Crop salt tolerance data have traditionally been analyzed with a three parameter threshold-slope model that assumes maximum yield until salinity threshold value, and a linear decrease in yield beyond the threshold. This study shows that an alternative. S-shaped response model provides an equally good or better fit to many experimental data sets and with less bias in the parameter estimation process. Analysis of 204 data setsfrom the original database compiled by Mass and Hoffman (1977) revealed that a single dimensionless curve could be used to represent the salt tolerance of most crops. The curve is given by Yr = 1/[1 +(c/C50)3], where Yr is the relative yield, c the average root zone salt concentration, and C50 a parameter which describes the degree of salt tolerance of the crop (the average root zone salinity at which the yield has declined by 50%). The presence of a unique dimensionless curve to describe the salt tolerance of many or most crops may point to some common mechanism that could govern the yield response of crops to salinity, and perhaps to other yield limiting factors as well.
Salt tolerance, response function, soil salinity, yield-limiting factors
