The ESP in the 10–20 cm soil
layer was decreased most by the 60 Mg/ha FGD-gypsum
treatment, closely followed by the 45 Mg/ha FGD-gypsum
treatment. No obvious effect was observed in the 20–30 cm
soil layer. A similar trend happened after 18 months. The ESP
in the FGD-gypsum treatments had an increasing trend with
increasing soil depths, ESP0−10 < ESP10−20 < ESP20−30