Aluminum toxicity in plants and its possible mitigation in acid soils by biochar: A review

Highlights: • Recent knowledge about toxic effects of Al on plant growth are shown. • We provide an overview on how biochar influences soil pH and Al availability. • We summarize recent knowledge about how biochar could mediate Al toxicity in plants. • We suggest that modified biochar could play an important role in Al amelioration. Toxicity of aluminum (Al) is a serious problem for agricultural plants, especially due to excessive soil acidification caused by continuous intensive agriculture and modified environmental conditions related with global climate change. Decreased root elongation and shoot growth, reduced biomass production, nutrient imbalance and altered physiological and metabolic processes are responsible for lower yield and crop quality and therefore, decreased variability and productivity of the land. Recently, biochar is gaining popularity for ameliorating metal toxicity in soils. However, there is a lack of comprehensive information regarding the effects of biochar and its functioning. Multiple mechanisms are involved in ameliorating Al toxicity in which inherent properties of biochar influencing Al adsorption, absorption, complexation, cation exchange and electrostatic interaction are considered to play major roles. Modification of biochar to enhance these mechanisms might hold the key for long term solution. Present review indicates gaps for further research. Long term field studies are needed to understand the effects of biochar on Al toxicity.