Irrigation may be defined as the science

Science

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...

 of artificial application of water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 to the land or soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. It is used to assist in the growing of agricultural crops

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, maintenance of landscape

Landscape

Landscape comprises the visible features of an area of land, including the physical elements of landforms such as mountains, hills, water bodies such as rivers, lakes, ponds and the sea, living elements of land cover including indigenous vegetation, human elements including different forms of...

s, and revegetation

Revegetation

Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, or an artificial , accelerated process designed to repair damage to a landscape due to wildfire, mining, flood, or other cause...

 of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost,
suppressing weed growing in grain fields and helping in preventing soil consolidation.
In contrast, agriculture

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 that relies only on direct rainfall is referred to as rain-fed or dryland farming

Dryland farming

Dryland farming is an agricultural technique for non-irrigated cultivation of drylands.-Locations:Dryland farming is used in the Great Plains, the Palouse plateau of Eastern Washington, and other arid regions of North America, the Middle East and in other grain growing regions such as the steppes...

.