Determination of threshold values of leaf water potential (LWP) as an indicator of irrigation scheduling for cotton in Aydın plain conditions

Objective: This study was carried out to determine irrigation time of the Sahra cotton cultivar by using LWP method under Aydın plain conditions. Material and Methods: This study was conducted in year 2023 at the Research and Application Farm of the Agriculture Faculty of Aydın Adnan Menderes University by using the Sahra cotton cultivar. The trial was designated in randomized complete block design with three replications. The trial involved four different irrigation levels (100%, 67%, 33%, and 0%—rainfed), applied in three replications. In the trials, irrigation water was applied to treatments using drip irrigation method as 100%, 67%, 33% and 0% of evaporation from Class A Pan corresponding to 7-day irrigation interval. In this study, variation of leaf water potential (LWP) has been checked in water potential versus to time of cotton plant at different irrigation treatments. Results: The applied irrigation levels to different treatments significantly affected seed cotton yield and fiber quality parameters. Seasonal plant water consumption ranged from 374,4 to 703,4 mm. The average seed cotton yield ranged between 168,5 and 506,0 kg/da. The highest yield was obtained from the fully irrigated treatment (100%-Sahra) at 506,0 kg/da. LWP results were given as follows to all treatments before irrigation aplications 100 % treatment as LWP = -19,0 bar; 67 % treatment as LWP = -19,8 bar; 33 % treatment as LWP = -22,8 bar and 0 % treatment as LWP = -26,8 bar respectively. The seasonal water use was directly correlated with seasonal mean LWP values and the linear relation was determined. Conclusion: The highest yield has been obtained at 100 % treatment according to these results. The results of this study indicated that the LWP values could be useful to determine irrigation time. An average LWP of -19,0 bar before irrigation time provided highest seed cotton yield from 100 % fully irrigated treatment. It may be concluded that the treatment which gave the best performance was treatment S100 when the water was abundant. In the case of water scarcity S67 (deficit irrigation) treatments resulted in reasonable yield, WUE and fibre quality. Key Words: Aydın, Deficit irrigation, Cotton, Leaf water potential (LWP).