Biochar and mycorrhizae: a combination with potential
Biochar can provide a habitat and carrier for mycorrhizal fungi. Rodale Institute, USDA and university research examines agricultural uses.
Arbuscular mycorrhizal fungi partner with many plants, extending hyphae into soil and helping nutrient uptake, especially phosphorus. Plants supply photosynthetic carbon. Biochar is carbon-rich material produced by heating biomass with limited oxygen; its porous structure is of microbial interest.
The Rodale and USDA experiment
Douds and colleagues examined pelletised biochar as a fungal carrier in 2014. They used compost and vermiculite with Paspalum notatum as host, testing biochar pellets and expanded clay granules. Recovered pellets transferred fungi to new plants. In that experiment, even 0.1 g produced colonisation in test plants. This is an experimental finding, not a general application rate.
The work suggests a carrier form potentially suitable for mechanised inoculant application.
Which fungi colonise biochar?
Neuberger and colleagues placed biochar in mesh bags in different agricultural soils in 2024. Mesh admitted hyphae but excluded roots. Colonisation was selective: only part of the surrounding mycorrhizal community entered, with notable Paraglomus representation. Biochar is a particular microhabitat used differently by fungal groups.
Water shortage
Mickan and colleagues studied biochar, mycorrhizae and subterranean clover in a 2016 greenhouse experiment. Under limited water, woody biochar was associated with greater shoot biomass, root colonisation, external hyphal length and shoot phosphorus. Effects with adequate watering were small, illustrating context dependence.
From findings to application
These studies address different questions: fungal transport, colonisation and drought response. A farm comparison should assess biochar alone, inoculum alone, their combination and an untreated area. Record biochar type and quantity, crop, irrigation, growth and yield. Root colonisation assessment supplies essential biological information.
Our field work
We have not yet tested this combination. It is a future plan requiring careful preparation for appropriate mycorrhizal establishment.