In arid/semi-arid regions, strategies to enhance soil water retention are critical for crop productivity. This study elucidates the synergistic regulatory mechanisms of biochar and soil water regulation on maize root growth and photosynthesis. An integrated pot experiment (2023) with three biochar (0, 7.5, 15 t ha⁻¹), a field experiment (2024) with two biochar (0, 7.5 t ha⁻¹), and three soil water gradients (sufficient water, moderate drought, and severe drought) were conducted. Pot results showed that biochar applied at 7.5 t ha⁻¹ significantly increased soil-saturated water content by 11.4% and residual water content by 4.7% compared to the control, as confirmed by the fitting van Genuchten model (R² > 0.94). Maize roots were primarily concentrated in the 5–15 cm soil layer, with root weight density (RWD) increasing by 21.0% under 7.5 t ha⁻¹ biochar treatment. The field experiment based on the pot results showed that biochar attenuated the drop in net photosynthesis (Pn) and stomatal conductance (Gs) under drought, reducing Pn and Gs decline by 24.5% and 21.4%, respectively, and suggesting improved efficiency. The study indicates that 7.5 t ha⁻¹ biochar optimizes maize root growth and photosynthesis through improved soil hydraulic properties, providing a sustainable strategy for arid and semi-arid regional agriculture.

Organic fertilizer substitution offers a sustainable approach to crop production, but its impacts on plant–soil–microbial stoichiometry and rhizobacterial communities are poorly understood. A field experiment was conducted with six fertilization regimes, all fertilization treatments were designed to have equal N input: CK (control, no fertilizer), IF (chemical fertilizer), TF20, TF30, TF50 and TF100 (20%, 30%, 50% and 100% of chemical N replaced by organic fertilizer, respectively). Our results showed that compared with IF, TF20 maintained maize yield and increased nitrogen use efficiency(NUE) by 22% and plant N and P uptake by 14% and 19%. Higher substitution rates reduced phosphorus use efficiency(PUE), and 100% substitution decreased NUE by 85% and yield. However, soil total C and N concentrations and soil C:N:P ratios were unaffected by fertilization at either growth stage, indicating strong homeostatic buffering of soil C:N:P stoichiometry within one growing season. At maturity, TF20 showed an elevated microbial biomass C:P (MBC:MBP) accompanied by increased sucrase activity but no significant increase in phosphatase activity, suggesting a carbon driven stoichiometric adjustment rather than phosphorus limitation. In contrast, phosphatase activity was significantly higher under 30% and 50% substitution at maturity, indicating increased microbial phosphorus acquisition pressure at higher substitution rates. Fertilization significantly altered bacterial β-diversity at jointing, and dominant phyla correlated with plant and microbial stoichiometric ratios, suggesting community assembly driven by stoichiometry rather than soil nutrients alone. LEfSe identified distinct functional taxa enriched at different substitution rates, including carbon-degrading Singulisphaera under TF20 and nitrifying Nitrosomonadaceae under TF100, and these taxa were correlated with plant and microbial stoichiometry, linking microbial functional groups to nutrient cycling and yield. A moderate (20%) substitution rate therefore best reconciles yield maintenance with nutrient use efficiency, and the effects of organic fertilizer substitution on plant–soil–microbial stoichiometry and provides support for optimizing fertilization strategies.

Antibiotic resistance genes (ARGs) are becoming a global issue due to the emergence of superbugs. However, the impact of elevated CO₂ (eCO₂) on the soil antibiotic resistome remains largely unknown. Here, using a free-air CO₂ enrichment platform, we employed high-throughput quantitative PCR and 16S rRNA gene sequencing to investigate the effect of eCO₂ (ambient + 200 ppm) on soil ARGs and bacterial communities in a paddy ecosystem at harvest. The results showed that eCO₂ had no significant effect on rice biomass. A LEfSe analysis identified a clear taxonomic shift, with taxa such as c_Clostridia, g_Dehalobacter and g_Syntrophus being significantly enriched under eCO₂. The total relative abundance of ARGs increased 1.5-fold under eCO₂, driven by a 2.8-fold increase in multidrug resistance genes. The correlation and network analyses revealed that the proliferation of specific potential host bacteria was the primary driver of the observed ARG enrichment under eCO₂. Together, this study offers new insights into the eCO₂-driven alterations of soil antibiotic resistomes, highlighting the elevated dissemination potential of multidrug resistance genes within paddy ecosystems and their potential implications for food safety.