Determination of A Crop Water Stress Index (CWSI) For Detecting Water Stress time of Maize Crop in the Urmia Region

Infrared thermometer is one of the proper irrigation scheduling tools that can be used in fields or gardens with different soil texture. In order to schedule irrigation of maize (SC704) in Urmia climate conditions, using a difference in temperature of canopy cover of plant and air in 2017, a research was conducted at research farm of Urmia University college of agriculture under drip irrigation. In this research, the effects of various irrigation water treatments were investigated. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 of 50, 75 and 100 percent of water requirement in three replications, respectively. Based on the results, the average values of CWSI for maize during the growth period for treatments of I1, I2 and I3 were calculated to be 0.53, 0.44 and 0.28, respectively. The results showed that the CWSI index increased with decreasing water requirement. The threshold of water stress index (0.28) of I3 treatment (no stress treatment) was the basis for irrigation scheduling. Then, some relationships were presented to determine the irrigation time of maize, using the CWSI index in Urmia climate for July, August and September as ,and  respectively.