Antibiotic resistance genes (ARGs) are emerging contaminants that are widely distributed in agricultural soils and pose potential threats to human health through the soil‒plant system. While straw incorporation and nitrogen fertilization are common practices used to increase soil fertility, their impacts on ARGs remain unclear. This study revealed that wheat straw incorporation increased both the abundance and dissemination potential of ARGs compared with those of maize straw. Moreover, nitrogen amendment at 200 and 400 kya increased the ARG dissemination potential in wheat straw-returning soils. Research findings appeared in Soil Ecology Letters on October 6, 2025.

Previous studies have shown that straw return can increase microbial biodiversity. However, few studies have been conducted under field conditions to investigate the effects of ARGs associated with straw return practices or to compare the effects of different types of straw on ARG abundance and diversity. Researchers from Hebei Normal University and East China Normal University conducted field experiments at the Luancheng Argo Ecosystem Experimental Station, Hebei Province, China. A long-term N fertilization field experiment (> 20 yr) was conducted under different N application levels: N0 (no N fertilizer), N200 (200 kya: kg N ha^‒1 yr^‒1), N400 (400 kya) and N600 (600 kya), with wheat straw incorporated during the summer and maize straw incorporated during the winter season.

Metagenomic analyses revealed that, compared with maize straw return, the incorporation of wheat straw in soils significantly increased ARG abundance (0.54 vs. 0.44 copies per cell) and mobile gene element (MGE; 26.1 vs. 21.6 copies per cell) content in agricultural soils. Moreover, genetic evidence of the coexistence of ARGs and MGEs (distance < 5000 bp) demonstrated that the dissemination potential of ARGs was significantly greater in wheat than in maize straw-returning soils. Glycopeptide, fluoroquinolone and diaminopyrimidine resistance genes were the dominant ARGs and were assigned to Pseudomonadota, Actinobacteria and Firmicutes, which were also the predominant bacteria harboring ARG-MGE.

Compared with the absence of nitrogen amendment or at 600 kya, nitrogen amendment at 200 and 400 kya increased the ARG dissemination potential in wheat straw-returning soils. The different correlation patterns between the dominant ARGs and the carbon and nitrogen metabolism genes implied that bacteria involved in degrading organic substrates and nitrogen metabolism may have antibiotic resistance ability.

Dr Si-Yu Zhang, corresponding author from East China Normal University, said, "We aimed to provide genetic evidence on how common fertilization practices influence ARG spread in real field settings. Unlike prior lab-based studies, our field experiments highlight that wheat straw, combined with moderate nitrogen at 200 and 400 kya, not only enriches ARGs but also enhances their dissemination potential."

Dr. Feng-Hua Wang, first author from Hebei Normal University, added, "Our network analysis revealed distinct co-occurrence patterns, with key bacterial taxa facilitating ARG dissemination. This underscores the need for optimized straw and fertilizer management to mitigate antibiotic resistance in agriculture."

These findings significantly advanced our understanding of the distribution of ARGs in agricultural soils subjected to straw return and nitrogen fertilization practices. Understanding ARG dynamics in soils is crucial for sustainable agriculture and public health, especially considering the co-occurrence of plant and human pathogens with ARGs and MGEs.
DOI：10.1007/s42832-025-0357-4