Water regime enhances the effects of flue gas desulfurization gypsum on the reclamation of highly saline‐sodic soil

Abstract Flue gas desulfurization (FGD) gypsum‐based reclamation of saline‐sodic soil has been widely used in the Songnen Plain of China, but its reclamation effect depends on the water regime. A pot experiment was conducted to identify the optimal water regimes for reclaiming a highly saline‐sodic soil [pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) were 10.4, 5.5 dS m‒1 and 68.1%, respectively] by using FGD gypsum. Three water regimes with drainage times [irrigation amounts of 3‐, 5‐, and 7‐times the soil pore volume (PV)] were selected and FGD gypsum was added to a portion of the regimes before the final drainage operation. Then the saline‐sodic parameters of drainage and soil were measured and analyzed. Na + , Cl − , HCO 3 − , and SO 4 2− were the main ions in the drainage of all the treatments. With the increase in drainage times, the water regime without FGD gypsum notably decreased soil EC by 17.8%–52.0%. In contrast to the FGD gypsum treatment, the water regime failed to decrease the soil ESP. FGD gypsum application with three drainage times had optimal reclamation with reductions in soil pH and ESP of 0.5–2.3 units and 5.1%–20.1%, respectivley. But the associated water consumption was more than 40% higher than that of one‐ or two‐drainage operations. In terms of water reduction (irrigation volume was 5 times PV), sodicity reduction and salt removal (soil pH, ESP, and EC were reduced by 1.7 units, 12.3%, and 1.12 dS m −1 ), FGD gypsum application with two‐time drainage could be a more suitable measure to reclaim highly saline‐sodic soil.