Applicability of CWSI Index for Irrigation Scheduling of Maize Using Saline Water in Ahvaz

Irrigation scheduling under water and salinity stresses is more difficult than normal conditions. To investigate the effect of water stress on crop growth, numerous indices have been introduced which one of them is crop water stress index (CWSI). To evaluate the suitability of this index for irrigation scheduling of corn (maize) with using saline water, a field experiment consisted of irrigation water with five salinity levels (S0: Caroon River (EC= 2.3 dS m-1), S1: EC= . dS m-1, S2: EC=4.5 dS m-1, S3: EC=5.5 dS m-1 and S4: EC=6.5 dS m-1) was conducted at the research station of Shahid Chamran University, Iran. Results showed that the lower baseline equation (without stress) for the summer corn was (Tc-Ta)ll=2.161-0.221 VPD and the upper baseline equation (with full stress) was h=3.690C. The CWSI value as a base for irrigation scheduling was calculated to be 0.23. Also it was found that increasing water salinity caused to increase the foliage temperature. Thus, CWSI may be used for irrigation scheduling under conditions of using saline water. By increasing water salinity from 2.2 to 6.5 dS m-1, the temperature difference between the canopy and air was increased by 30C, approximately. In this research, CWSI values at the day just before the irrigation were 0.23 for S0, 0.35 for S1, 0.46 for S2, 0.58 for S3 and 0.73 for S scenarios. Also results showed by increasing water salinity from 2.3 to 6.5 dS m-1, CWSI increased about three times.