Increases in macroaggregate fractions following organic fertilizer application decrease microbial-driven CO2 release

Summary

Fertilizer application 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 amounts of organic and mineral fertilizers affect microbial-driven CO₂ release at the aggregate scale remains largely unknown. 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 size fractions in organic and mineral fertilized soil. Compared to mineral fertilizer, organic fertilizer increased abundances of carbon decomposition genes, extracellular enzyme activities, microbial residual carbon and CO₂ released from the labile carbon pool, but decreased CO₂ released from the stable carbon pool in microaggregates. Likewise, organic fertilizer increased the proportion of macroaggregates, microbial residual carbon and CO₂ released from the labile carbon pool, but had no effect on carbon degradation gene abundance and extracellular carbon enzyme activity. Taken together, we illustrate that organic fertilizer application decreases CO₂ release via increasing the proportion of macroaggregates, leading to increased carbon storage that can provide a means to lessening atmospheric carbon.