Assessing the efficacy of ameliorants on saline-sodic soils: Laboratory insights for reclamation strategies

Abstract

This study presents the combined findings of laboratory experiments conducted to assess the efficacy of various ameliorants on saline-sodic soils in the foothill plain of Ile Alatau in the Northern Tianshan region. The investigation focused on the influence of phosphogypsum, elemental sulfur, nano sulfur, and sulfuric acid on the ionic composition of the soil solution and their impact on the soil-absorbing complex. Different doses of these ameliorants were applied to saline-sodic soil samples, and their incubation period was observed. The analysis of the aqueous extract of the soil emphasized the presence of bicarbonate, carbonate, sulfate, calcium, and sodium ions. The results revealed that sulfuric acid was the most effective ameliorant, rapidly neutralizing extreme alkalinity, reducing bicarbonate and carbonate ion content, and increasing sulfate and sodium ion concentrations. Elemental sulfur ranked second in effectiveness, significantly decreasing bicarbonate and carbonate ions and increasing sulfate and sodium ions. Phosphogypsum exhibited the lowest effectiveness, causing reductions in bicarbonate and carbonate ions and modest increases in sulfate and calcium ions. The study demonstrated that the introduction of phosphogypsum led to an increase in calcium and sulfate ions in the soil solution, while elemental sulfur and sulfuric acid significantly increased the sulfate ion content. Sulfuric acid exhibited the highest efficacy among the ameliorants, completely neutralizing normal carbonates and reducing alkalinity in the soil solution. The formation of subsoil gypsum through the interaction of sulfuric acid with calcium carbonates facilitated the displacement of sodium from the soil-absorbing complex. These findings contribute to our understanding of the processes involved in the amelioration of saline-sodic soils and provide insights into effective soil management practices. They serve as a theoretical basis for developing strategies for the reclamation of such soils worldwide. The research highlights sulfuric acid as the most effective ameliorant for saline-sodic soils, resulting in a significant rearrangement of the soil's ionic composition. Further research and field studies are necessary to validate and refine these laboratory findings for practical applications in soil improvement methods.