By David A. Bainbridge
Associate Professor
United States International College of Business
Alliant International University
San Diego, CA 92131
http://www.ecocomposite.org/restoration/deeppipe.htm
Using a pipe, bamboo with the internal nodes punched out, or a bundle of straw or sticks to place irrigation water in the deep root zone is very effective and well suited for gardens, small farms, and remote landscaping and forestry projects. Deep pipe irrigation is commonly done with 1″ to 3″ diameter vertical pipe placed 12-18″ deep into the soil under or near the crop plant or tree. The top of the pipe should be covered with a cap or a screen disk. For large scale ecological restoration work we glue 1/8 inch galvanized screen disks to the top of the pipe with silicone caulk.
A series of small holes should be drilled in the side of the pipe near the plant if a seed is used or if a small transplant with roots shorter than the pipe is planted. The seed or seedling should be fairly close to the pipe (1-3 inches for a young plant). Several pipes are used for a full grown tree. These can be arranged to encourage root growth to resist windthrow and minimize interference with inter-planted crops.
These may be filled with water bottles placed in the pipe (observed in Kenya), filled with water from a water truck or hose, or fitted with a drip emitter. If a drip system can be setup the pipe can be smaller diameter (1/2″). We have set up a deep pipe irrigation system on a remote tank with battery powered timer to irrigate once a week with excellent success.
Deep pipe irrigation is better than surface or buried drip systems in several respects. First, it can be used with low quality water and low technology. Second, even in areas where the materials and technology for drip systems are available the deep pipe system provides the benefits of buried drip, greater water use efficiency (due to reduced evaporation) and weed control; but the surface mounted deep delivery drip systems can be monitored and repaired much more easily. And, finally, the pipes can be collected at the end of the season for full field tillage operations to any depth desired.
Experiments in Africa and San Diego county have demonstrated that deep pipe systems are much more efficient than surface drip or conventional surface irrigation. Deep pipe irrigation develops a much larger effective rooting volume and plants better adapted to survive on their own. Survival of trees on deep pipes in the California desert has been excellent after modest irrigation (a total of a few gallons over the first two years) compared to total failure of surface irrigated trees given the same amount of water. After five years tree survival was excellent, and some trees were 15 feet tall.
Deep pipe irrigation can be especially useful on slopes and in crusty soils where surface applied water will run off. It increases the ease of watering remote sites and has been very effective in land restoration projects. It should be much more widely used!
Further Reading:
Bainbridge, D.A., M. Fidelibus and R. MacAller. 1995. Techniques for plant
establishment in arid ecosystems. Restoration and Management Notes
13(2):198-202
Bainbridge, D.A., Robert MacAller, M. Fidelibus, R. Franson, L. Lippitt, and A.C.
Williams. 1995. A Beginners Guide to Desert Restoration. National Park Service,
Denver, CO 34 pages.
Sawaf, H.M. 1980. Attempts to improve the supplementary irrigation systems in
orchards in some arid zones according to the root distribution patterns of fruit
trees. In: Rainfed Agriculture in the Near East and North Africa. FAO, Rome,
Italy pp. 252-259
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