[Characteristics and influencing factors of soil nitrification potential in coastal salinized farmland]

Understanding the nitrification capacity of coastal saline farmland soils and its main drivers is of great significance to regulate soil nitrification and improve the utilization efficiency of nitrogen fertilization in farmland. Using a combination of field investigations and laboratory analyses, we examined farmland soil nitrification potential and soil physical, chemical, and biological properties in the coastal muddy tidal flat saline soil area (Dongying and Dongtai). We established the correlation between soil properties and soil nitrification potential with multiple stepwise regression analyses and structural equation modeling (SEM). The results showed that soil pH value was relatively stable and other soil properties and soil nitrification potential varied in coastal saline farmland. The soil nitrification potential ranged from 0.04 to 10.42 mg·kg^-1·d^-1 and decreased with the increases of soil salinization level. Soil nitrification potential had the strongest correlation with soil organic matter, cation exchange capacity, and Cl^-, with the correlation coefficient being 0.409, 0.397 and -0.337, respectively. The results of multiple stepwise regression analysis showed that Na⁺, silt, cation exchange capacity, and CO₃^2-+HCO₃^- were the main influencing factors of soil nitrification potential. The results from the SEM analysis suggested that Na⁺, silt, cation exchange capacity, and CO₃^2-+HCO₃^- directly affected soil nitrification potential, and soil organic matter, clay, Cl^- and SO₄^2- had indirect effects. In all, soil Na⁺ and cation exchange capacity were the two main factors affecting nitrification. Adjusting soil NaCl content and cation exchange capacity was an effective means of regulating soil nitrification.