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Phosphorus leaching in relation to soil type and soil phosphorus content
Faruk Djodjic1, Katarina Börling, Lars Bergström
1Department of Soil Sciences, Swedish University of Agricultural Sciences, Box 7072, S-750 07 Uppsala, Sweden. Faruk.Djodjic@mv.slu.se
Journal of Environmental Quality
|April 13, 2004
Summary
Phosphorus leaching from soils is a key driver of freshwater eutrophication. This study found soil P levels and sorption indices were poor predictors of P leaching, with water transport and subsoil properties being more critical factors.
Area of Science:
- Environmental Science
- Soil Science
- Agronomy
Background:
- Phosphorus (P) losses from agricultural soils contribute significantly to freshwater eutrophication.
- While surface runoff is a known P loss pathway, P leaching is increasingly recognized as a critical transport mechanism.
- Elevated soil P levels necessitate understanding the relationship between P leaching and soil P status.
Purpose of the Study:
- To investigate the relationship between soil phosphorus levels and actual phosphorus leaching.
- To identify key factors influencing phosphorus (P) leaching in different soil types.
- To evaluate the predictive power of soil test P and sorption indices for P leaching.
Main Methods:
- Undisturbed soil columns from a long-term Swedish fertility experiment were used to measure total phosphorus (TP) and dissolved reactive phosphorus (DRP) leaching over three years.
- Five different soil types with varying P fertilization histories were analyzed.
- Soil P concentrations (Olsen P, P-AL) and P sorption indices (PSI, P sorption saturation) were measured in the topsoil.
Main Results:
- Total P losses ranged from 0.03 to 1.09 kg ha(-1) yr(-1).
- No consistent correlation was found between topsoil P concentrations or sorption indices and P leaching.
- Water transport mechanisms and subsoil properties were identified as more influential than topsoil P levels for P leaching.
Conclusions:
- Site-specific factors, particularly water flow pathways and subsoil characteristics, are crucial indicators of P leaching potential.
- Topsoil phosphorus levels and standard soil tests are not reliable predictors of phosphorus leaching across all soil types.
- Understanding preferential flow paths is essential for predicting and mitigating phosphorus losses via leaching.