A closer look at wicking boxes: In the home salad growing system, I am using wicking boxes. I make them from store bought materials for about £4.50 each, but they can absolutely be put together from old reused parts like grocery crates and recycling boxes. In short, the idea is to have a water reservoir at the bottom of a container, but to also have no more than about 15% of the soil surface area sitting in that water reservoir, and to have a little gap for air exchange too. I have done this in 35L boxes, with a water out hole (and hose length) at about an inch high, and an upturned basket to keep the bulk of the soil elevated. The soil itself "wicks" up the water, making it available to growing plants. After the stage shown in the above photo, I drilled several holes into the top of the upturned basket (basket with holes already in are much easier, but these are what I have) and rested a cut up drinks bottle on top to allow me a direct watering path to the reservoir, without needing to specifically water top down through the soil surface. When I have recently seeded I still top down water until they have germinated, just to make sure. Why bother? I severely doubt there is much commercial viability in this system (unless you have access to a ton of free parts), but on the home scale it has loads of advantages that I feel makes them very forgiving. The water reservoir allows you to prime a box so that you can leave watering for a few days even in the peak of summer, which is great for busy schedules and holidays. They can also store more water for longer during rain events as well, giving you less work. The bottom up wicking/watering method also reduces surface reflection (compared to conventional top down watering) which can scorch greens, and as a salad growing system that would be quite a pain. The reduced surface wetness would also reduce water evaporation, fungal issues, and snail/slug activity. The bit with the bottle in also acts like a slug beer trap as well, especially if you are fertilising with stuff like molasses water into the reservoir, so they can be removed manually pretty easily. They're not a perfect system, for example the cost involved if you are buying in parts, and the risk of shattering/breaking can be a pain, but I would say for home scale stuff like salad, herbs, tomatoes, grapes etc (stuff you see a lot of in hydro/aquaponic systems) it works really well.
