Phosphorus in waters from sewage sludge amended lysimeters

Area of Science:

• Environmental Science
• Soil Science
• Agronomy

Background:

• Phosphorus (P) concentrations above 0.05 mg/L in surface waters can lead to eutrophication.
• Anaerobically digested sewage sludge is increasingly used as a fertilizer amendment.
• Understanding phosphorus dynamics from sludge application is crucial for water quality management.

Purpose of the Study:

• To quantify total phosphorus (P) concentrations in runoff and tile drainage.
• To compare P losses from land treated with inorganic fertilizer versus sewage sludge.
• To assess the impact of sludge on soil P fractions.

Main Methods:

• Utilized instrumented, large-scale lysimeters planted with corn (Zea mays L.).
• Collected runoff and tile drainage water samples over two years.
• Analyzed soil samples for total P and various P fractions.

Main Results:

• Sewage sludge applications resulted in higher annual P losses in runoff and tile drainage compared to superphosphate fertilizer.
• Sludge applications did not significantly alter total soil organic P but decreased its percentage of total P.
• Soil P fractions associated with saloid, Al, Fe, and reductant-soluble P increased with sludge application.

Conclusions:

• Sewage sludge application can increase phosphorus export to surface waters, posing a risk of eutrophication.
• The form of P in soil changes with sludge application, with increased inorganic P fractions.
• Careful management of sludge application rates and timing is necessary to mitigate environmental impacts.