Effects of adding different types of nitrogen on soil phosphorus content and stoichiometric carbon, nitrogen, and phosphorus characteristics in meadow grassland

Deposition of atmospheric nitrogen (N), which includes inorganic and organic N sources, has become an important phenomenon causing global change and affecting the grassland soil phosphorus (P) cycle. To study effects of different types of N addition on the soil P cycle, a five-year N addition experiment was carried out in the meadow steppe in Inner Mongolia. The inorganic (IN) to organic (ON) nitrogen ratios examined were 10 ꞉ 0 (N₁), 7 ꞉ 3 (N₂), 5 ꞉ 5 (N₃), 3 ꞉ 7 (N₄), 0 ꞉ 10 (N₅) and 0 ꞉ 0 (CK). By combining determination of soil available P content, total P content, and acid phosphatase activity with ecological chemometrics, this study explored the effects of different types of N addition on P content and stoichiometric characteristics in different soil layers of a meadow grassland. The results indicate that addition of different N types exerted no significant effect on soil total P content or acid phosphatase activity. The available P content in 0-10 cm topsoil under N₂ treatment was significantly higher than that of control soil and soil receiving other N addition treatments. Soil C/N, C/P, and N/P were not affected by the type of added N. The average topsoil C/N, C/P, and N/P values in 0-10 cm topsoil are lower than the national average level, necessitating follow-up research spanning a longer time scale.