Comparison of Water-Yield Relations, Water Deficit Index, and Crop Water Stress Index in Silage Maize (Zea mays L.) and Sorghum (Sorghum bicolor L.)

In this study, water-yield relations, Crop Water Stress Index (CWSI), which is one of the commonly used crops stress indicators, and the Water Deficit Index (WDI), which is a new approach, were compared by applying deficit irrigation in ۲۰۱۸-۲۰۱۹ growing period in Kahramanmaraş, Turkey. Five irrigation levels were applied to silage maize and sorghum plants. According to the results, yield was higher in silage maize than in silage sorghum both in full irrigation (۱۰۰%) and in water-deficit irrigation (treatment where ۸۰%, ۶۰%, ۴۰%, ۲۰% meeting water requirement of plant). However, when average yield values of both years were examined, maize showed a decrease of ۴۹ and ۴۶%, respectively, while sorghum showed a decrease of ۳۳%, compared to treatment with ۴۰ and ۲۰% irrigation, respectively. Similarly, there was a decrease of ۶۶-۵۴% in maize for ۲۰% treatment, while there was a decrease of ۴۵-۴۶% in sorghum. This showed that sorghum maintained its yield potential better than maize in conditions of ۶۰% or more water constraint. When the average CWSI and WDI indices were examined mutually, it was observed that rate of increase in stress and amount of decrease in productivity gave more consistent results in WDI than in CWSI. It has been understood that CWSI, one of crop stress determiners, is insufficient in determining stress compared to WDI, and WDI gives more accurate results. Accordingly, complete and accurate results of WDI have been obtained despite the shortcomings of CWSI method, which has been used in stress determination until now. It is suggested to use WDI for crop water stress index.

Keywords:

Evapotranspiration , Irrigation , Crop canopy , Water scarcity.