Integrated Metagenomics and 15N Isotope Tracing Reveal the Mechanisms Through which the Nitrogen-Planting Density Interaction Impacts Rice Root Nitrogen Uptake Efficiency

Designing appropriate nitrogen (N) application rates and planting densities is crucial for ensuring high-yield and high-quality rice production. The effects of N fertilizer and planting density on the soil microbial community composition and abundance and on root N uptake mechanisms were investigated. In this study, high-nitrogen low-density (HNLD), medium-nitrogen medium-density (MNMD) and low-nitrogen high-density (LNHD) experiments were conducted via the bucket planting method, and plant physiology, dry matter mass and N uptake, root enzyme activities and rhizosphere soil microbial communities were examined via metagenomic sequencing and isotope tracing. The HNLD treatment exhibited the highest N absorption and utilization capacity. Compared to those in the other treatments, the δ15N values and abundance increased by 52.96–63.45