Irrigation, applying water to assure sufficient soil moisture is available for good plant growth, as practiced in North Dakota is called "supplemental irrigation" because it is used to augment the rainfall that occurs during the growing season. Irrigation is used on full season agronomic crops to provide a dependable yield every year. It is also used on crops where water stress affects the quality of the yield, such as flowers, vegetables and fruits.
During most years it is not uncommon for some places in the state to receive sufficient rainfall for good plant growth while other areas experience reduced yields or quality on non-irrigated crops because of water stress from insufficient soil moisture. For irrigation planning purposes, average precipitation during the growing season is not a good yardstick for determining a need for irrigation. The timing and amounts of rainfall during the season, the soil's ability to hold water, and the crop's water requirements are all factors which influence the need for irrigation. Any location in the state can have what might be considered "wet" or "dry" weeks, months and even years.
Under irrigation, soil and water compatibility is very important. If they are not compatible, the applied irrigation water could have an adverse effect on the chemical and physical properties of the soil. Determining the suitability of land for irrigation requires a thorough evaluation of the soil properties, the topography of the land within the field and the quality of water to be used for irrigation. A basic understanding of soil/water/plant interactions will help irrigators efficiently manage their crops, soils, irrigation systems and water supplies.