Location: Water Management and Systems ResearchTitle: Consumptive Water Use and Crop Coefficients of Irrigated Sunflower Author
Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2013
Publication Date: 8/1/2013
Citation: Lopez-Urrea, R., Montoro, A., Trout, T.J. 2013. Consumptive Water Use and Crop Coefficients of Irrigated Sunflower. Irrigation Science. 32:99-109. DOI 10.1007/s00271-013-0418-9. Interpretive Summary: Sunflower, a major crop in many semi-arid parts of the world, is grown for food, oil, and biofuels. Although somewhat drought tolerant, sunflower is sometimes irrigated to increase yields. Crop coefficient parameters are needed to efficiently schedule irrigation applications to sunflower. In this study, water requirements and crop coefficients were determined for sunflowers in a weighing lysimeters study in Albacete, Spain. The study found that sunflower uses about 600 mm of water, and the water use depends upon whether the crop is planted early or late in the spring. The peak crop coefficient for sunflower is about 1.15 or 15% higher than for a grass reference crop. With this information, growers can use reference evapotranspiration information from weather station networks to efficiently schedule irrigation applications.
Technical 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 consumptive water use and crop coefficients of irrigated sunflower (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 seasonal sunflower ET under sprinkler irrigation. The lysimeter container was 2.3 m x 2.7 m and 1.7 m deep, with an approximate total weight of 14.5 Mg. To schedule irrigation, daily ETc 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 ET, thus, maintaining non-limiting soil water conditions. Seasonal lysimeter ETc was 619 mm in 2009 and 576 mm in 2011. The higher ETc value in 2009 was due to a longer growing season and the maximum cover coinciding with the maximum ETo period (early planting). For the two study years, maximum average Kc values reached values of approximately 1.10 and 1.20, respectively during mid-season stage and were related to maximum ground cover values of 75 and 88 percent, respectively. The dual crop coefficient approach was used to separate crop transpiration (Kcb) from soil evaporation (Ke). As the crop canopy expanded, Kcb values increased while the Ke values decreased. The seasonal evaporation component amounted to about 25% of ETc. Linear relationships were found between the lysimeter Kcb and the ground cover (fc) for the two seasons, and a single relationship that related Kcb to growing degree-days (GDD) was established allowing extrapolation of our results to other environments.