Nano-zeolite-coupled biochar-based phosphorus fertilizer enhances soil phosphorus availability and leaf phosphorus...

Phosphorus (P) availability is a major constraint on nutrient management in acidic Moso bamboo (Phyllostachys edulis) forests, where conventional P fertilizers are prone to rapid fixation by soil minerals. Biochar-based P fertilizers can help retain P in soil. Yet it is still unclear whether they can sustain soil P availability and support plant P nutrition over time in acidic forest soils.

Here, we carried out a 24-month field trial in a subtropical Moso bamboo forest. We compared three P fertilizer treatments: conventional phosphorus fertilizer (CP), biochar-based phosphorus fertilizer (BP), and nano-zeolite-coupled biochar-based phosphorus fertilizer (NBP). Soil P fractions, microbial biomass P, and leaf P concentration were investigated.

Compared with the CP treatment, the BP and NBP treatments increased soil pH and retained more P in labile and moderately labile pools. The NBP treatment exhibited the strongest positive effects on soil P availability, particularly after 24 months. At this time, NBP reduced the accumulation of HCl-P_i, a relatively poorly available inorganic P fraction, while maintaining more P in accessible forms, including H₂O-P_i, NaHCO₃-P_i, NaHCO_3-P_o, and NaOH-P_i. Beyond these physicochemical changes, NBP also enhanced biological P cycling, as indicated by increased microbial biomass P, phoD gene abundance, alkaline phosphatase activity, and leaf P concentration. These results suggest that NBP improved P supply through both microbial P retention and organic P mineralization. Overall, the nano-zeolite coupling enhanced the capacity of biochar-based P fertilizer to alleviate soil acidity and sustain P availability through these combined physicochemical and biological processes. The results obtained in this study reveal that NBP is a promising strategy for improving soil P availability and sustaining P nutrition in acidic Moso bamboo forest soils.