Effects of nitrogen forms on growth and soil bacterial diversity of Cinnamomum camphora ct. citral seedlings

The scarcity of natural citral has spurred interest in its alternative sources such as the essential oil-rich branches and leaves of citral balsam fir. This study assessed the impact of nitrate, ammonium, and amide nitrogen forms at varying concentrations on the growth, development, and soil bacterial diversity of 1-year-old Cinnamomum camphora ct. citral seedlings. Chemical approaches were employed to measure growth and development, and 16S rDNA high-throughput sequencing was utilized to analyze the soil bacterial diversity. Results demonstrated significant enhancements in plant height, ground diameter, and biomass accumulation with amide nitrogen. Nitrogen treatments also augmented leaf chlorophyll content and photosynthetic rates, particularly evident with 6 g/plant ammonium nitrogen. Amide nitrogen treatments exhibited significant increases in leaf nitrogen content. Nitrogen form profoundly influenced soil bacterial diversity, with nitrate and ammonium nitrogen fostering greater diversity and abundance compared to amide nitrogen. Predominant bacterial taxa, including Proteobacteria, Acidobacteria, Actinobacteria, Gemmatimonadetes, and Chloroflexi, exhibit varied responses to nitrogen forms. Functional predictions elucidated chemoenergetic heterotrophy, ammonia oxidation, and nitrification as key bacterial pathways. Correlations indicated positive associations of Proteobacteria with plant growth, while Acidobacteria and Actinobacteria display negative links with specific leaf traits. This study suggests valuable insights into optimized nitrogen fertilization strategies for successful C. camphora ct. citral cultivation, addressing market demands while considering soil microbial dynamics.