Computer model for managing saline waters for irrigation and crop growth

A computer model was developed primarily to help formulate irrigation strategies for areas where saline waters of questionable quality may be an option for crop production. The model estimates salt and water balance in the soil profile and predicts crop growth, given a certain irrigation and crop rotation strategy.; The model was calibrated and tested for wheat and sorghum crops using one year's data from column lysimeters at the U.S. Salinity Laboratory at Riverside, California. It was found that evapotranspiration from these lysimeters was very much on the high side because of several effects. A factor relating these effects to average daily temperature was used in the model to take care of the high evapotranspiration recorded at the site of the lysimeters. Results using this factor were found to fit the lysimetric data very nicely.; Salinity effects on crop growth are simulated in the model through inclusion of osmotic potential in the water uptake equation. However, it was found that osmotic potential alone may not be the only factor responsible for reduced crop growth under heavy and frequent irrigations. Effect of salinity on root metabolism affecting permeability across root membranes was considered as a probable cause of plant water stress and a factor relating root permeability to soil water salinity was used in the water uptake function. The model was found to behave very nicely once it was calibrated for this effect.; The model is designed to be useful for any location. A typical location in Pakistan representative of irrigated agriculture with saline water was selected to demonstrate the use of the model as an example. It is recommended that the model should be calibrated and verified with data from field scale experiments before being used as a decision making tool. More research is also recommended to test the hypothesis that root permeability to water flow is a function of soil water salinity under high evaporative demands.