Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 19, 1997
Publication Date: N/A
Technical Abstract: Evapotranspiration (ET) from well-watered alfalfa with no limitations to growth is one of two common reference ET values used to scale ET from other crops to obtain crop coefficient (Kc) values for irrigation scheduling - the other is grass reference ET. Alfalfa (Medicago sativa, var. Pioneer 5454) was seeded at 28 kg/ha in September 1995 and grown in 1996 and 1997 on Pullman clay loam (Torrertic Paleustoll) at Bushland, TX. The crop was well-watered with a lateral move sprinkler. Monolithic weighing lysimeters (3 m by 3 m in surface area and 2.4 m deep) measured ET every half hour to 0.05 mm precision. In 1996, yield was 16.5 dry t/ha from 4 cuttings; and, crop water use exceeded 915 mm. Daily ET in this windy, semi-arid environment exceeded 14 mm on occasion. Alfalfa reference ET will be compared with grass reference ET from a nearby separate experiment (see Howell and Evett in this publication). Alfalfa reference ET will also be compared with ASCE and FAO versions of the Penman-Monteith equation for theoretical alfalfa reference ET.