Fungi boost biochar and compost carbon storage in nutrient poor urban soils, study finds

A new field study from Shenyang Agricultural University shows that adding biochar and compost to urban soils can significantly increase carbon storage, but only in nutrient poor greenspaces. The key factor is the soil's fungal community. In low fertility soils, fungi thrived after amendment and helped lock carbon in place. In nutrient rich soils, the same treatments reduced fungal diversity and accelerated carbon loss. The experiment was run across three types of urban greenspace in Beijing. In nutrient poor sites, carbon and nitrogen gains were up to 14 times higher than in fertile soils. The authors say city managers should prioritize low fertility parks and lawns for biochar and compost application rather than applying them everywhere. This targeted approach could improve urban carbon storage and soil health without wasting resources on sites where the carbon would not stay.