Explanation of the Weighting Factor for Salinity Constraint in the Integral Water Capacity Concept (IWC)

The purpose of this study is to present a weighting factor for considering limitation of salinity on plant water uptake (ωsi) for the concept of Integral Water Capacity (IWC). The experiment was conducted under greenhouse conditions and included corn planting in two soil types, three salinity levels (1.5, 4, and 8 dS m-1), and three replications. After the plants were fully established, all pots were continuously irrigated with a specific salinity. The transpiration values were obtained from the weight differences of pots considering water mass balance components at different times. Cumulative transpiration was calculated at each time step and they were plotted against the drainage water salinity at the same time. Then, using the numerical derivative of the cumulative transpiration curves, the transpiration intensity curve was calculated. By fitting a logarithmic model and their relativization, the effect of salinity constraint on the transpiration was calculated and a new salinity weighting coefficient was proposed. The results of ωsi showed that the relative water uptake decreased logarithmically with increasing salinity and the salinity tolerance of corn varied in soils with different properties and a constant value cannot be reported as salinity tolerance.