Using phosphorus concentration in the soil solution to predict phosphorus desorption to water

Area of Science:

• Environmental Science
• Soil Science
• Agricultural Chemistry

Background:

• Water eutrophication is a growing concern, necessitating the restriction of phosphorus (P) losses from agricultural soils.
• Developing reliable methods to predict P losses is essential for environmental management.

Purpose of the Study:

• To test the hypothesis that dissolved reactive phosphorus (DRP) released from soil is proportional to the DRP concentration in the soil solution, influenced by the solution-to-soil ratio (W).
• To evaluate the predictive capability of P1:1 (DRP in 1:1 soil-water extract) for P desorption in diverse agricultural soils.

Main Methods:

• Investigated P sorption-desorption curves using 12 European agricultural soils with excess P fertilization.
• Conducted laboratory experiments under near-static and turbulent conditions to study P desorption.
• Used the 1:1 soil-water extract (P1:1) as a proxy for soil solution DRP concentration.

Main Results:

• The amount of desorbed P correlated with P1:1 raised to a power that decreased with increasing solution-to-soil ratio (W).
• The power decreased from 0.7–0.9 at W=100 to 0.2–0.4 at W=10,000.
• P1:1 demonstrated higher predictive value for P desorption than Olsen P or the degree of soil saturation with phosphorus (DSSP) index.

Conclusions:

• The P1:1 method effectively predicts P desorption across a wide range of agricultural soils.
• This finding suggests P1:1 is a potentially valuable tool for assessing P loss risk, especially in areas with high soil diversity.