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Use of a crop water stress index for scheduling the irrigation of sunflower (Helianthus annuus L.)

This study was designed to evaluate different threshold crop water stress index (CWSI) values to schedule irrigation for sunflower (Helianthus annuus L.) grown under furrow irrigation. | Turk J Agric For 30 (2006) 11-20 © TÜB‹TAK Use of a Crop Water Stress Index for Scheduling the Irrigation of Sunflower (Helianthus annuus L.) Tolga ERDEM*, Yeflim ERDEM, A. Halim ORTA, Hakan OKURSOY Faculty of Agriculture, Department of Farm Structures and Irrigation, University of Trakya, 59030 Tekirda¤ - TURKEY Received: 03.02.2005 Abstract: This study was designed to evaluate different threshold crop water stress index (CWSI) values to schedule irrigation for sunflower (Helianthus annuus L.) grown under furrow irrigation. Irrigations were started when CWSI values reached 0.2, 0.4, 0.6, 0.8 and 1.0 (non-irrigation). The CWSI values were computed from measurements of canopy temperature, air temperature and atmospheric vapor pressure deficit. Total irrigation water amounts of 679, 584, 470 and 227 mm were applied to the T0.2, T0.4, T0.6 and T0.8 treatments, respectively. The maximum seasonal evapotranspiration (ET), 809 mm was measured from the T0.2 treatment. Irrigation levels significantly affected seed yield. Although the highest seed yield (4.38 t ha-1) was obtained from the T0.2 treatment, the T0.4 and T0.6 treatments were not significantly different from the T0.2 treatment. Therefore, based on these results, a CWSI value of 0.6 can be used for the irrigation time of sunflower under Tekirda¤ conditions. Key Words: Crop water stress index (CWSI), infrared thermometer, furrow irrigation, evapotranspiration Bitki Su Stresi ‹ndeksi De¤erlerinin Ayçiçe¤inin Sulama Zaman› Planlanmas›nda Kullan›m› Özet: Bu çal›flma, kar›k sulama yöntemi ile sulanan ayçiçe¤inin sulama zaman›n›n planlanmas›nda farkl› bitki su stresi indeksi (CWSI) de¤erlerinin kullan›m olanaklar›n›n araflt›r›lmas› amac›yla yürütülmüfltür. Araflt›rmada, CWSI de¤erleri; yüzey s›cakl›¤›, hava s›cakl›¤›, buhar bas›nc› a盤› dikkate al›narak hesaplanm›fl ve sulamalara bu de¤er, 0.2, 0.4, 0.6, 0.8 ve 1.0’a (susuz) ulaflt›¤›nda bafllanm›flt›r. Araflt›rma sonucunda, toplam uygulanan sulama suyu .