The goal of all irrigation methods is to make plants thrive. There is actually a science to growing fruits, vegetables and plants; it's called horticulture. Growing plants can either be a personal hobby or a commercial enterprise, but certain basic tenets apply to all types of plant-growing activities.
Overhead irrigation is commonly used on large tracts of land. It's even possible to take apart certain overhead systems and move them from one part of the field to the next. All overhead irrigation methods operate in basically the same way. The principle behind the overhead irrigation system is similar to that of a lawn sprinkler; spray nozzles pump out water that is under pressure onto the plants below. These nozzles are located on a series of aluminum pipes that hover over the field. Sometimes, simple stakes are used instead of aluminum pipes.
One challenge for an overhead irrigation system is even coverage. As such, more elaborate systems include an overhead boom that is mobile enough to reach the entire field and is therefore able to water the crops more evenly. Another device that can be part of an overhead irrigation system is the water gun. Unlike the moving overhead boom, the water gun remains stationary. However, since some water guns have a range of up to several acres, moving them from place to place isn't as critical.
All overhead irrigation systems need large amounts of pressurized water to function properly. As such, the complexity and cost of different irrigation systems tend to vary widely depending on the size of the land tract that is being covered. Another important, less-positive feature of the overhead irrigation system is that it wets crop foliage in the process of watering a field. As a result, bacterial disease and fungi problems could arise if leaves remain wet for a prolonged period of time -- anywhere from 10 to 24 hours.