This study was done in ehe wet marginal part of the Siahkooh
playa (Kevir) in Yauf. Iran. which is located in the northwest of Ardakan.
The abundance of Ca and SO. iones led to gypsum crystallization ncar the
water table in the soil. From depeh to the soil surface, the caC~- CaSO ..
,2H,O -NaCI-H,<)-PCo, soil and water system change to CaSO •• 2H,<)Na1SO
.. ·NaCI· Hz{). From water table (I00cm under soil surface) to the soil
surface. ionic power was decreased and activty coefteient was incrased
respctivcly. Therefore. ncar ground table, gypsum fonn and high
concentration of Ca iones from gypsum lead to low amounts of
exchangeable Na. This influence has been continued up to soil surface to
achieve a relative balance. Replacement ofNa with Ca on the exchangeble
surfaces of soil and ex~ of SO .. ioncs formed NaSO .. ineraJs. The
precipitation of 1800ton per hectar natrium salts(sulfatic &. coloridic) was
estimated wjth respect to the mean of annual evaporation (roughly 900mm)
in the studied site. The result also showed that the seventh bands ofI .. odsal7
are more important to diferentiate between sulfate and chloride salts as well
as sodium and calcium salts.