Uçak, Ali BeyhanSeçme, Halis2024-12-242024-12-2420212148-127Xhttps://doi.org/10.24925/turjaf.v9i12.2289-2295.4641https://search.trdizin.gov.tr/tr/yayin/detay/511421https://hdl.handle.net/20.500.12604/4564This study was carried out in 2020 to determine crop water stress index (CWSI) by using infrared\rthermometer (IRT) data calculated by leaf canopy temperature measurements of the second crop\rsunflower genotype in semi-arid climate conditions, and to determine the relationships between\rirrigation time, seed yield of sunflower plant and CWSI by using these index values. Irrigation\rprogram consisted of a full irrigation and 2 different levels of stress, which were 100% (I100), 70%\r(I70), 35% (I35) of water losses within the effective root depth of 90 cm every 7 days. A total of\r644 mm of irrigation water was applied to I100 (control) irrigation. The water consumption for full\rirrigation was 721 mm and the yield was 3516.00 kg/ha. Lower limit (LL) value without water\rstress required to determine plant water stress index was Tc-Ta=-2.528×VPD +0.749 (R2=0.814)\rand upper limit (UL) value, where the plant is completely under water stress, was determined as\r+3.27°C. Crop water stress index value threshold at which sunflower seed yield started to decrease\rwas calculated as 0.33 using the infrared thermometer measurements at the time of irrigation. In\raddition, a negative correlation was obtained between sunflower seed yield and CWSI values. The\rresults revealed that the yield tends to decrease as the CWSI increaseseninfo:eu-repo/semantics/openAccessZiraat MühendisliğiArticle9122289229551142110.24925/turjaf.v9i12.2289-2295.4641