Effects of Different Plant and Row Spacing on Soil Chemical Properties, Microbial Communities, and Yield of Cold-Region Rice

Plant spacing and row configurations alter air circulation, light penetration and other conditions within the crop canopy, thereby affecting soil micro-environmental conditions. However, in cold-region rice cultivation, it remains unclear whether bacterial and fungal communities respond differentially to different planting configurations and how such microbial changes are associated with soil organic carbon fractions. This study conducted a two-year field experiment with three planting spacing treatments, including uniform row spacing of 30 cm × plant spacing of 12 cm (CK), (33 cm wide row + 17 cm narrow row) × plant spacing of 14 cm (A), and (33 cm wide row + 17 cm narrow row) × plant spacing of 12 cm (B). Soil samples were collected at the rice maturity stage in 2025 to evaluate treatment effects on soil chemical properties, microbial communities, and rice yield, and to explore the relationship between microbes and yield components. Results showed that treatments A and B significantly increased pH, soil organic carbon (SOC), readily oxidizable carbon (ROC), and water-soluble organic carbon (WSOC). Total nitrogen and available nitrogen levels significantly increased under treatment A but reduced under treatment B. In terms of microbial communities, treatments A and B enriched functional microbes involved in carbon and nitrogen cycling, while the community structures of both bacteria and fungi remained stable. Treatment A outperformed treatment B in enriching beneficial saprophytic fungi and suppressing pathogenic fungi. Compared with CK, treatments A and B increased yields by 7.37% and 2.64%, respectively, in the first year of the experiment and by 7.57% and 3.47%, respectively, in the second year of the experiment.