After learning about wicking beds in my Permaculture Design Certificate course (which I graduated from last weekend!), I had a hard time understanding how they worked. Here is a great illustration from Urban Food Gardens:
What did not make sense to me was how the moisture got up to the soil even after the water level drops. I had to make a model to demonstrate this purpose using materials around the house. Here is what I came up with:
This is reused container filled about 1/3 of rocks, a piece of landscape fabric, a reused piece of tubing down the side, then cotton from a pill bottle. To make the wicking of water more obvious, I added blue food colouring to the water before pouring it down the tube to fill the bottom reservoir. Additionally, I poked a hole just below where the rocks and fabric meet for drainage.
After an hour or so, here is what it looked like:
After 2 hours and a bit of compaction to make the cotton fibers touch each other better (shredded paper may work better) :
At 2 weeks after construction and adding water, the cotton has stayed moist even though the water level has dropped below the fabric level. The main idea behind this design is that the plant roots will grow down toward the moisture, hence stronger and more resilient. Watering from the surface produces roots that extend outwards (not down) because the whole container or bed rarely gets watered thoroughly enough to allow the roots to grow down. This design is particularly successful in very arid climates or for lazy gardeners who only want to water once a week or so.
I deem this experiment successful and now have a much better understanding for how wicking beds work.
Try this experiment with your children, then make a Global Bucket or larger scale wicking bed if you are so inclined!