Reclamation effects of distinct volumes and concentrations of CaCl2-amended brackish ice in different saline-sodic soils

The proper usage of marginal soil and water resources has major implications for the sustainability of agriculture, such as brackish water and saline-sodic soils. The saline soils can be ameliorated though melting process of calcium-containing brackish ice, however, the optimum concentration and volume of brackish ice (water) for the reclamation of different saline-sodic soils remain to be determined. In this study, 108 soil columns representing four Ice salinity levels (16, 26, 36, 46 mmolc L-1) and three Pore Volumes (2/3, 1.5, 2.5 PV) of calcium-amended brackish ice were tested to reveal the reclaiming effect on a range of saline-sodic soils. The linear mixed model (LMM), multiple regression equation, and principal coordinate analysis (PCoA) were applied to calculate the amelioration effect in terms of three factors: Ice volume, Ice salinity and Column depth. Our results showed that the soil salinity and sodicity generally decreased with increasing Ice volume and Ice salinity, and the saline-sodic soils with low exchangeable sodium percentages (i.e. ESP 20) were more sensitive to Ice salinity, with high salinity (26-46 mmolc L-1) and large volume (2.5 PV) of brackish ice reaching a better amelioration effect. The effect of Ice volume became more dominant in medium and high ESP soils (ESP 40 and ESP 70), whereas the high salinity combined with low volume of brackish ice would lead to worse soil properties, especially at the bottom layers. Meanwhile, the Column depth factor had a considerable effect on the soil chemical properties, with the variance explained ranging from 18.6% to 36.0%. These results provide theoretical guidance in the rational use of calcium-amended brackish ice and highlight the necessity to take layer effect into consideration for reclaiming saline-sodic soils.