Calcium-modified biochar rather than original biochar decreases salinization indexes of saline-alkaline soil.

We investigated the improvement effects of herbaceous (corn) and woody (oak sawdust) biochar with their calcium modification on saline alkali soil. The addition of unmodified biochar regardless of types had no significant effect on the soluble cations (Na⁺, Ca²⁺, and Mg²⁺) and the main indicators of soil salinity and alkalinity (pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), and total alkalinity (TA)), but the addition of calcium modified biochar decreased these soluble cations and indicators, especially the addition of modified woody biochar (PBM). Compared to CK, TA decreased by 70.02% and 89.25% in PBM with 2% and 4% addition, respectively. Soil ESP and SAR showed a significantly positive correlation with pH and TA, which indicated that soil salinization and alkalization were synchronized. These results showed that the calcium modified biochar, especially the modified woody biochar, instead of the original biochar could be potential soil amendments for the improvement of saline-alkali soil. [ABSTRACT FROM AUTHOR]