The most water was held in woodchips and the coarser two soil mixes, but these materials would probably be more compacted when used in a wicking bed and thus probably hold less water. I measured this by filling a container of a known volume with the material, then adding water until it came to the top of the container, level with the top of the material. The graph shows how much water each material can hold, as a percentage of the volume of the material. The more water that is stored, the longer you can go before you have to add more water to the wicking bed. The second is to provide enough spaces between the particles to store a reasonable amount of water. The ability of various materials to do this was discussed in an earlier blog post.

The first is to wick water up into the growing media.

The material in the reservoir layer needs to do two things.

At the moment the lettuce growth is spectacular. I'll report on those results in the future. I currently have the same wicking beds planted with lettuce and am recording more detailed measurements of soil moisture at various depths that should allow me to draw more certain conclusions about the better materials for wicking beds. Gravel does not have good wicking properties and even though the reservoir was 200mm deep, only part of the water was able to wick up into the growing medium. In my next experiment I have replaced the perlite in the WaterUps with the cocopeat mix that I know does wick well.Īs I hypothesised before the start of this experiment, 10mm gravel did not perform well as a reservoir material. I filled the hollow legs of the WaterUps with coarse perlite and have subsequently found that this does not wick as well as perlite with smaller particles. I am not drawing any conclusions on the WaterUps product from this experiment. Washed sand in the reservoir layer appears to be a good choice and sand would not suffer from decomposition. I have had better long-term results using a 50:50 mix of garden soil and compost through the whole wicking bed but I haven't done a controlled experiment to test this yet. I have some concerns about the long-term performance of this design since I have found in other wicking beds that I have built that potting mix/compost in the reservoir decomposes anaerobically and deteriorates into a black sludge. Based on these results, the simple design using the Cocopeat Mix for both the reservoir and growing layers is best.

Wizkid in my bed refix colmix