In reply to Jed Rothwell's message of Fri, 28 Sep 2007 14:28:38 -0400: Hi, [snip] >The Israelis have pioneered >subsurface irrigation which reduces consumption by about 2/3rds.
Subsurface irrigation means laying pipes etc. which can be expensive. There is a much cheaper method, which should be almost as effective, and may well help considerably, particularly in the developing world. It is night time irrigation through surface channels. Channels on the surface have been used to irrigate fields for millennia. If the water is applied to the channel system after the ground has cooled, say around midnight to 2 AM, and all of it soaks into the ground, then it will all be subsurface anyway, before the Sun rises the next day. The trick is to ensure that not too much is applied. All of it needs to soak in. If any is left on the surface, then it will be subject to evaporation during the day. Even so, the surface is going to remain moist, and this small amount will be lost to evaporation, which makes the method a little less efficient than true subsurface irrigation. Getting the applied amount right, will be a learning experience for individual farmers, but well worth the effort in the long run. Needless to say automatic dispensing systems can be developed, which even though expensive for a poor farmer, would still be a much smaller investment than a whole pipe network. Those too poor to afford even this, can always do it manually. Of course covering the ground with "litter" also helps, as water falls through between the matter, but sunlight is prevented from reaching moist ground underneath. Regards, Robin van Spaandonk The shrub is a plant.
