Effects of Biochar on Soil Properties and Microbial Communities Under Different Nitrogen Fertilization Rates in a Facility Vegetable Field

ABSTRACT Background Biochar shows a positive effect on soil properties and indigenous microbial communities in farmland; meanwhile, long‐term effects of biochar on native soils are poorly understood. Aims This research aimed to dissect the inherent relationships between soil physicochemical properties and microorganisms following the application of biochar under different nitrogen fertilization rates. Methods Thus, a 2‐year field trial, including four different consecutive crops, was performed to investigate the effect of biochar amendment with nitrogen fertilizer addition on soil properties and microbial community. Results Biochar exerted a significant influence on soil pH, bulk density (BD), and soil organic matter (OM) content. The soil quality index area was not significantly affected by biochar and nitrogen fertilizer. Biochar application increased the total phospholipid fatty acid (PLFA) contents from 16.34–17.51 to 36.74–58.49 nmol g −1 , whereas bacterial, fungal, Gram‐negative bacterial, and Gram‐positive bacterial increased by 2.4–4.3, 2.1–3.9, 1.1–4.0, and 1.6–2.3‐folds, respectively. The Shannon–Weiner diversity index increased by 4.7%–26.4%, Simpson index increased by 13.3%–18.4%, whereas the Pielou index decreased 9.7%–22.4% with the biochar amendments. Partial least squares path modeling results revealed that biochar and nitrogen fertilizer indirectly influenced both soil PLFA contents and alpha diversity through their effects on OM contents, BD, and mineral nitrogen availability. Conclusions In conclusion, the 2‐year field trial shows that biochar amendment, combined with different nitrogen rates, significantly impacts soil properties. Notably, it enhances soil microbial PLFA contents and diversity, suggesting its potential for long‐term soil health improvement.