Quantification of pyrophosphate in soil solution by pyrophosphatase hydrolysis

A commercial pyrophosphatase from Saccharomyces cerevisiae selectively hydrolyzed sodium pyrophosphate, but showed no significant activity towards a range of other organic and condensed inorganic phosphorus compounds. Pyrophosphate determined by pyrophosphatase hydrolysis accounted for 38 ± 12% (mean ± standard error of 19 sites) of the non-reactive phosphorus in soil solution obtained by centrifugation from a series of lowland tropical rain forest soils. Pyrophosphate concentrations were up to 89 μg P l−1 and correlated positively with microbial phosphorus, soil solution pH, and native phosphomonoesterase activity in soil solution, but not with total soil pyrophosphate determined by NaOH–EDTA extraction and solution 31P NMR spectroscopy. In summary, we identify pyrophosphate as a major constituent of soil solution phosphorus in lowland tropical rain forests, and demonstrate that a commercial pyrophosphatase can be used as a selective tool to quantify trace concentrations of pyrophosphate in soil solution.