Salinization and sodicity are obstacles for vegetation reconstruction of coastal tidal flat
soils. A study was conducted with flue gas desulfurization (FGD)-gypsum applied at rates
of 0, 15, 30, 45 and 60 Mg/ha to remediate tidal flat soils of the Yangtze River estuary.
Exchangeable sodium percentage (ESP), exchangeable sodium (ExNa), pH, soluble salt
concentration, and composition of soluble salts were measured in 10 cm increments from
the surface to 30 cm depth after 6 and 18 months. The results indicated that the effect of
FGD-gypsum is greatest in the 0–10 cm mixing soil layer and 60 Mg/ha was the optimal rate
that can reduce the ESP to below 6% and decrease soil pH to neutral (7.0). The improvement
effect was reached after 6 months, and remained after 18 months. The composition of
soluble salts was transformed from sodic salt ions mainly containing Na+, HCO3
− + CO3
2− and
Cl− to neutral salt ions mainly containing Ca2+ and SO4
2−. Non-halophyte plants were
survived at 90%. The study demonstrates that the use of FGD-gypsum for remediating tidal
flat soils is promising.