The generated watersoluble
Na+ leached downward through the soil when rainfall
occurred (Chun et al., 2001). The decreased concentration of
ExNa resulted in decreased ESP in the topsoil layer (0–10 cm).
The 60 Mg/ha FGD-gypsum reduced soil ESP to the greatest
extent (less than 6.0%). The ESP value of non-sodic soil is
less than 6% in the topsoil or 15% in the subsoil