Relationship Between Phosphorus Forms and Phosphatase Activity in Soils Amended with Poultry Manure.

Up to 80% of the phosphorus (P) in poultry manure (PM) can be present in organic forms that require mineralization via phosphatase enzymes prior to plant utilization.   To determine the correlation between soil P distribution and phosphatase activity we sequentially extracted two Maine soils amended with poultry manure with H₂O, 0.5 M NaHCO₃, 0.1 M NaOH, and 1.0 M HCl at 0 (control), 100 (PM100), or 200 (PM200) mg manure P per kg soil during 108 days of aerobic incubation.  We determined activities of acid (AcPase, pH 6.5) and alkaline (AkPase, pH 11.0) phosphomonoesterase, and phosphodiesterase (PDase), and quantitated inorganic (P_i) and organic (P_o) P in each fraction.  Correlation between PDase and P fractions was not consistent between soils or treatments and was largely insignificant.  Significant positive correlations were found between both types of phosphomonoesterase and P_o in NaHCO₃- and NaOH-extracts in the low-indigenous P Newport soil with Control and PM100; however, there was no correlation with the high-indigenous P Caribou soil or when Newport soil was amended with PM200.  These observations suggest that P_o stimulates phosphomonoesterase activity when soil P levels are low but high P_i concentrations may inhibit activity or decouple this relationship.