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

Document Type : Research Paper

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Abstract

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= 3.5 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 S4scenarios. Also results
showed by increasing water salinity from 2.3 to 6.5 dS m-1, CWSI increased about three times.

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