops). All of the containers were solid opaque plastic to keep the light out of the water reservoirs and reduce the amount of aloe growth.
#1: The Drip System: First, we have a drip system. The drip system uses clay pebbles to anchor the plant and delivers the water through an HTPE gardening irrigation system with three emitters. This system delivers water three times per day for 15 minutes each time.
#2: The Deep-Water Culture (DWC): Next, is the Deep-Water Culture. In this trial, the water is aerated with bubbles delivered by an aquarium tube and air stone.
#3: Aeroponics: The third system contains one ultrasonic fogger. These foggers were purchased from a specialty supplier for around $30 each.
#4: The Kratky: The fourth set-up is the Kratky: basically just distilled water and nutrients.
#5: Control Sample: Lastly, basic soil. Miracle Grow potting mix was placed into three free-draining containers (aka water bottles with holes in them) to use as the control. This was watered by hand, but truthfully, some waterings were missed and it got too dry every once in awhile.
Issues with the Experiment:
There were some limitations and problems which might skew the results, including:
(1) The plants in the DWC with the bubbles died early. This wasn’t intentional, but (as we learned) the system goes through water extremely rapidly.
(2) Some of the plants were not given enough time to reach their full potential. For example, the tomato plant in the drip system grew very large but was slower to flower. Unfortunately, the experiment ended before it was given enough time for all of its flowers to fully produce fruit.
(3) Finally, there was an element of human error. Life happens and occasionally the control system wasn’t watered as a result.
What did we learn from our experiment? The most consistent and comparable data ended up being for the tomato plants, so that is the data which will be compared here.
Plant weight: The drip system grew the biggest plant, by far, but was much slower to flower. Unfortunately, because it ran out of water the Deep-Water Culture tomato plant didn’t make it to the end.
Yield: The aeroponic fog-based system produced both the largest and greatest quantity of fruit. The most surprising result was that the Kratky was the second best in terms of fruit yield. Given the simplicity and low cost of a Kratky set-up, it punches well above its weight.
Temperature: (Remember that these were all sitting in the same room, side-by-side.) You’ll notice from the graph that the aeroponic system was very warm. This is due to the heat emitted by the electronic fogger. Meanwhile, the DWC system with the bubbler was by far the coolest because the constant evaporation of water forced by the system is an endothermic reaction which absorbs heat.
Water use: The major differences in these systems was how they related to water use. The DWC with the bubbler by far consumed the most water. The Kratky consumed the least because it’s a passive system which doesn’t really force the air out. With the aeroponics, which was quite close to the Kratky in water usage, the vaporized water is able to condense back into the system so it recirculates rather than constantly intaking new water.
Which System Was the Overall Best?
If overall cost and maintenance are not a constraint, you’re likely to get the best results from an aeroponic-based system. However, in terms of bang for your buck, ease of set-up and use, and the fact that there are no moving parts, the Krafty system is hard to beat.
Hopefully, this has been a useful overview. Don’t forget to head on over and check out our video explaining the science behind each of these four hydroponic systems.
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