The new method is basically to take a piece of PVC pipe or
hose, cut about an inch off, slice the cut-off tube so that this sleeve can be slipped over the main section of pipe or hose, and then poke a hole in the other pipe so that water under pressure can drain out of it, yet it
doesn't flow freely because of the back pressure of the sleeve. 
Note: I used to think that this was a good idea but have
since found that drip tubing is cheaper and more effective, if you can only identify a supplier in your country!-Trey
Benefits:
- Relatively inexpensive. "Colorado-based International Development Enterprises has developed a drip system that costs just $50 per half acre ($123 per half hectare), 10 to 20 percent of the cost of traditional drip systems. The keys to keeping costs down are simple materials and portability: instead of each row of crops getting its own drip line, a single line is rotated by farmers among ten rows."
- You make one length of pipe, and then you water a row of individual plants until the water has wetted the ground about six inches deep, and then you move that pipe. A lot of work for Americans, but I think it makes sense in the developing world.
- Requires less water (ie, less money for a pump, less time pumping, lower water bills for city water.)
- Controls weeds because they don't get the water.
- Waters the base of the plant: great! because the pesticides (natural or chemical) that you apply to the leaves of the plant will remain.
- Fertilizer (again natural or chemical) can be put in the elevated container, to provide constant fertilization. Example, you immerse a sack of manure in your supply container, and the good stuff in it slowly leaches out into the water.
- Avoids the salinization of the soil. (In arid lands, water constantly evaporates, and the amount of salt in it becomes concentrated over time. Eventually, the water will dry up and the salt crystals can be seen on the soil. It was a huge problem in Mauritania, and it can be avoided.) I have read that drip irrigation can even carry the salt away, revitalizing the soil.
Directions:
Get some PVC pipe (small, cheap stuff-I think 20mm?) If you can hook
this pipe up to some sort of elevated container (best is about 10 feet (3 meters) above the ground of water via a hose or something, you can make a cheap drip irrigation system. - To do this, drill holes spaced about the distance between two plants, say, 1 meter apart (in some places you may have drills, otherwise, you can use that reamer blade on your Swiss Army Knife, or get a coat hanger, stick it in a fire to heat it, and pierce the pipe),
- And then with another piece of the same size of pipe, cut off about 2 cm sections,
- Slice those sections lengthwise, and then they will slide over the pipe that you drilled holes in.
- Make sure the holes are smooth on the outside, so they make a good fit with the sleeves. The closed end of the sleeve should cover up the hole.
- Voila! Instant cheap drip irrigation, which can be used with clean or dirty water! I think it has a hell of a lot of potential, and it is the best idea I've seen in a long time. Try it out! (And let me know how it went!) When the holes clog up, all you have to do is shift around the sleeve to clean them out. This way, you can efficiently use that precious water, fertilize your plants, avoid washing off precious chemical or natural pesticides and prevent salinization all at the same time.
Get some PVC pipe (small, cheap stuff-I think 20mm?) If you can hook
this pipe up to some sort of elevated container (best is about 10 feet (3 meters) above the ground of water via a hose or something, you can make a cheap drip irrigation system. 
Some excellent comments I received via email from irrigation specialists:
Dear Trey,
If you can place the water tank about 10 feet off the ground you'll have approximately 4 psi to work with. Not as much as I'd like (prefer 10 psi), but a start to water your crops. You can put a filter on the output - such as a good screen filter - but you'll have to clean it often. And it will restrict the flow rate some, as you probably already have guessed.
The conversion for height of water to pressure is:
1 psi = 2.308 feet of water
So, if your tank is 8 feet above the field, you'd have 8 / 2.308 = 3.46 psi at the field (not counting friction, of
course). You can use this to get the pressure you need provided that you can get the tank high enough!
>I became interested in drip irrigation because my >research told me that it would
>
> -avoid salinization of the soil (a real problem in
> Mauritania)
> -use less water more efficiently
> -avoid rinsing off pesticides applied to the plants
> -allow direct "fertigation"
All true. The salinization benefit comes from the water being applied to the root area of the crop. This in turn "leaches" the salts away from the crop roots a little more during each successive irrigation. Creates a low-salinity
zone for the roots. Of course, it all mixes back in when you till it, but it's surely a benefit.
Application efficiency of drip is 90 to 95% - that is, that much of the water actually gets into the soil. Sprinklers,
by comparison, can have an efficiency of anywhere from 70% to 85%. So yes, you get more of the water you pumped into the ground to the plant with drip.
W. Bryan Smith
Area Extension Agent - Irrigation / Water Quality
Clemson Extension Service
P.O. Box 160, Newberry, South Carolina 29108 USA
Office: 803 276-1091 FAX: 803 276-1095
E-mail:
Dear Trey,
Here is a little variation that could give the people a
little more control, as in uniformity of application, of the system. After the hole has been drilled rather than using a sleeve to cover the outlet you could use a length
of PE spaghetti tube that would be cut to a specific length to allow for the head differential and thereby making the application rate uniform. These tubes could be removed for
cleaning if necessary and reinserted without tools. This way there would be uniformity of both water and fertilizer.
When I say spaghetti tube I'm talking about a small diam.
PE (polyethylene) tube that is just a bit larger than the hole in the pipe. Since the PE has a memory, when you insert it into the pvc pipe it will compress and then expand again once inside the pvc. You can calculate the
head loss per inch or cm through the PE to reduce the exit pressure. In this way you can control flow also. Since it is just a length of straight PE tube it can be extracted
and blown out to clean it. The tube comes on spools and can be purchased in various diameters. If you have a fax number I can see if I can find a picture of what I'm talking about.
Using this method you can achieve excellent results with a minimum of cost and problems.
Chuck Warner
Yuma Sprinkler and Pipe Supply
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