Drip irrigation System Design

Drip or trickle irrigation is the latest development in irrigation system design. Small amounts of water are allowed to trickle slowly into the soil through mechanical devices called emitters, wetting the soil without runoff. The emission rate of water ranges from about 2 to 9 liter per hr (0.5 to 2 gal/hr). Emitters are connected to a small plastic lateral tube, laid either on the soil surface or buried just beneath it for protection. Some drip irrigation systems have the emitters built into the lateral line or tube. The lateral lines are connected to a buried main line that receives water from a head source. The head source is the control station for the system. Here the water is filtered, may be treated with fertilizers, and is regulated for pressure and timing of application.

Some advantages of drip irrigation are:

1. the system need not be moved;
2. there is little interference with orchard cultural operations because much of the soil surface is not wetted;
3. there is less fluctuation of soil moisture in the root zone area because of the constant and slow drip application of water, and
4. less water is needed to grow a crop.

The area of wetted soil can be as little as 10 percent of the total area of newly planted tree crops or up to 60 percent of the area of a mature crop. The amount of soil wetted depends on the soil’s physical properties, the time of application, and the number of emitters used. Some objections are

1. expensive filtration equipment is needed to avoid frequently clogged emitters;
2. water distribution may be uneven hilly land;
3. salts tend to concentrate on the soil surface and near the wetted area boundary, and because leaching with excess water does not occur; and
4. the distribution of roots may be restricted to the small volume of wetted soil.

Drip irrigation may not fit the needs of every crop or situation, but its use by orchardists, strawberry growers, or namental nurseries, and for some high-yield field crops is rapidly increasing.

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