Assessing Soil Functional Status Across An Agroecosystem Using Soil Phosphatase Enzymes.

Soil enzymes have been shown to be primary in the functional ecology of soil ecosystems.  These enzymes have also been associated with the biogeochemical cycling of carbon, nitrogen, and phosphorous in the ecosphere at large.  Because of the sensitivity of soil enzymes to changes in the environment, and their association with plant and microbial communities, their importance have been consistently suggested as ecological indicators within the soil system.  This study utilized a survey methodology in which 45 samples were taken from three distinct land use types (pine plantation, grazed pasture, and cultivated vegetable crops) across one agricultural landscape.  Soil organic carbon (SOC), pH, and phosphatase enzyme activities were measured and subjected to t-tests in order to determine significant differences between the means.  Results demonstrate that the forested and grazed pasture areas were most distinctive in measured soil properties. In the grazed pasture, soil alkaline phosphatase (3.21 µmol p-nitrophenol g soil^-1 hr^-1), phosphodiesterase (1.96 µmol p-nitrophenol g soil^-1 hr^-1), SOC (4.41%), TN (0.39%) were all at their highest value across the landscape.  The cultivated area was lowest in soil alkaline phosphatase (1.43 µmol p-nitrophenol g soil^-1 hr^-1) and SOC (2.70%). Soil pH was lowest in the forested area (4.90), which also had the lowest activity of phosphodiesterase (1.10 µmol p-nitrophenol g soil^-1 hr^-1).  Soil phosphatase enzymes correlated with soil organic carbon, and shows that phosphatase enzyme activity may be a good determinant in the ecological status of agricultural soils.