Rehabilitation of calcareous saline‐sodic soil by means of biochars and acidified biochars

Abstract Saline‐sodic soils comprise a large area worldwide, and these areas are increasing annually; therefore, reclamation of these soils is necessary. The present study investigated the effects of adding various biochars and acidified biochars on selected characteristics of saline‐sodic soil and rehabilitation of this soil. The biochars were produced from rice straw (RSB) and dicer wood chips (DWCB) at 300°C. The acidified biochars were prepared by adding HCl to the biochars. The biochars and acidified biochars were incorporated to the soil at 0 and 50 g kg−1. Soil columns were prepared and saturated from the bottom, and then the flow was reversed by keeping a 5‐cm constant head of leaching water on top of the columns. The leachates were taken at every one‐third interval of the pore volume fraction. Then, the concentrations of cations and anions, pH, and electrical conductivity (EC) of the collected leachates were determined. At the end of the leaching process, the soil in the column was analyzed for the same parameters as the leachates. The results indicated that the application of the biochars and acidified biochars reduced the soil EC and sodium adsorption ratio. The biochars, especially the RSB, which contains a high amount of Ca2+ and Mg2+, were able to remediate the saline‐sodic soil. The Ca2+ and Mg2+ in the biochar can exchange the Na+ on the surface of the soil colloids and, therefore, enhance the Na+ leaching from the saline‐sodic soil. Acidified biochar induced CaCO3 dissolution, which will add Ca2+ and H+ ions to soil solution. The Ca2+ and H+ ions in the soil solution replace the Na+ from the soil colloid surfaces and facilitate the leaching of Na+ from the saline‐sodic soil. From the results, it can be concluded that RSB, acidified RSB, and acidified DWCB were feasible to ameliorate calcareous saline‐sodic soil.