Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Sunflower (Helianthus annuus L.) is a diverse crop grown for oil or confectionary uses in the Southern High Plains often under irrigation. Crop water use (evapotranspiration or ET) was measured in 2009 and 2011 in two 4-ha fields using two precision 9 m2 weighing lysimeters containing 2.3-m deep monoliths of Pullman clay loam soil. The fields were irrigated with a lateral move sprinkler system with nozzles ~1.7-1.8 m above the ground and ~1.5-m apart. The sunflower ET averaged 638 mm; seed yields averaged 308 g m-2; and the lysimeter water productivity averaged 0.49 kg m-3. The crop coefficients based on the FAO-56 curve method were 0.15 for Kcbini and 1.22 for Kcbmid based on the daily ASCE Reference ET (ETos). The Kcbmid based on the ASCE taller, rougher Reference ET (ETrs) was 0.80. Using a thermal-time base (growing degree day) for the crop coefficient did not improve the crop coefficient for the diverse planting dates in these seasons.