DISTRIBUTION AND STABILITY OF PYROPHOSPHATASE IN SOILS

Pyrophosphatase activity in soils is concentrated in surface soils and decreases with depth. Statistical analysis indicates that the activity of this enzyme is correlated with organic C in surface soils and in soil profiles. Pyrophosphatase activity is also correlated with the percentage clay and with the mole fraction of Mg/(Mg + Ca) in water extract of 18 surface soils examined. It is significantly but negatively correlated with percentage CaCO3 equivalent in surface soils. Storage of field-moist samples for 2 months at 5°C is a satisfactory method for preserving soil samples for assay of this enzyme in soils. Air-drying of field-moist samples results in decreases in pyrophosphatase activity ranging from 23 to 41% (av 35%). Heating field-moist and air-dried samples for 1 h before assay of activity showed that Pyrophosphatase is inactivated at temperatures above 60°C. © 1979.