Biochar contributes to resistance against root rot disease by stimulating soil polyphenol oxidase

Biochar has been considered an effective approach as soil amendment for decreasing incidences of disease and regulating microbial populations in continuous-cropping soil.Although researches have extensively focused on changes of soil microbes and unbalance of nutrition in continuous-cropping soil,the relationship between soil properties and pathogens by biochar application remains poorly understood.In this study,we applied ITS ribosomal RNA gene profiling to analyze tobacco root microbiota of biochar and non-biochar treatment in a 3-year continuous-cropping tobacco field,comparing firstly planting tobacco as control.We found that biochar application decreased the relative abundance of the soil fungal pathogens(Ceratobasidium and Monosporascus),which are the prime pathogens of tobacco root rot in continuous-cropping soil.Using RDA,co-occurrence and PLS-PM approaches,we provided evidence that there was a negative correlation between fungal genera(especially for Ceratobasidium and Monosporascus)and soil polyphenol oxidase(PPO)activity(R^(2)_(incidence rate)=−0.930,R^(2)_(disease index)=−0.905,both p<0.001).The PPO was up-regulated by different biochar treatment intensities.Together,we demonstrated that biochar in continuouscropping soil regulated the soil PPO activity to suppress pathogens,and further decrease incidence of root rot.Notably,biochar application forward continuous cropping was more effective for the continuous-cropping soil improvement than the other treatments.The data should help in appropriate timing of biochar application for alleviating continuous-cropping obstacle.

Development of the straw biochar returning concept in China

Biochar produced from straw has been shown to improve soil physicochemical properties.This review introduces the fundamental concepts,the broad applications,and underlying theory of straw biochar returning.Current developments in biochar industry and the production practices prevalent among enterprises in China are critiques.This review analyzes current knowledge gaps,challenges,and opportunities in the industrial application of straw biochar returning.Biochar standards,the quantitative and qualitative analysis methods for biochar,and high-value-added products that are based on biochar are critically examined with goal of providing recommendations for future studies.We propose production and modification of biochar that is application oriented to enhance its fitness for purpose as well as long-term and large-space-scale field study to better understand its impact on soil properties and ecotoxicology.Finally,we make prospects for the future development of SBR,including constructing a standard system about straw biochar returning and promoting self-discipline of biochar industry and the establishment of a biochar-based agricultural production model.