Monday, 7 November 2005
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This presentation is part of: Evapotranspiration

Nighttime Evapotranspiration from Alfalfa and Cotton in a Semiarid Environment.

Judy Tolk, Steven R. Evett, and Terry A. Howell.

Nighttime evapotranspiration (ETn) has typically been neglected in estimating water loss from land surfaces. Our objective was to quantify the contribution of ETn to daily (24-h) ET24 of irrigated and dryland cotton (Gossypium hirsutum L.) and irrigated alfalfa (Medicago sativa L.) grown in a semiarid climate. Nighttime ET was measured at Bushland, TX using weighing lysimeters containing monolithic soil cores of a clay loam soil for alfalfa in 1998 and cotton in 2001. The ETn of alfalfa averaged 6.9 % of ET24, with losses exceeding 1 mm occurring on at least 10 nights, with a maximum single night loss of 1.94 mm. Average ETn of cotton contributed from 3 % under dryland conditions to 7 % under fully irrigated conditions. The largest single ETn event for cotton was 1.24 mm, with events exceeding 1 mm occurring four times. Nighttime ET can be an important part of total daily ET of irrigated drops in a semiarid environment.

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