Effective removal of sodium ion as efflorescence at soil surface using ammonium salts

The existing methods for reclamation of saline-sodic soils are expensive, time-consuming, and require skilled engineering approaches. Therefore, new and fast techniques should be developed for the reclamation of these soils. This study was undertaken to evaluate if harvesting excessive salts via the soil with ammonium hexacyanoferrate (II) (AH) and ammonium perchlorate (AP) [0, 10, 20 and 40 mmol kg^-1] is possible through dendritic crystal growth above the soil surface. Application of crystallization inhibitors increased the concentration of salts on the outer surface and thereby increased pH_e at the top of the soil. Whereas the pH_e of 0-5 cm layers were obtained as 7.30, 7.36 and 7.84, it increased to 9.94, 9.84 and 8.45 in 15-20 cm layers with 10, 20 and 40 mmol kg^-1 AH application doses, respectively. Except for 5-10 cm of control and 10 mmol kg^-1 AP application, the lowest pH_e values were obtained from the 0-5 cm and gradually increased from bottom to top. For all AH and AP application doses, the highest electrical conductivity (EC_e) values were obtained from the 15-20 cm and significantly increased from bottom to top. Application of AH and AP have transformed exchangeable Na⁺ to water-soluble Na⁺ and this situation has caused an increase in the concentration of water-soluble Na⁺ throughout the soil column. AH and AP applications have decreased exchangeable sodium percentage (ESP) in all of the layers. Whereas the ESP of control was 70.07% in 0-5 cm layer, it decreased to 62.44, 55.63 and 53.76% with 10, 20 and 40 mmol kg^-1 AH application doses, respectively. Similar decreases were obtained for 5-10, 10-15 and 15-20 cm layers. Results obtained have shown that application of AH and AP to saline-sodic soil is an effective reclamation material to remove salts from soil surface within a short time, particularly in arid climates.