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Enhancing Water Use Efficiency in Irrigated Agriculture

USDA-ARS, Conserv. and Production Res. Lab., P.O. Drawer 10, Bushland, TX 79012

Corresponding author (tahowell{at}cprl.ars.usda.gov)

Irrigated agriculture is a vital component of total agriculture and supplies many of the fruits, vegetables, and cereal foods consumed by humans; the grains fed to animals that are used as human food; and the feed to sustain animals for work in many parts of the world. Irrigation worldwide was practiced on about 263 Mha in 1996, and about 49% of the world's irrigation occurred in India, China, and the USA. The objectives of this paper are to (i) review irrigation worldwide in its ability to meet our growing needs for food production, (ii) review irrigation trends in the USA, (iii) discuss various concepts that define water use efficiency (WUE) in irrigated agriculture from both engineering and agronomic viewpoints, and (iv) discuss the impacts of enhanced WUE on water conservation. Scarcely one-third of our rainfall, surface water, or ground water is used to produce plants that are useful to mankind. Without appropriate management, irrigated agriculture can be detrimental to the environment and endanger sustainability. Irrigated agriculture is facing growing competition for low-cost, high-quality water. In irrigated agriculture, WUE is broader in scope than most agronomic applications and must be considered on a watershed, basin, irrigation district, or catchment scale. The main pathways for enhancing WUE in irrigated agriculture are to increase the output per unit of water (engineering and agronomic management aspects), reduce losses of water to unusable sinks, reduce water degradation (environmental aspects), and reallocate water to higher priority uses (societal aspects).

Abbreviations: ET, evapotranspiration • ET_d, evapotranspiration for an equivalent dryland or rainfed only plot • ET_i, evapotranspiration for irrigation level i • ET_WUE, evapotranspiration water use efficiency • FAO, Food and Agriculture Organization • I_WUE, irrigation water use efficiency • LEPA, low-energy precision application • P, precipitation • WUE, water use efficiency • Y_d, yield for an equivalent dryland or rainfed only plot • Y_i, yield for irrigation level i

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