ORIGINAL PAPER Consumptive water use and crop coefficients of irrigated sunflower R. Lo ´pez-Urrea • A. Montoro • T. J. Trout Received: 21 March 2013 / Accepted: 16 September 2013 / Published online: 4 October 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract In semi-arid environments, the use of irrigation is necessary for sunflower production to reach its maximum potential. The aim of this study was to quantify the con- sumptive water use and crop coefficients of irrigated sun- flower (Helianthus annuus L.) without soil water limitations during two growing seasons. The experimental work was conducted in the lysimeter facilities located in Albacete (Central Spain). A weighing lysimeter with an overall resolution of 250 g was used to measure the daily sunflower evapotranspiration throughout the growing sea- son under sprinkler irrigation. The lysimeter container was 2.3 m 9 2.7 m 9 1.7 m deep, with an approximate total weight of 14.5 Mg. Daily ET c values were calculated as the difference between lysimeter mass losses and lysimeter mass gains divided by the lysimeter area. In the lysimeter, sprinkler irrigation was applied to replace cumulative ET c , thus maintaining non-limiting soil water conditions. Sea- sonal lysimeter ET c was 619 mm in 2009 and 576 mm in 2011. The higher ET c value in 2009 was due to earlier planting and a longer growing season with the maximum cover coinciding with the maximum ET o period. For the two study years, maximum average K c values reached values of approximately 1.10 and 1.20, respectively, during mid-season stage and coincided with maximum ground cover values of 75 and 88 %, respectively. The dual crop coefficient approach was used to separate crop transpira- tion (K cb ) from soil evaporation (K e ). As the crop canopy expanded, K cb values increased while the K e values decreased. The seasonal evaporation component was esti- mated to be about 25 % of ET c . Linear relationships were found between the lysimeter K cb and the canopy ground cover (f c ) for the each season, and a single relationship that related K cb to growing degree-days was established allowing extrapolation of our results to other environments. Introduction Sunflower (Helianthus annuus L.) is one of the most important oil crops worldwide (S ˇ koric ´ 1992), and among oil crops, it is the fifth most cultivated annual crop. The sunflower global planted area was 26 million ha in 2011, with a production of 40.2 million Mg. In the European Union (EU), more than 4 million ha were cultivated in 2011 with a production of 8.3 million Mg, approximately 21 % of the world production. In Spain, the sunflower cultivated area has increased in the recent years from 516,000 ha in 2005 to nearly 860,000 ha in 2011 (FAO- STAT 2011). Sunflower is cultivated in several Spanish regions to produce oil, to feed livestock and to produce biodiesel. Recently, the latter use is increasing. Drought- tolerant energy crops are seen as promising cropping alternatives in semi-arid areas, given their capacity of adaptation to dry climatic conditions. Only about 10 % of the total area of sunflower culti- vated in Spain is irrigated, although irrigation often results in yield increases of over 100 % (MAGRAMA 2010). In other semi-arid areas, such as Turkey, Lebanon, Kansas (USA) and Texas (USA), irrigation of sunflower has Communicated by S. Ortega-Farias. R. Lo ´pez-Urrea (&)  A. Montoro Instituto Te ´cnico Agrono ´mico Provincial (ITAP) and FUNDESCAM, Avda. Gregorio Arcos 19, 02005 Albacete, Spain e-mail: rlu.itap@dipualba.es T. J. Trout USDA-ARS, Water Management Research Unit, 2150 Centre Avenue, Building D, Fort Collins, CO 80526-8119, USA 123 Irrig Sci (2014) 32:99–109 DOI 10.1007/s00271-013-0418-9