Long-Term Manure Application Alters phoC- and phoD-Harboring Bacterial Communities and Soil Phosphatase Activities in Acidic Soil.

Long-term manure fertilization changes soil phosphorus (P) availability and the microbial groups involved in organic P mineralization, but phoC- and phoD-harboring communities may respond differently. In this study, a ten-year continuous field experiment was performed with fertilization regimes: mineral NPK alone and NPK combined with 15, 30, or 45 Mg ha-1 year-1 fresh pig manure (NPKM1, NPKM2, and NPKM3). Overall, we found that soil pH rose from 4.07 under NPK to 5.24 under NPKM3, and available P increased from 57.4 to 398.6 mg kg-1. In addition, acid phosphatase (ACP) activity was higher under NPKM2 and NPKM3, whereas ALP increased significantly only under NPKM3. phoC gene abundance was highest under NPKM3, while phoD abundance increased progressively across the manure-containing treatments. Diversity and community composition responded differently for the two functional genes. phoC-harboring Cupriavidus dominated the phoC community and was positively associated with ACP activity, whereas Pleomorphomonas was positively associated with ALP. Exploratory association networks comprised 85 nodes and 246 edges for phoC and 201 nodes and 1093 edges for phoD; genus-resolved central OTUs were treated as putative network hubs rather than functional keystones. ACP correlated positively with phoC gene abundance (p = 0.003) and OTU richness (p < 0.001), while ALP correlated strongly with phoD gene abundance (p < 0.001). Overall, phoC- and phoD-harboring communities showed distinct responses to long-term fertilization regimes receiving manure, and those responses were associated with phosphatase activity without establishing direct causal pathways.