Abstract: Salinization reduces the productivity of soils. Exploring the effects of biochar on salt tolerance of rice seedlings under salt stress is important to regulate rice production potential in saline areas. In this study, the effects of biochar on soil environment and salt tolerance of rice seedlings under salt stress were examined in a pot experiment. There were four levels of salt concentrations: 0 g NaCl·kg^-1 soil (S0), 1 g NaCl·kg^-1 soil (S1), 2 g NaCl·kg^-1 soil (S2), and 3 g NaCl·kg^-1 soil (S3). There were two levels of Biochar applications: 0 g biochar·kg^-1 soil (C0) and 3 g biochar·kg^-1 soil (C1). The results showed that biochar application in salt stressed soil significantly increased aboveground biomass and agronomic characters of rice seedlings. Biochar application significantly increased total K content in the stem of rice seedlings and enhanced K/Na ratio in rice seedlings by 79.61%. Biochar application greatly improved the antioxidant abilities of rice seedlings and reduced the MDA content of leaves by 14.25%. Biochar application inhibited membrane lipid peroxidation of rice seedlings and alleviated the negative effects of salt stress on rice seedlings. After the harvest of rice seedlings, soil watersoluble Cl^- and Na⁺ contents under biochar treatments were significantly decreased by 9.13% and 17.77% respectively. Our results showed that applying appropriate amount of biochar in the soil can effectively reduce soil watersoluble salt content, improve the salt stress of soil, and enhance the adaptability of rice seedlings to the saline soil.

Key words: biochar, salt stress, rice seedling, salt tolerance.