This document was provided by Lance Edwards as an outline of the process of building a 100 Fold Vegetable Garden using Foundation for Farming principles. He includes a description of wicking bed technology by Colin Austin
The irrigator’s dilemma
If the irrigator applies frequent but shallow irrigations much of the water will be lost by evaporation. Applying deeper but less frequent irrigations is more efficient but can easily lead to loss of water past the root zone, valuable nutrients and can cause environmental pollution.
The wicking bed is a solution to this problem. In its simplest form a water reservoir catches any excess water from above ground irrigation and feeds it back to the plants as they use the water. In more advanced versions water is fed directly to this reservoir so all the plants water needs are supplied from the reservoir by wicking action.
The essential feature of the wicking bed system is the water reservoir filled with a coarse aggregate which is saturated with a significant volume of water which is not held tightly by surface tension. This water is free to wick up to the layer of soil containing the root zone. This contrasts with the traditional system in which a much smaller volume of water is held in the soil below the root zone.
The restraining surface tension forces in this soil mean there is very limited ability to wet the soil in the root zone above.