About three weeks ago, I started a few tomato seeds, and a single salad seed on a damp paper tissue. A couple of days after sprouting, I re-planted them into a non-circulation hydroponic set-up based on the principles described by Professor Kratky from the University of Hawaii, often referred to as the Kratky Method.
The set-up consists of an 80cm balcony planter without holes (the kind where you’re supposed to drill drainage holes yourself if you want to use them for soil gardening) filled with nutrient solution. As top cover, I used 2 half length (40cm) trays meant to be put under 40cm planters of the same type. The trays are a few milimeters longer than the planter, so for perfect fit, they needed to be shortened by s few milimetres with a saw.
Openings of 5cm in diameter were cut-out in the trays to house 6 net-pods with rock-wool and the plants. At the start, about half of the net-pods should be immersed in water. Later, water level drops as roots get bigger.
While making the holes, the trays cracked in a few places, so the result is not very aesthetic, but the whole thing still holds together. When filled with water, the container becomes a bit wider due to the pressure of water against the sides, which is why I tied a nylon string around the center of the pot. Overall, there are about 2 litres of water-nutrient per plant.
So far, the tomatoes have been doing really well in the this set-up, being at least twice as big as plants from the same batch (sprouted at the same time) that I placed into soil on the balcony (left image below).
Potential problems and obstacles I see in the near future
Two liters of nutrient solution per plant is probably not enough to bring tomatoes to fruit without re-filling, so some topping-up will be necessary. Another challenge I’ll soon have to face will be providing a trellis the tomatoes can climb on. Further, I am not sure if the space left for roots in the hydroponic set-up is big enough for six plant in an 80cm pot.