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

摘要

The different threshold crop water stress index (CWSI) values were determined and used as basis of the scheduling of irrigation for sunflower (H. annuus cv. Sunbro) grown under furrow irrigation in Tekirdag, Turkey, during the summer of 2003. Irrigation was started when the CWSI values reached 0.2, 0.4, 0.6, 0.8 and 1.0 (no irrigation). The CWSI values were computed based on measurements of canopy temperature, air temperature, and atmospheric vapour pressure deficit. The amount of irrigation water applied reached 679, 584, 470 and 227 mm for T0.2, T0.4, T0.6 and T0.8, respectively. The greatest seasonal evapotranspiration (809 mm) was measured from the T0.2 treatment. The irrigation levels significantly affected the seed yield. The highest seed yield (4.38 t ha-1) was obtained with T0.2, although this treatment was on a par with T0.4 and T0.6 in terms of seed yield. The results indicated that a CWSI value of 0.6 can be used for determining the appropriate irrigation time for sunflower under Tekirdag conditions..