Using biochar for the treatment of continuous cropping obstacle of herbal remedies: A review

With the increase of cultivated varieties of Chinese herbal remedies, the continuous expansion of cultivation area, and long–term monoculture cropping, the problems of soil diseases, yield loss and quality reduction are becoming increasingly aggravated. Continuous crop obstacle has been a limiting factor which strongly affects the yield and quality of Chinese herbal remedies. Various measures have been used to alleviate continuous crop obstacles, however, they have not been able to effectively address such problems. As a carbon-rich material, biochar can significantly improve soil quality which provides a promising way to alleviate continuous crop obstacles of Chinese herbal remedies. In this paper, we summarized the detriments and causes of continuous crop obstacles in Chinese herbs, and reviewed the agronomic measures and physicochemical control methods proposed to cope with such problems. The research progresses on the role of biochar in the alleviating continuous crop obstacle problems, including the improvement of soil properties and soil microbial community structure, inhibition of the self–toxic effect by allelochemicals of herbs were discussed. Future research on how biochar affects the allelopathic substances that secreted by Chinese herbal remedies should be conducted. This review will provide a theoretical basis and technical support on how to use biochar to mitigate the continuous crop obstacle of medicinal herbs.