Biochar mitigates the negative effect of chloropicrin fumigation on beneficial soil microorganisms.

Chloropicrin (CP) is the most commonly used soil fumigant worldwide. Although CP effectively controls soilborne pathogens, it is also detrimental to beneficial soil microorganisms unless measures can be put in place to protect them from the effects of fumigation. In this study, we evaluated the ability of biochar made from the invasive weed Eupatorium adenophorum to mitigate the effects of CP fumigation on beneficial species. Our results showed that the addition of biochar to the soil effectively reduced the detrimental effects of CP on beneficial species and their ecological functions. Biochar added to CP-fumigated soil shortened the time to 28-84 days for microbial diversity and nitrogen cycle functions to be restored to unfumigated levels. At the same time, the inorganic nitrogen (NH4+-N, NO3--N) content and N2O production potential level in CP-fumigated soil returned to unfumigated levels relatively quickly, which showed that nitrogen metabolism improved with the addition of biochar. The mitigation effect of biochar in CP-fumigated soil was more evident at higher biochar amendment rates. Our results suggest that the addition of biochar to CP-fumigated soil significantly reduced the impact of CP on beneficial species and their ecological functions, and significantly shortened the time for beneficial species to recover to pre-fumigation levels. Field research is required to determine biochar's ability to mitigate the impact of CP and other fumigants on beneficial species and to quantify its benefits on crop quality and yield.