Practical application of high-sodicity wasteland reclamation with flue gas desulfurization gypsum in the Songnen Plain of China

Based on global food supply demands and the need for sustainable development, it is necessary to rapidly reclaim saline-sodic wasteland as productive land on a large scale. However, the large-scale application of flue gas desulfurization (FGD) gypsum for the reclamation of high-sodicity wasteland to obtain productive fields still lacks quick and concise evaluation indicators. Therefore, four FGD gypsum reclamation practices were applied in high sodicity-affected wastelands. After 6 months, the topsoil (0-20 cm) pH, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), electrical conductivity (EC), and paddy rice yield were evaluated. During the rice harvest, the topsoil pH, ESP, and SAR significantly decreased by 0.9-1.9 units, 29.3-67.2% and 2.3-53.7 (mmol(c) L-1)(1/2), respectively, below initial values. Across the application sites, the interquartile range of the rice yield ranged from 1.7 to 5.8 Mg ha(-1) with a median yield of 3.7 Mg ha(-1). Correlation analysis between the rice yield and topsoil chemical parameters indicated that the soil pH was the primary factor of rice yield reduction, followed by ESP and SAR. To achieve a median yield, we propose that the pH, ESP and SAR of reclaimed topsoil should be lower than 8.7, 27.5%, and 8.5 (mmol(c) L-1)(1/2), respectively, during the first season. This study provides a practical template and reference values for the salinity and sodicity of topsoil when reclaiming high sodicity-affected wastelands via large-scale FGD gypsum application.