A Model to Predict the Effect of Salinity on Crop Growth

A model is developed to predict the effects of soil salinity on crop growth. As an outgrowth and extension of the modelling efforts of Nimah and Hanks (1973a) and Gupta (1972), this model makes these principal assumptions in order to arrive at a quantitative relationship: 1) relative yield for a growing season is directly related to the ratio of actual and potential transpiration. 2) Water uptake by plants is in response to the water potential gradient between the plant at the soil surface and the soil surrounding the plant roots. 3) the effect of salinity on crop growth is solely due to the effect of osmotic potential in decreasing the water potential gradient. In addition, minor assumptions are made regarding plant cover growth, plant root growth, and separation of E and T from ET. The model was tested to assess its accuracy and was then used to make calculations regarding the relationships of plant growth, irrigation amount and water quality, initial soil salinity, and crop type. Due to the presence of a water table at two meters in the simulations, deep rooted crops showed the best growth under most conditions. Decreases in irrigation and increases in soil salinity were detrimental to crop growth. Irrigation water quality was not effective in decreasing crop growth in one season but was shown to be a factor in long term calculations. Simulations of ten-year management schemes are shown in order to demonstrate long term effects. Finally, a method is presented to evaluate different irrigation systems and calculations are made which compare a flood irrigation system and a sprinkler system