Modeling the Amount of Soil Moisture using Crop Water Stress Index (CWSI) in Maize Planting

In order to estimate the amount of soil moisture by the Crop Water Stress Index (CWSI), research was performed on the maize (SC 704). The experiment was a factorial and in format of randomized complete block design. In the control, treatment was done full irrigation and in other treatments, was applied water stress in the stages of 6-leaf, 12-leaf, flowering and seeds milking. The meteorological parameters, stomata resistance and leaf surface temperature were measured daily. At different growth stages, the stress low line had a slope of 0.09 to 0.14. The amount of the stress up line was estimated between 3.3 and 4.2 . In the period of stress, the CWSI index was calculated and the amount of soil moisture was measured. According to the results, between soil moisture and CWSI index values, the inverse relationship was established with good correlation. Therefore, regression models with linear, exponential, logarithmic, polynomial and power forms were fitted between the above (two) parameters. The best and worst models for estimating soil moisture were the polynomial ( :0.987) and the power ( :0.65) models, respectively. The results showed that the critical values of CWSI index (at the time of increasing leaf surface temperature compared to air temperature), determined the irrigation time. Also, by indirectly estimating the amount of soil moisture, was calculated the soil moisture deficiency and water requirements for irrigation.