Application of biochar may help regulate the soil temperature. On one hand dark color absorbs more heat and helps maintain soil temperature, and on the other hand addition of biochar helps in soil aeration, and hence avoiding excessive heating of soil. So, apart from a mild regulation of soil temperature, and subsequent effects of such regulation, there is no stress factor type of biochar.
Rice is hydrophillic and loves high temperature and high humidity too. Temperature stresses may be well tolerated by biochar treatments as compared to normal soils without biochar. It could show sensitivity to stress during reproductive stage but may not in vegetative stage.
Biochar by the virtue of high specific surface is likely to increase water retentive capacity , thereby , improving the water storage capacity of soil to ward off any adverse effect of heat stress of high temperature...