Measuring Crop Water Requirement and Crop Coefficient for Blue Panic Crop Under Arid Conditions Using Draining Lysimeters

Previous research results of Blue Panic ( Panicum antidotale Retz) in arid conditions under different irrigation methods proved an increase in forage yield and water productivity (WP) under full and water stress conditions. However, a thorough search in the literature revealed that its water requirement has not yet been determined. Therefore the objective of this research was to measure evapotranspiration (ET c ) and crop coefficient ( K c ) for a Blue Panic crop under arid conditions. Four draining lysimeters constructed in Jeddah (21° 48′ 3′′ N, 39° 43′ 25′′ E) were used to measure its ET c and K c under a plentiful water supply. Results revealed that ET c varied from 141 mm in the first harvest to 292 mm in the sixth, with an average of 225 mm per harvest. The K c value was different from one harvest to another. The average K c over all harvests was 0.7, 1.2, 1.3 and 1.0 for the initial, development, midseason and late stages, respectively. Average fresh and dry forage yields per harvest were 30.5 and 12.6 t ha −1 , respectively. Average WP was 55 kg ha −1 mm −1 . The predicted ET c based on the measured crop coefficient value and ET 0 show a good fit between measured and calculated ET c . Copyright © 2018 John Wiley & Sons, Ltd.