Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 2000
Publication Date: N/A
Interpretive Summary: Irrigation is the principal method for increasing crop yields in regions where precipitation is inadequate or too erratic to meet the crop needs. Irrigation requires large quantities of high quality water. The purpose of this paper was to review irrigation from a world level, from the United States' level, and to discuss methods for improving the crop yield per unit tof water used in irrigated agriculture. In the world, about 650 million acres (about 15% of the cultivated land) produces about 36% of the world's food. In the U.S., irrigated lands have increased by 5.65 million acres from 1992 to 1997 and total about 50 million acres. In addition, significant changes have occurred in the irrigation technology with a shift to center pivots and drip and a decline in surface irrigation. Water use efficiency (WUE) is defined as the crop yield per unit of water use. Agronomy and engineering are the predominate means for enhancing WUE. But WUE can be increased by reducing losses of water to unusable water source with degraded quality and by reallocating water to its highest use. The last item is strongly linked to societal aspects affecting water use and regulations.
Technical Abstract: Irrigated agriculture is a vital component of total agriculture and supplies many of the fruits, vegetables, and cereal foods used by humans; the grains fed to animals that are used as human food; and the feed to sustain animals in many parts of the world. World-wide irrigation was used on about 263 million ha in 1996 with about 49% of the world's irrigation in nIndia, China, and the United States. The objective of this paper is to review the importance of irrigation to agricultural production in the world and in the United States and to examine mechanisms to enhance water use efficiency (WUE) in irrigated agriculture. Frequent reports indicate that scarcely one-third of our rainfall, surface water, or groundwater is used to produce useful plants. Without careful management, irrigated agriculture has been detrimental to the environment and has endangered sustainability. Irrigated agriculture is facing growing competition for low-cost, high-quality water. WUE in irrigated agriculture is broader in scope than most agronomic applications and must be considered on a basin or catchment scale. The main pathways for enhancing WUE in irrigated agriculture are to increase the output per unit of water (engineering and agronomic aspects), reduce losses of water to unusable sinks and reduce water degradation (environmental aspects), and reallocate water to higher uses (societal aspects).