Response of soil phoD phosphatase gene to long-term combined applications of chemical fertilizers and organic materials

The bacterial phoD gene encodes alkaline phosphatase (AlP), an enzyme which participates in the hydrolysis of organic phosphorus (P) in soils and is therefore important to the global P cycle. However, how phoD gene communities respond to long-term combined applications of chemical fertilizers and organic materials remains largely unknown. Accordingly, a long-term (25 years) experiment was performed to compare the effects of no treatment (Control) with chemical fertilizers (NPK), chemical fertilizers with corn straw (NPKS), and chemical fertilizers with swine manure (NPKM) on the phoD gene community using high-throughput sequencing. Relationships among AlP, P forms and other soil properties were also evaluated. The phoD gene abundance and diversity significantly decreased with chemical fertilizer alone or in combination with corn straw addition compared to the control, while a similar diversity and significant increased abundance was observed in chemical fertilizer with swine manure. The phoD gene community composition was distributed into three groups in a canonical correlation analysis (CCoA) plot and showed partially significant correlation with AlP. Our results indicate that the abundance and composition of the phoD gene community were significantly correlated with P reserves and P availability. Long-term fertilization reshaped the phoD community, with different members being influenced by different soil properties accompanied by various fertilizer treatments.