Sodic soil is more likely to deteriorate in paddy fields than in other fields. Flue gas desulfurization (FGD) gypsum can reclaim sodic soils, but how long a one-time application of FGD gypsum provides benefits in paddy fields is poorly understood. In this study, soil salinity, sodicity, and soluble and exchangeable cation concentrations were evaluated over a 7-year period to investigate the reclamation of sodic soil in a paddy field by FGD gypsum. After 7 years, compared with those in the initial soil, the pH, sodium adsorption ratio, and exchangeable sodium percentage of the topsoil (0–20 cm) decreased by at least 2 units, 72.2% and 80.9%, respectively. In the process of FGD gypsum reclamation, substantial changes in topsoil salinity and sodicity occurred mainly between the 4th and 5th years of reclamation, representing the boundary of the FGD gypsum dissolution stage, which was followed by the soil reclamation maintenance stage. In the FGD gypsum dissolution stage, soil salinity was dominated by Ca²⁺ that accumulated in the 0–10 cm soil layer. Over time, the exchangeable Ca²⁺ concentration decreased with soil depth to 40 cm. In the reclamation maintenance stage, FGD gypsum was basically depleted, but the sodicity still showed a significant decrease compared with that in the initial soil. These results indicate that FGD gypsum can significantly and effectively reclaim sodic soil in paddy fields for at least 7 years. Though the FGD gypsum was exhausted 5 years after its application, reclamation continued to be maintained due to the presence of exchangeable Ca²⁺.

中文翻译：

---

烟气脱硫石膏一次性施入稻田后土壤盐碱度变化

与其他田地相比，稻田中的钠质土壤更容易变质。烟气脱硫 (FGD) 石膏可以回收钠质土壤，但人们对一次性使用 FGD 石膏在稻田中的效益了解得很少。在这项研究中，对土壤盐度、碱度以及可溶性和可交换阳离子浓度进行了 7 年的评估，以研究 FGD 石膏对稻田中碱土的复垦。7年后，与初始土壤相比，表土（0-20 cm）的pH值、钠吸附率和可交换钠百分比至少下降了2个单位，分别为72.2%和80.9%。在 FGD 石膏复垦过程中，表层土壤盐度和碱度的显着变化主要发生在复垦第 4 年和第 5 年之间，代表 FGD 石膏溶解阶段的边界，然后是土壤复垦维护阶段。在 FGD 石膏溶解阶段，土壤盐分以 Ca 为主²⁺在 0-10 cm 土层中积累。随着时间的推移，可交换 Ca ²⁺浓度随土壤深度降低至 40 cm。在复垦维护阶段，FGD石膏基本耗尽，但与初始土壤相比，碱度仍显着下降。这些结果表明 FGD 石膏可以显着有效地回收稻田中的钠质土壤至少 7 年。尽管 FGD 石膏在其应用 5 年后耗尽，但由于存在可交换的 Ca ²⁺，回收继续保持。