Increases in macroaggregates induced by organic fertilization reduce microbial-driven CO2 release

Fertilization is key for plant yield promotion, but also has side effects on microbes, organic carbon storage and aggregate size distributions. However, links between these factors and especially how different organic and conventional fertilization affect microbial-driven carbon dioxide (CO2) release at the aggregate scale remains largely unknown. In conventionally and organically fertilized soils, we quantified carbon decomposition gene abundance and diversity, microbial residual carbon and CO2 release from the labile or stable carbon pools in three soil aggregate fractions. Organic fertilization increased abundances of carbon decomposition genes and microbial residual carbon, but reduced CO2 release from the stable carbon pool compared to conventional fertilization in microaggregates. Organic fertilization increased the proportion of macroaggregates, microbial residual carbon, but reduced CO2 release from the stable carbon pool and had no effect on carbon degradation gene abundance in macroaggregates. Our study illustrates that organic fertilization reduces CO2 release via increasing proportions of macroaggregates, leading to increased carbon storage that can present a mean to reduce atmospheric carbon.