Soil and colloidal phosphorus dynamics in three ky soils: bioavailability, transport and water quality implications
Date Issued
2003
Author(s)
Abstract
Particulate P constitutes a significant portion of the total P found in surface
runoff water. Water dispersed P-containing particles can travel long distances via
surface runoff and reach water bodies causing decrease in water quality. The main
objective of the study was to evaluate the potential facilitation of P transport by the
water dispersed soil colloids (WDC) using three KY soils with a long-term record of
poultry manure, and fertilizer P applications. Sequential fractionation for both whole
soils and colloidal samples revealed that the WDC had a greater total and labile P
content than the soil as a whole. Also, application of manure and fertilizer P seemed to
decrease colloidal organic P fractions and increase the inorganic P fractions over the
period of a growing season (May to September). Laboratory settling kinetics
experiments were set up for the clay-colloidal fractions of the soils. It was shown that
particulate P fractions paralleled WDC settling kinetics whereas dissolved P fractions
remained in solution even after 36 hours. Field taken intact soil cores were leached
with colloidal suspensions to test the effect of WDC on the vertical P movement.
Results illustrated the preferential flow of particulate P though the macropores. When
water was applied to the manure amended soil, dissolved P levels increased
significantly over the control. WDC additions lowered dissolved P levels to the
manure-amended columns, by sorbing to the WDC particles, but still greater than the
dissolved P levels of the columns that had not been applied with manure.
runoff water. Water dispersed P-containing particles can travel long distances via
surface runoff and reach water bodies causing decrease in water quality. The main
objective of the study was to evaluate the potential facilitation of P transport by the
water dispersed soil colloids (WDC) using three KY soils with a long-term record of
poultry manure, and fertilizer P applications. Sequential fractionation for both whole
soils and colloidal samples revealed that the WDC had a greater total and labile P
content than the soil as a whole. Also, application of manure and fertilizer P seemed to
decrease colloidal organic P fractions and increase the inorganic P fractions over the
period of a growing season (May to September). Laboratory settling kinetics
experiments were set up for the clay-colloidal fractions of the soils. It was shown that
particulate P fractions paralleled WDC settling kinetics whereas dissolved P fractions
remained in solution even after 36 hours. Field taken intact soil cores were leached
with colloidal suspensions to test the effect of WDC on the vertical P movement.
Results illustrated the preferential flow of particulate P though the macropores. When
water was applied to the manure amended soil, dissolved P levels increased
significantly over the control. WDC additions lowered dissolved P levels to the
manure-amended columns, by sorbing to the WDC particles, but still greater than the
dissolved P levels of the columns that had not been applied with manure.
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