Mitigative Effect of Biochar on Aluminum Toxicity of Acid Soil and the Potential Mechanism
[Objective] Aluminum toxicity of acid soil is one of the hot topics in soil science research,and biochar with some bio-characters give a new method to solve this problem.The objective of this experiment is mainly to clarify the mitigative effect of biochar on aluminum toxicity of acid soil and the potential mechanism.[Method] An experiment including CK (0C+0Al),C (2％C),Al (1 mmol·L-1Al),and C+Al (2％C+1 mmol·L-1Al) treatments indoor planting pakchoi in pots added with biochar and exogenous aluminum was conducted.The effects of biochar on different active aluminum and the growth of crop of aluminum enrichment red soil were analyzed.[Result] The results showed that aluminum toxicity significantly decreased the emergence rate of pakchoi.The growth of pakchoi restrained significantly and the biomass of pakchoi decreased under aluminum toxicity,meanwhile,the Al content of the pakchoi increased significantly under aluminum toxicity.However,the growth of pakchoi improved significantly and the Al content reduced under biochar addition,and the aluminum content of C+Al treatment pakchoi reduced by 89.4％ compared with Al treatment.Aluminum toxicity decreased the pH of the red soil,the pH of Al treatment decreased by 0.36 compared with CK treatment,but the pH of the red soil increased significantly under biochar addition,the pH of C+Al treatment increased by 0.62 compared with Al treatment.The active aluminum of Al treatment was 276.4 mg·kg-1 more than CK treatment.Application of biochar decreased the active aluminum of red soil,and the active aluminum in C+Al treatment decreased by 14.9％ compared with Al treatment.Besides,the exchangeable Al3+ of Al treatment increased by 23.1％ compared with CK treatment,but the exchangeable Al3+of C+Al treatment decreased by 46.5％ compared with Al treatment.The main active aluminum form of CK and Al treatment soil was the exchangeable Al3+ that had biological toxicity,the main active aluminum form of C and C+Al treatment soil was dimer hydroxy aluminum ion and colloid Al(OH)30.[Conclusion] Exogenous aluminum had a strong stimulating effect on the addition of active aluminum of red soil.Exchangeable Al3+ which has biological toxicity increased significantly under aluminum toxicity.Besides,adding exogenous aluminum can decrease the pH and stimulate the poison,restrain the growth of the crops.Although application of biochar can increase the pH and ease the aluminum toxicity of red soil,its effect on different 4 forms of active aluminum has a quite large difference.Application of biochar can reduce the poison by decreasing the exchangeable Al3+ which has biological toxicity,and thus improve the growth of crop.
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