『Abstract
There is considerable concern about pollution of surface waters
with P. Although most of the research has focused on inorganic
P in surface runoff, it has recently become possible to easily
follow the fate of soluble organic P forms in soils and waters.
Two experiments were performed to compare the relative mobility
and soil fixation affinity of orthophosphate monoesters, orthophosphate
diesters, and soluble inorganic P. we used three P substrates,
4-methylumbelliferyl phosphate (MUP), deoxyribonucleic acid (DNA),
and KH2PO4 in (i) a
soil column experiment and (ii) a soil P adsorption test tube
experiment. Shortly after columns were prepared, approximately
two pore volumes of 0.005 M CaCl2 were passed
through 25 cm length columns containing 10 cm of loamy sand amended
with approximately 10 mg P as MUP, DNA, or KH2PO4 above 15 cm of nonamended loamy sand. The total
net quality of 757.8 μg P 2L-1 of orthophosphate diesters
in the leachate from the DNA columns exceeded the net quantity
of orthophosphate monoesters in leachate from the MUP column (4.6
μg P 2L-1) and soluble inorganic P from the KH2PO4 columns (34.0 μg P 2L-1).
Adsorption of soluble organic and inorganic P in the test tube
experiment yielded similar results: DNA, containing orthophosphate
diesters, had a relatively low affinity for soils. In both experiments,
high concentrations of other P compounds were identified in samples
treated with organic P substrates, suggesting enzymatic hydrolysis
by native soil phosphatase enzymes. These findings indicate that
repeated application of organic forms of P could lead to significant
leaching of P to ground water.』
(Introduction)
Materials and methods
Experiment I: Soil columns
Experiment II: Soil phosphorus adsorption in test tubes
Enzyme assay and phosphorus analysis
Statistical analysis
Results and discussion
Experiment I: Organic and inorganic phosphorus in soil column
leachate
Experiment II: Organic and inorganic phosphorus adsorption-desorption
Conclusions
Acknowledgments
References