Improvement in soil organic carbon turnover and microbial community niche differentiation with the addition of commercial organic fertilizers in wheat–green manure systems

Abstract

Background and aims

Green manure and commercial organic fertilizers are widely used in agricultural production to improve the carbon reserves in farmland soil; however, their combined impact on soil organic carbon (SOC) turnover remains unclear.

Methods

We designed a potted wheat–soybean green manure system to investigate the impact of different fertilization treatments on the content and structure of SOC, extracellular enzyme activity and microbial community characteristics in post-wheat harvest soil. For this analysis, fertilization treatment was considered as a single factor.

Results

Compared with chemical fertilization (CF), organic fertilization (OF) led to a 12.5% increase in SOC content, 19.3% increase in the highly active organic carbon fraction and 10.2% increase in the recalcitrant organic carbon fraction (ROC). Furthermore, there was a 16.1% increase in the ratio of alkyl C to O-alkyl C and a 63.4% decrease in the ratio of aliphatic C to aromatic C. The contents of extracellular enzymes, soil total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, microbial carbon and microbial nitrogen also significantly increased. The abundance of the observed species of fungi and bacteria significantly decreased with OF compared with CF, with the symbiotic network indicating a higher level of positive interaction between fungi and bacteria with OF.

Conclusion

OF primarily altered soil enzyme activity by influencing soil nutrient contents, leading to the decomposition of labile organic carbon and an increase in microbial residue biomass, without affecting ROC formation or humification degree. These findings can maximize SOC content in organic agriculture through land-use and fertilization techniques.