Abstract:

A rice field experiment was conducted in Jiujiang city, Jiangxi province, from 2023 to 2024, with the following eight treatments of no nitrogen fertilizer (N0), conventional nitrogen application (N100), 20% nitrogen reduction (N80), 20% nitrogen reduction with different amounts of microalgae biofertilizer (M1N80, M2N80 and M3N80), 20% nitrogen reduction with biochar (BN80) and 40% nitrogen reduction with microalgae biofertilizer (M4N60). This study aimed to assess the impacts of nitrogen reduction combined with microalgae biofertilizer and biochar treatments on soil organic carbon (SOC) and its components in paddy fields to provide a scientific basis for enhancing SOC content and improving soil carbon sequestration potential. The results showed that the mineral−associated organic carbon (MOC) accounted for 60.3%−76.5% of the total soil organic carbon. Compared with the N100 treatment, both M3N80 and BN80 treatments significantly increased MOC content by 45.3%−46.8% (P<0.05), which in turn contributed to a 27.6%−34.3% increase in total SOC content. The 20% nitrogen reduction with microalgae fertilizer and biochar significantly increased soil dissolved organic carbon (DOC) by 9.8%−260.0% and microbial biomass carbon (MBC) by 10.7%−120.0% during key rice growth stages. The results demonstrate that biochar and high−dose microalgae biofertilizer (M3N80) application exhibit optimal performance in enhancing SOC content in paddy fields, confirming that exogenous organic inputs can improve SOC stability, thereby providing a novel component−regulated fertilization strategy to enhance carbon sequestration capacity in rice ecosystems. 

Key words: Fertilization control, Rice paddy, Soil organic carbon component, Microalgae biofertilizer, Biochar