Contribution of particulate phosphorus to runoff phosphorus bioavailability

Area of Science:

• Environmental Chemistry
• Soil Science
• Eutrophication Studies

Background:

• Erosion-induced phosphorus (P) runoff contributes to water body eutrophication.
• The role of particulate phosphorus (PP) in eutrophication is not fully understood.
• Bioavailable P fractions in runoff from fine-textured soils require further investigation.

Purpose of the Study:

• To quantify bioavailable P fractions (dissolved molybdate-reactive phosphorus - DRP, desorbable PP - AER-PP, and redox-sensitive PP - BD-PP) in field runoff.
• To assess the significance of PP in the total P load contributing to eutrophication.
• To evaluate the influence of soil P status on P runoff dynamics.

Main Methods:

• Field sampling of surface runoff and drainflow from fine-textured Cryaquepts soils.
• Quantification of DRP, AER-PP (anion exchange resin-extraction), and BD-PP (bicarbonate-dithionite extraction).
• Derivation of annual PP losses using established relationships between PP and bioavailable forms.

Main Results:

• BD-PP losses in surface runoff were significantly higher (3-5 times) than DRP or AER-PP losses.
• Drainflow P losses were substantial, exceeding surface runoff losses at one site.
• Soil P status influenced DRP concentrations more than PP fractions, with moderate P soils showing greater reliance on PP runoff.

Conclusions:

• Particulate phosphorus, particularly BD-PP, is a major contributor to P runoff and eutrophication.
• Drainflow represents a significant P loss pathway, potentially greater than surface runoff.
• Management strategies should consider PP bioavailability and soil P status to mitigate eutrophication effectively.