Dataset on the long-term effects of nitrogen and phosphorus fertilization on soil phosphorus availability.

We examined the responses of bulk soil chemical properties, enzyme activities, microbial biomass, P fractions, and cycling indices to N and P fertilization in <i>Metasequoia glyptostroboides</i> plantations under a subtropical monsoon climate. The experiment spanned 10 years and included five levels of N (0, 56, 168, 280, 336 kg ha⁻¹) and P (0, 7.8, 31, 93, 155 kg ha⁻¹) fertilization. P fertilization resulted in stronger response of available P and inorganic P fractions, such as Resin-Pi, NaHCO₃-Pi, and NaOH-Pi, compared to N fertilization. Under N fertilization, available P was mainly influenced by microbial biomass P and carbon, with NaOH-Pi being its dominant sources of supply, while both the direct and indirect effects of N fertilization on available P were minimal. In contrast, , available P under P fertilization was regulated by total P, nitrate (NO₃⁻), and organic carbon contents, with NaOH-Pi, NaOH-Po, NaHCO₃-Pi, and NaHCO₃-Po as the dominant forms. The direct effects of P addition on available P, reflected by a pathway coefficient of 0.37, slightly exceeded its indirect effects.