Corn grain irrigation programming using CWSI index in Ahwaz climatic conditions

The use of green cover temperature for plant irrigation planning is one of the methods that has been considered by researchers. For this purpose, several indicators have been presented, among which we can mention the water stress index of the plant by Idso method. In order to plan summer corn irrigation in climatic conditions of Ahvaz using green cover temperature, in 2018 research in the research farm of Shahid Chamran University of Ahvaz Faculty of Water Engineering under four types of irrigation regime including I0, I1, I2 and I3 respectively 120 , 100, 80 and 60% of the plant's water requirement was done in a completely randomized design in three replications. Based on the results, the equation of the upper and lower base line for the corn plant, treatment I1 (100% water requirement) for the development stage is 2.89 and (Tc-Ta) ll = 1.984-0.0946VPD, for the middle stage is 3.4 and (Tc-Ta) ll = 3.217-0.1669VPD and for the final stage of growth was equal to 1.2 and (Tc-Ta) ll = 1.147-0.160VPD was obtained in degrees Celsius. The results also showed that the total water stress index for the growth period for the 120, 100, 80 and 60 treatments was 0.17, 0.22, 0.35 and 0.52, respectively. The relationship between plant water stress index and soil moisture level for different irrigation treatments was highly correlated and the equation of soil stress index with soil moisture for I1 treatment for the next day and before irrigation was equal to CWSI = 1.8296-0.0586ɵv and CWSI = 1.038 0.0281ɵv was obtained. The results showed that with decreasing water consumption, the plant's water stress index increased and with increasing water stress, the correlation between CWSI index and soil water depth decreased so that the highest R2 (0.97) in I0 treatment and the lowest R2 (0.88) was in I2 and I3 treatments. As the results of this study confirm, the plant's water stress index is a good tool for irrigation planning and optimal management in the field.