The study examined the influence of compost and mineral fertilizer application on the content and stability of soil organic
carbon (SOC). Soil samples collected from a long-term field experiment were separated into macroaggregate, microaggregate,
and silt + clay fractions by wet-sieving. The experiment involved seven treatments: compost, half-compost N plus half-fertilizer
N, fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK, and control. The 18-year application of compost increased
SOC by 70.7–121.7%, and mineral fertilizer increased by 5.4–25.5%, with no significant difference between control soil and
initial soil. The C mineralization rate (rate per unit dry mass) in microaggregates was 1.52–2.87 mg C kg−1 day−1, significantly lower than in macroaggregate and silt + clay fractions (P < 0.05). Specific C mineralization rate (rate per unit SOC) in silt + clay fraction amounted to 0.48–0.87 mg C g−1 SOC day−1 and was higher than in macroaggregates and microaggregates. Our data indicate that SOC in microaggregates is more stable
than in macroaggregate and silt + clay fractions. Compost and mineral fertilizer application increased C mineralization rate
in all aggregates compared with control. However, compost application significantly decreased specific C mineralization rate
in microaggregate and silt + clay fractions by 2.6–28.2% and 21.9–25.0%, respectively (P < 0.05). By contrast, fertilizer NPK application did not affect specific C mineralization rate in microaggregates but significantly
increased that in silt + clay fractions. Carbon sequestration in compost-amended soil was therefore due to improving SOC stability
in microaggregate and silt + clay fractions. In contrast, fertilizer NPK application enhanced SOC with low stability in macroaggregate
and silt + clay fractions. 相似文献
Paddy fields are an important source of nitrous oxide (N2O) emission. The application of biochar or the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) to paddy soils have been proposed as technologies to mitigate N2O emissions, but their mechanisms remain poorly understood.
Methods
An experiment was undertaken to study the combined and individual effects of biochar and DMPP on N2O emission from a paddy field. Changes in soil microbial community composition were investigated. Four fertilized treatments were established as follows: fertilizer only, biochar, DMPP, and biochar combined with DMPP; along with an unfertilized control.
Results
The application of biochar and/or DMPP decreased N2O emission by 18.9–39.6% compared with fertilizer only. The combination of biochar and DMPP exhibited higher efficiency at suppressing N2O emission than biochar alone but not as effective as DMPP alone. Biochar promoted the growth of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), while DMPP suppressed AOB and increased AOA. Applying biochar with DMPP reduced the impact of DMPP on AOB. The nirS-/nirK- denitrifiers were decreased and nosZ-N2O reducers were increased by DMPP and the combination of DMPP and biochar. The abundance of the nirK gene was increased by biochar at the elongation and heading stages of rice development. Compared with fertilizer only, the application of biochar and/or DMPP promoted the abundance of nosZ genes.
Conclusion
These results suggest that applying biochar and/or DMPP to rice paddy fields is a promising strategy to reduce N2O emissions by regulating the dynamics of ammonia oxidizers and N2O reducers.