Determination of Irrigation Time by Utilizing Plant Water Stress Index (CWSI) Values of II. Crop Sesame Genotype in Siirt Conditions

Abstract— This research was carried out to determine the plant water stress index (CWSI) by using infrared thermometer (IRT) data calculated as a result of leaf crown temperature measurements of the second crop sesame plant grown in semi-arid climate conditions in Siirt, and to determine the relationships between irrigation time and seed yield of sesame plant and CWSI by using these index values. In this study, the irrigation program was established to reintroduce 100 % (I₁₀₀), 70% (I₇₀), %35 (I₃₅) of the decreased water through the effective root depth of 90 cm every 7 days. Thus, a full irrigation (I₁₀₀) and irrigation with 2 different levels of stress (I₇₀ and I₃₅) were created. In the research, a total of 575.00 and 576.66 mm of irrigation water was given to I100 (control) irrigation in the first and following years, respectively. The water consumption of the above-mentioned subject was determined as 606.00 mm in the first year and 646.33 mm in the second year of the study. The yield per hectare in the first year of the research on the aforementioned irrigation was 1110.34 kg; In its second year, it was determined as 1319.00 kg. In the first and second years of the study, the lower limit (LL) values for the absence of water stress needed to determine the plant water stress index were Tc-Ta=0.373-2.42 VPD and Tc-Ta=0.74-2.52 VPD, respectively; The upper limit (UL) values, where the plant is completely water stressed, were determined as 2.04 °C and 1.77 °C, respectively. From the infrared thermometer measurements at the time of irrigation, the threshold plant water stress index value, where sesame seed yield starts to decrease, was calculated as 0.31. On the other hand, it was determined that there is a negative linear proportionality between sesame seed yield and plant water stress index values.