Decomposition and plant-available nitrogen in biosolids: laboratory studies, field studies, and computer simulation

Area of Science:

• Environmental Science
• Agronomy
• Soil Science

Background:

• Municipal biosolids are increasingly land-applied as fertilizer.
• Accurate estimation of plant-available nitrogen (PAN) from biosolids is crucial for sustainable agriculture.
• Biosolids decomposition rates and nutrient release vary depending on their properties and environmental conditions.

Purpose of the Study:

• To characterize the amount of plant-available nitrogen (PAN) released from land-applied municipal biosolids to agronomic crops.
• To compare observed PAN with predictions from a computer simulation model.
• To evaluate the influence of biosolids properties and storage treatments on nitrogen release.

Main Methods:

• Laboratory incubation studies of biosolids-soil mixtures to determine decomposition kinetics.
• Field studies to measure plant-available nitrogen (PAN) release under actual growing conditions.
• Computer simulation using the Decomposition model with laboratory and field data.

Main Results:

• Biosolids decomposition exhibited two phases (rapid and slow) with mean rate constants of 0.021 d⁻¹ and 0.0015 d⁻¹, respectively.
• Mean observed PAN was 18.9 kg N Mg⁻¹, representing 37% of the total biosolids nitrogen during the growing season.
• The Decomposition computer model accurately predicted observed PAN, with a mean prediction of 19.2 kg N Mg⁻¹.

Conclusions:

• Land application of municipal biosolids releases a significant portion of their total nitrogen as plant-available nitrogen (PAN).
• The Decomposition computer model, utilizing laboratory kinetics and field data, provides reliable estimates of PAN release.
• Stabilization by lagoon storage was the only treatment process found to influence biosolids decomposition rates.