Reclamation of two saline-sodic soils by the combined use of vinegar residue and silicon-potash fertiliser

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Amelioration of saline-sodic soil is essential to increase crop production and preserve the ecological environment in arid and semiarid regions. In this study, a pot experiment was conducted to investigate the effect of combined use of vinegar residue and silicon-potash (Si-K) fertiliser on the physical and chemical properties of two calcareous saline-sodic soils (saline soil (H-soil) and saline-sodic soil (S-soil)) and the growth of oat plants. The results showed that soil electrical conductivity was significantly decreased when vinegar residue was applied in two soils, which could be attributed to that vinegar residue could release H+, and react with HCO3−. When the combination of vinegar residue and Si-K fertiliser were used, equilibrium condition between monovalent cations and divalent cations could be altered. The divalent cations (e.g. Ca2+, Mg2+) were adsorbed at the cost of monovalent cations (Na+), resulting in the reduction of sodium adsorption ratio in the two soils. The decrease in soil pH was mainly due to the decrease in the activity of CO32− and HCO3−, which would react with H+ while vinegar residue was applied. As a saline-sodic soil, S-soil exhibited larger decrease in the pH compared with H-soil, a saline soil. The increase in the relative weight of wet stable macro-aggregate could be attributed to the release of Ca2+ and H+ and the flocculation of the dispersed clay by the application of Si-K fertiliser and vinegar residue. The application of Si-K fertiliser and vinegar residue contributed to a significant increase in survival rate and plant height of oat plants. It also led to increased relative water content and reduced electrolyte leakage for oat plants. This could be ascribed to the improvement of soil aggregate structure and nutrient supply, which promoted selective absorption and transportation of K+ over Na+ and decreased leaf damage. Therefore, the combined use of vinegar residue and Si-K fertiliser was considered to be a wise method for ameliorating two calcareous saline-sodic soils in Shanxi Province, Northern China.