Biochar, compost and arbuscular mycorrhizal fungi: a tripartite approach to combat Sclerotinia sclerotiorum in soybean

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a major disease in soybean in many parts of the world. Sustainable control measures to combat this pathogen can be better achieved by combining different available tools. One element to control fungal diseases could be changing biological activities by adding organic matter inputs, such as biochar and compost, to the soil. Other players are arbuscular mycorrhizal fungi (AMF); bioprotective effects have already been documented for them. In the present study, we assessed the effect of organic matter inputs, such as compost alone at the application rate of 20% of the total substrate (v/v) and/or green waste biochar at the application rate of 3% (v/v) in combination with or without arbuscular mycorrhizal fungi, against Sclerotinia sclerotiorum and their effect on plant growth characteristics in soybean. Substrates including compost resulted in a lower disease severity in both, plants inoculated and non-inoculated with AMF. The AMF root colonization was highest in plants grown in the control treatment and green waste biochar substrate inoculated with Sclerotinia sclerotiorum; the lowest colonization was found in plants grown in substrates containing compost. Soil substrates, especially compost, affected shoot dry matter production in soybean plants inoculated with Sclerotinia sclerotiorum and in non-inoculated plants; compost alone was superior in treatments with and without AMF. Root morphological traits were more strongly influenced by AMF than by the substrate. Our findings suggest that compost has a positive effect in terms of soybean growth and diseases suppression, which is more pronounced than that of biochar and AMF.

Automated summary

Sustainable control of Sclerotinia stem rot in soybean can be achieved by combining organic matter inputs like compost and biochar, along with arbuscular mycorrhizal fungi. These methods effectively reduce disease severity, enhance plant growth characteristics, and show positive effects on soybean growth and disease suppression.