This study was conducted to evaluate the reclamation potential of saline and sodic soils in the Sistan Plain, determine leaching water requirements for salinity reduction, and assess the necessity of gypsum application for sodic soil reclamation. Three representative sites from the Akbarabad, Charak, and Arbab soil series with different salinity–sodicity classes were selected. Leaching was performed using intermittent ponding with a total of 1 m of water applied in four successive 25cm increments. Gypsum was also applied at rates of 13.5 and 34 t ha⁻¹ in two of the study sites.
The results showed that in the Akbarabad profile, with an initial average electrical conductivity (ECe) of 11.5 dS m⁻¹, approximately 45 cm of leaching water was required to reduce the salinity of the upper 50 cm of soil to about 2 dS m⁻¹. In the Arbab profile, about 58 cm of net leaching water reduced the salinity of the upper 50 cm of soil to 6 dS m⁻¹. In contrast, in the Charak profile, characterized by an initial ECe of 65.3 dS m⁻¹ and an exchangeable sodium percentage (ESP) of about 73%, application of 1 m of leaching water together with 34 t ha⁻¹ of gypsum reduced salinity only to 14 dS m⁻¹ and ESP to 49.5%. Moreover, gypsum application did not significantly improve soil permeability or enhance the reduction of salinity and sodicity compared with leaching alone. The findings indicate that the reclamation potential of saline and sodic soils in the Sistan Plain is strongly controlled by soil physical and chemical properties. Leaching alone was effective in soils with favorable permeability, whereas in heavy-textured soils with low permeability, even large amounts of water and gypsum resulted in limited improvement. Therefore, leaching requirements and amendment application should be determined according to site-specific soil conditions and regional water limitations.