I used to think that hydroponics needs a lot of hardware, such as tubes, air-stones, multiple containers, and the like, and of course electricity to power the pumps moving water or air or both. To my delight, it turns none of this is strictly necessary. In fact the only thing you need to grow certain plants, including salad greens, is water, nutrients, support for the plant, and most importantly for this non-circulation method, a space filled with damp air between the water-level and the container cover, from where hanging roots can absorb oxygen. If the plants’ roots were completely submerged in water, chances are growth would be limited, the plant would be weak, and might even die altogether, effectively ‘drowning’.
This particular set-up consists of a single 11 liter Samla box from Ikea with a corresponding lid (less than 2 EUR altogether), into which I drilled 5 holes to house 5cm net-cups (see photos). I used the remaining bits of plastic cut out from the lid (as well as a few yogurt bottle lids) to block light from reaching the surface of the substrate to prevent algae growth (the algii like to ‘steal’ nutrients from the crops). As fertilizer, I use the GHE Flora Series hydroponic nutrients, which consists of MICRO, GRO and BLOOM elements, out of which I only use the first two, since flowering or fruiting is neither required, nor desired in salad greens, unless you want to collect seeds for next season).
Then I re-planted small seedlings with a single set of leaves into 4cm rockwool cubes. In turn, I placed the rockwool cubes into the net-cups, with about half of the cups submerged in the nutrient solution. Unlike in my previous experiments, this time the size of the container (11l) should be sufficient to ensure that no further adding of water or nutrients will be necessary (over 2l per plant should be enough, especially in this year’s cold weather). As the water level drops and the air-pocket gets bigger, roots grow longer, thus still reaching into the water-nutrient solution.
About a week after the first plants, I added a slightly older Crebiata Catalogne salad plant (previously kept in the tomato container) to the same set-up. This wasn’t the wisest thing to do, since ideally, all plants in a Kratky system should be of roughly equal size and age to let them compete for ‘resources’ in a level playing field. Otherwise the strongest plant usually establishes the strongest roots and over-grows the others. In my case, this ‘alpha’ plant was the newly re-planted Crebiata Catalogne (in the centre) , which already had a strong root-ball at the moment it was introduced among the smaller and weaker seedlings.
Notwithstanding, about 3 weeks later, the whole ‘salad plot’ looks almost ready for the first harvest:
Next time, I will try to plant everything at once, and stick to placing a single variety (or very similar varieties) into the same space.