Spray irrigation is a form of irrigation in which pressurized water is sprayed over plants to provide them with water. This type of irrigation is also sometimes called sprinkler irrigation, and it is very widely used all over the world. Many people think specifically of spray irrigation when they visualize an irrigation system, and irrigation systems of all sizes can be designed to work in this way, ranging from a home sprinkler to keep a lawn green to industrial sized sprinklers used to irrigate crops.
With a spray irrigation system, the irrigation sprinklers may be fixed in place, or located on movable frames. Some sprinkler heads will only spray in one direction, requiring careful placement, while others will rotate as they spray, delivering water across a broader area. Rotating heads are often preferred because it allows for the installation of a single sprinkler array to cover a big area.
Sources of water for spray irrigation vary. Some cities encourage the utilization of treated wastewater. This is an environmentally friendly choice which reduces the demand for fresh water, nourishes the plants, and reduces wastewater runoff into waterways. Treated wastewater can be used on ornamental crops and landscaping, but it may be banned for use on crops, depending on where in the world one is. Water for crops can come from wells, reservoirs, rivers, lakes, and streams.
The big disadvantage to spray irrigation is that it requires a lot of water. As the water is sprayed, some is blown away and some evaporates, requiring more water delivery to ensure that plants get enough water. Water may also flow faster than the soil can take it up, and because spray irrigation does not deliver precisely targeted jets of water, a great deal of water ends up nowhere near the plants being watered, which is wasteful. This is costly, and also environmentally unfriendly, as water may be diverted away from natural areas in need of water to feed the requirement for water supplies on farms.
An alternative method involves low pressure spray irrigation accomplished with hanging pipes. Instead of spraying water up and over, the pipes allow water to flow straight down. This requires less pressure and less water, conserving energy and water supplies. For even more efficiency, a drip irrigation system can be used, although such systems are expensive to install and maintain, which can become a major obstacle for gardeners and farms considering this alternative irrigation method.