Nitrate in waters from sewage-sludge amended lysimeters

Area of Science:

• Environmental Science
• Agronomy
• Soil Science

Background:

• Agricultural practices impact water quality through nutrient runoff.
• Sewage sludge is a potential source of nutrients but can lead to environmental contamination.
• Nitrate nitrogen (NO3(-)-N) is a key pollutant in agricultural runoff and tile-drainage.

Purpose of the Study:

• To quantify nitrate nitrogen losses in runoff and tile-drainage from corn fields treated with sewage sludge and inorganic fertilizer.
• To compare the environmental impact of sewage sludge versus inorganic fertilizer on nitrogen leaching.
• To identify patterns in nitrate nitrogen loss based on application type and timing.

Main Methods:

• Utilized instrumented, large-scale lysimeters planted with corn (Zea mays L.).
• Applied sewage sludge at high rates (2292-3286 kg N ha-1) and inorganic fertilizer (336 kg N ha-1 year-1) over two years.
• Measured nitrate nitrogen concentrations and losses in runoff and tile-drainage water.

Main Results:

• Sewage sludge treatments exhibited substantially higher annual NO3(-)-N losses (371-663 kg ha-1) in tile-drainage compared to inorganic fertilizer (31-79 kg ha-1 year-1).
• Median NO3(-)-N concentrations in tile-drainage were significantly higher for sludge (148-223 mg L-1) than for inorganic fertilizer (24-44 mg L-1).
• Unaccounted for nitrogen losses were substantial, particularly for sludge treatments (1800-2400 kg ha-1 year-1).

Conclusions:

• High-rate sewage sludge application poses a significant risk of nitrate nitrogen pollution to water bodies via tile-drainage.
• Inorganic fertilizer, while causing losses, resulted in considerably lower nitrogen leaching compared to sewage sludge.
• Management strategies are needed to mitigate nitrogen losses from sludge-amended soils, especially concerning tile-drainage and timing of runoff events.