Biochar Effects on Severity Soybean Root Disease Caused By Fusarium virguliforme.

Soil biochar amendments have been shown to decrease soil bulk density and increase soil nutrient and water retention, and under some conditions to improve crop productivity and health.  Several papers have reported the ability of biochar to suppress certain foliar fungal diseases of vegetables.  Our greenhouse and laboratory studies investigated the impact of biochar on the severity of soybean sudden death syndrome (SDS) caused by Fusarium virguliforme.  Soybean plants were grown in pots that contained soil amended with eight different biochars (0 and 20g/kg), which varied in both feedstock and peak pyrolysis temperature, and inoculated with F. virguliforme. Additional laboratory and greenhouse experiments were conducted to study suppression mechanism of biochar application on SDS severity.  We studied i) biochar induced changes in soil physical and chemical properties, ii) the effect of biochar leachates on F. virguliforme spore germination, and iii) induction of plant systemic resistance.  The results indicate that some biochars are effective at suppressing root rot caused by F. virguliforme.  The mechanism of disease suppression was not related to changes in soil properties (bulk density, soil moisture, or soil pH), nor was there a direct effect of aqueous biochar extracts on F. virguliforme spore germination. Results of a split-root experiment showed no clear evidence of biochar applications inducing systemic resistance in soybean plants.  Thus the mechanism by which biochar applications reduce severity of SDS in soybean plants remains unclear.