Adapting the DSSAT Cropping System Model to Saline Soils.

In arid and semi-arid zones the extent and degree of soil salinization is increasing, particularly when the irrigation water contains significant amount of soluble salts affecting on crop production. To properly manage this process, it is necessary to quantify the movement of salts in the root zone and to determine the ultimate impact on yield. Due to the complicated character of water and solute movement in the soil, the spatial variability of soil properties and the variability in weather conditions the crop models play an important role in the quantification of soil salinity effects on yield. Currently, the Cropping System Model(CSM) of the Decision Support System for Agrotechnology Transfer(DSSAT) does not include the effect of soil salinity on crop growth and thus limits its application for certain conditions. The objectives of this study were to include a salinity module into CSM and to compare modified with the original CSM in its capability to correctly simulate yield, yield components and water use under saline conditions. The new salinity module modifies the water stress factors that ultimately impact growth and development. The plant water status is linked to the soil texture and to soil water salinity, while root water uptake(RWU) is modified  to account for soil salinity. Soil salinity reduces RWU relative to potential uptake and is calculated as a function of soil salinity, cultivar characteristics relative to salt tolerance and the relative rate of reduction in water use due to salinity, stomatal closure and a reduction in photosynthesis compared to non-saline conditions. Computer simulations for different crops and environments were conducted to assess the effects of salinity response. The results showed a reasonable agreement between simulated and observed data. The modified CSM may represent a useful tool to define the best water management under saline conditions and for salinity risk evaluation.