Comparison of models that include salinity and matric stress effects on plant growth

Steady-state models provide the means to evaluate potential effects of the amount of applied water and its salinity on crop yields. These models have been in use since about 1950. Because of the inherent limitations of steady-state models, transient-state models have been under development by several research groups since about 1980. The objective of this research was to determine how the models handle matric and osmotic stress effects on relative crop ET and consequently relative crop yield. In transient-state models, crop water use and crop yields account for the continually changing soil salinity (osmotic potential) and soil water contents (matric potential) that occur throughout the rootzone resulting from changes in irrigation water salinity, amounts of applied water, rainfall, and climate. Under conditions where crop water use is not limited by either matric or osmotic potentials or hypoxic conditions, these models assume that relative crop ET, and relative yields for forage crops, increase linearly with increasing amounts of crop water use in the range from zero to maximum potential ET. The models account for changes in this linearity if either matric or osmotic potential exceeds threshold levels.