To understand the effects of salinity stress on four growth stages of sorghum, including: emergence to growing point differentiation, growing point differentiation to half bloom, half bloom to soft dough, and soft dough to physiological maturity, a greenhouse experiment was carried out with 10 treatments, considering all possible combinations of salinity stress and salt- free periods. Salinity stress during early growth and panicle differentiation declined the plant height and tiller number. The highest biological yield was for the control, but the lowest when plants were salinized all throughout the growing season. when plants were stress-free at 2-3 early stages and then subjected to salt stress, reduction in total dry matter were remarkably less than those that salinity imposed in their later growth stages, especially if salinity occurred at a late individual stage. Continuation of salt stress from emergence to both blooming and soft dough stages led to remarkably adverse effect on grain yield. The effect of salinity appears to be most pronounced on yield components that are growing or developing at the time the salt stress is imposed. The critical period of salinity stress for biological yield was much distinct than that of the grain yield. The maximum duration of salinization, at both thresholds of 10% and 20% yield loss was more for grain yield than that of biological yield, and, the minimum duration of salinity-free at both thresholds was less for grain yield. This indicates that sorghum is not sensitive to salinity at seed setting and seed filling period.

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