Investigation of the Effect of Water Irrigation Salinity on The Performance of CWSI Index Under The Climatic Conditions of Ahvaz

Irrigation scheduling under water and salinity stress, is much more difficult than full irrigation scheduling. To investigate the effect of plant water stress, there are many indicators. One of them is crop water stress index (Idso method). To evaluate the ability of this index for irrigation scheduling of summer Maize (SC704 variety) and winter Maize (Mobin variety)- in conditions of using saline water, a research was designed at the research station of Shahid Chamran University in 2013-2014 . This research consisted of five quality treatments of irrigation water, including S0: Water Caron, S1: EC= 3.5dS / m, S2: EC=4.5dS / m, S3: EC=5.5dS / m and S4: EC=6.5 dS / m. In the both of the growing seasons, result showed, The upper and lower base lines were affected by salinity stress. The amount of upper and lower base lines for summer Maize were higher than the winter Maize. The lower and upper baseline's equation for summer Maize were (Tc-Ta)l.l=1.641-0.178VPD and h=2.52 0c and for winter Maize were (Tc-Ta)l.l=2.161-0.221VPD and h=3.69 0c. CWSI, which is the base of irrigation scheduling, was calculated 0.23 for summer Maize and 0.17 for winter Maize. By increasing water salinity from 2.2 to 6.5 ds/m, the temperature difference between canopy cover and air was 30C for summer maize and 20C for winter Maize. At this research CWSI was calculated on the days, before irrigation for all treatments and result showed that in the both of seasons, CWSI was increased about three times when water salinity increased from 2.2 to 6.5 dS/m. The effect of salinity stress was calculated separately according to the days, after irrigation (at These days, the effect of salinity is sensible). results showed that CWSI increased about 3.5 times for summer Maize and around 3 times for winter Maize when water salinity increased from 2.2 to 6.5 dS/m. Comparing the results of the two seasons showed that CWSI is affected by irrigation water salinity and it's trend was nearly the same in both of the growing seasons.