Changes in Soil Salinity in Sugarcane Root Zones According to Irrigation Method and Drainage Using SaltMod in Imam Khomeini Agro-Industry

Sugarcane, which has high water requirements, is grown in Khuzestan province (Iran). Climate and optimizing the use of water is very important to sustainable cultivation of sugarcane. Studies of water requirements for sugar cane in Khuzestan show that in parts of sugarcane agro-industry, the water applied is more than the actual water requirement of the plant. The present study was conducted to predict the long-term effects of irrigation system and drainage in the Imam Khomeini sugarcane agro-industry on soil salinity, drainage depth, water table and irrigation sufficiency and efficiency using the SaltMod model. The model varied the irrigation depth and drainage control factor (Frd) to decrease subsurface drainage depth and salinity of irrigation water. Model output was calibrated using field data. The model predictions showed that a drainage control factor of more than 0.25 without a decrease in irrigation water caused the water table to rise. A 20% decrease in irrigation water and an assumed drainage control factor of up to 0.5, there was no change in soil salinity or water table depth. Drainage outflow depth of about 2.07 m decreased to 1.26 m during irrigation. The SaltMod model predicted that increasing the subsurface drainage depth to over 1.5 m would not improve yield or change soil salinity. If the irrigation water had salinity levels of >1.7 dS/m, soil salinity in the root zone will be >3 dS/m.