At the request of a connection in the Middle East, I have gone back in my development mind to reclaiming desert using urban wastes. The basic concept of “submerged bed reservoirs” indicates that the very top layer of soil is not much use in desert soils in the sense that it will often be too high a temperature for root and biological activity, lose water quickly and have its organic matter rapidly oxidised. However, it does have a real value as an insulating layer. So, the next step is to design the depth and material of that insulating layer. The second step is to design a submerged bed to hold water. Sand will hold its own weight of water. Clay twice its own weight. Compost with high organic matter will hold up to ten times its own weight sometimes more up to 16 times. So, design the insulating layer, the amount of compost and the irrigation distribution and quantity, so as to establish the crop (so as to allow its roots to tap into the submerged bed) and, at the same time, charge up the bed (reservoir) to minimise or eliminate the need for further irrigation before harvest.
Logically, it is possible to reduce irrigation need by a factor of 10, maybe 20 because evaporation is dramatically reduced. The submerged bed? Compost made from urban wastes.
Bill Butterworth 19 December 2015