Determination of crop water stress index and irrigation scheduling of cotton by using infrared thermometer techniques in Aydin plain conditions

The study has been conducted in the fields of the Research and Application Farm of Faculty of Agriculture at Aydın Adnan Menderes University, during the year of 2018. This study was carried out to determine crop water stress index (CWSI) to predict raw cotton yield under Aydın province. The effects of five different irrigation levels (100, 75, 50, 25 and 0 % replenishment of soil water depleted from the 1.20 m soil profile depth) on raw cotton yields and the resulting CWSI were investigated. The highest yield and total water use were obtained under fully irrigated cotton plots (100 % replenishment of soil water depleted). The raw cotton yield, water use and water use efficiency of fully irrigated cotton were 598,5 kg/da, 801 mm, and 0,747 kg/m3, respectively. The CWSI was calculated from measurements of canopy (Tc) and ambient air (Ta) temperatures and vapor pressure deficit (VPD) values for five irrigation levels. The CWSI values increased with increased soil water deficit and raw cotton yields decreased with increasing CWSI values. The results of this study indicated that the CWSI values could be useful to determine irrigation time. An average CWSI of 0.22 before irrigation time provided highest raw cotton yield from S1 fully irrigated treatment. The yield was directly correlated with seasonal mean CWSI values and the second order polynomial equation "Y = -2161,8 CWSI2 + 1007,5 CWSI +511,76"can be used to predict the yield potential of raw cotton under the Aydın province.