What Is Pressurized Irrigation?

Basic Layout

• There are many variations of pressurized irrigation systems depending on the type of field, the crop and the kind of water delivery fittings needed, but the components of the basic system remain the same. They consist of the control station where the pressure is applied; the mains and submains, which are pipes of differing dimensions; the manifolds or feeder pipelines; and the laterals or irrigating pipelines equipped with emitters or other fixtures delivering water to plants.

Variations

• Pressurized irrigation systems range from sophisticated setups with high startup costs, like spray booms for forage and grains and center-pivot systems for agribusinesses. Moderate-cost systems include bubbler irrigation, mini-sprinklers for orchards and micro-sprinklers, which are low-capacity rotary sprinklers that give a rainfall effect for densely planted field crops. Examples of lower-cost systems are drip irrigation, which includes drip emitters, drip tape and porous-wall pipes, as well as the hand-moved hose basin system for trees, pipe distribution irrigation systems and hose-move sprinklers. Simple, inexpensive systems are called affordable micro-irrigation techniques, exemplified by family drip systems used for small landholdings in countries like China. Fertilizer injectors can be incorporated into pressurized irrigation systems to perform fertigation.

Advantages

• Pressurized irrigation systems avoid the water loss of open surface flow irrigation. Estimates indicate that open irrigation application efficiency is 45 percent to a maximum of 60 percent. In contrast, pressurized irrigation efficiency is 75 to 95 percent, according to a 2000 report by the Food and Agriculture Organization of the United Nations. To conserve water, many cities in the American West are turning to pressurized systems rather than surface flow irrigation to give homeowners irrigation water for yards. Pressurized irrigation allows the use of small bodies of water or runoff from rain that couldn't be used in traditional methods. It can also be tailored to expensive, complicated units like spray booms for agribusiness to simple, inexpensive systems like family drip systems for developing areas without electricity. Open canals have high maintenance requirements with skilled labor and large equipment needed. Pressurized irrigation systems need from one-tenth to one-quarter of the man hours open systems require, according to the same report by the Food and Agriculture Organization. In addition, pressurized irrigation systems can help increase food production and water conservation in developing countries where the need is high. Pressurized irrigation is especially valuable in arid and semi-arid areas.

Disadvantages

• Water quality is crucial to the prolonged operation of pressurized irrigation systems. Water high in dissolved minerals leads to frequent blocking of emitters. Routine maintenance is needed to unblock delivery fittings and to maintain pumps and fertigation units. Buildup of mineral salts in the soil around root zones may also cause problems with plant growth. Thus, water needs to be filtered before entering the irrigation system to remove suspended solids such as silt, algae, sand and dust, which will clog emitters. As many as three filters may be needed, and the filters need to be maintained rigorously.