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Why do some agricultural lands need irrigation before crops can be grown?

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Large wheeled irrigation sprinkler sprays water over green crops in a field, with mountains and cloudy sky in the background. — Irrigation Specialized irrigation equipment watering crops in a field.

Agricultural lands require irrigation primarily to provide the necessary moisture for crop growth when natural precipitation is insufficient or unreliable. Some land is naturally arid or semi-arid, meaning it lacks the rainfall required for agricultural production and must be reclaimed through the artificial application of water to become productive.123

In other regions, irrigation is used to supplement rainfall, particularly during extended dry periods or seasons where precipitation is inadequate to meet the specific water needs of crops. Because different crops have varying water requirements—for example, rice often requires significantly more water than cereal grains—irrigation ensures that soil moisture remains sufficient throughout the growing season. Without this consistent water supply, agricultural production in these areas would face high risks of crop failure due to agricultural drought, which occurs when there is insufficient soil moisture to support plant development.21456