Initial changes in soil microbial community structure after combined biochar and straw application to agricultural soil: evidence from a 180-day incubation experiment

Organic amendments are applied to agricultural soils to maintain fertility and function. In the present study, we monitored the CO2 emissions and analyzed the microbial biomass, community structure, and network complexity under single and combined applications of maize straw and maize straw-derived biochar (550 °C, 2 h) during a 180-day incubation experiment. The cumulative CO2 emissions were ordered as straw > biochar + straw > biochar, and the CO2 emissions in the biochar + straw treatment were 41%–51% lower than those of the straw-only treatment. The content of phospholipid fatty acids (PLFAs) was not affected by biochar but increased under straw (p < 0.05) and decreased by 1.9%–46% under the combined treatment compared with the straw-only treatment, suggesting that microorganisms had various demands for nutrients. The greatest effects of applying organic material on the microbial community were found at the end of incubation under biochar, but at the start of incubation under straw addition, based on the nutrient supply provided by the type of material input. Biochar + straw strengthened cooperation between microorganisms by enhancing network complexity and alleviating competition in the network structure. Therefore, biochar + straw had an optimized effect on mitigating CO2 emissions and stimulating microbial community development compared to straw-only. © The Author(s) 2025.