Co-application of biochar and silicon fertilizer enhances rice nutrient allocation, soil fertility, and mitigates ARG dissemination in paddy soil.

Abstract

The restoration of soils contaminated by antibiotic resistance genes (ARGs) is essential for agricultural safety and human health. Although biochar and silicon (Si) fertilizer have been commonly applied individually as amendments for soil remediation and rice quality improvement, their combined effects remain unclear. Here, we systematically assessed the effects of the integrated application of biochar and Si fertilizer on rice nutrient uptake, soil properties, bacterial community structure and functions, and ARG abundance by conducting a 120-day pot experiment with four treatments: control (CK), 0.15 t ha-1 of Si fertilizer (SF), 3 t ha-1 of biochar (BC), and their combination (SC). The results showed that the combined treatment enhanced rice panicle length and promoted the translocation of Si and potassium to leaves, while altering the distribution of nitrogen and phosphorus in rice. In soil, co-application did not markedly alter pH, SOM, or most available nutrient levels, but significantly increased TN and TP contents. Moreover, the SC treatment resulted in the lowest abundances of detected ARGs and MGEs among all treatments. It also reshaped the bacterial community composition and functional profiles, including reduced abundance or functional contribution of key r-strategist genera associated with ARGs and nitrogen/phosphorus metabolism, such as Dinghuibacter and Roseomonas. Overall, the co-application of biochar and Si fertilizer improved rice nutrient supply, enhanced soil nutrient status, and mitigated the dissemination of ARGs. These findings provide a scientific basis for sustainable paddy field production and ARG risk management in paddy ecosystems.