Soil characteristics and phosphorus level effect on phosphorus loss in runoff

Area of Science:

• Soil Science
• Environmental Science
• Agricultural Science

Background:

• Phosphorus (P) loss in agricultural runoff contributes to eutrophication and degrades water quality.
• Limited data exists on the specific relationships between soil phosphorus (P) and runoff P.

Purpose of the Study:

• Investigate the relationship between runoff dissolved reactive phosphorus (DRP) and soil P in three Oklahoma benchmark soils.
• Determine if these relationships are soil-specific.

Main Methods:

• Three Oklahoma soils were amended with diammonium phosphate to create a range of water-soluble phosphorus (WSP) and Mehlich-3 phosphorus (M3P).
• Simulated rainfall was applied to bare soil boxes, and runoff was collected and analyzed for DRP and total P.
• Soil samples were analyzed for M3P, WSP, and various P saturation indices (PSI(ox), PSI(WSP), P(sat)).

Main Results:

• Runoff DRP showed a strong correlation with M3P (r2 > 0.92) and WSP (r2 > 0.88) for individual soil series.
• Significant relationships were observed between DRP and P saturation indices.
• Regression slopes differed significantly among soil series, indicating soil-specific relationships.

Conclusions:

• The amount of DRP in runoff is highly dependent on soil P levels, specifically M3P and WSP.
• Phosphorus saturation indices are also significant predictors of DRP loss.
• Soil-specific characteristics significantly influence P runoff dynamics, necessitating tailored phosphorus management strategies.