EGU22-6437, updated on 28 Mar 2022
https://doi.org/10.5194/egusphere-egu22-6437
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Nitrogen dynamics of two contrasting soils amended with two types of municipal sewage sludge.

Georgios Giannopoulos, Athanasios Balidakis, Vasileios Tzanakakis, Nikolaos Monokrousos, and Ioannis Ipsilantis
Georgios Giannopoulos et al.
  • Aristotle University of Thessaloniki, School of Agriculture, Thessaloniki, Greece (george.z.giannopoulos@gmail.com)

Under the framework of Cyclic Economy and EU Green Deal, sewage sludge represents an ideal soil amendment with a potential to increase soil OM, provide nutrients and reduce chemical fertilization, which otherwise would be disposed in landfills. Nonetheless, its agronomic use comes with an uncertainty of its potential to release ample plant-available N and trace-metals in a wide range of soils.

This study investigated the N dynamics of municipal sewage sludge applied in two contrasting soils; an acidic (pH 5) and an alkaline (pH 8). Stabilized sewage sludge, limed (LM) or air-dried (AD), was applied (2% dw) in soil mesocosms (1500 g) that were incubated for 90 days (25oC; 12% soil moisture). A fertilized treatment (F: 100 mg/Kg NH4NO3), and a non-amended treatment (control) were also included. During the incubation soil NO3-, NH4+, N2O and CO2 were regularly monitored. Anaerobic mineralizable N (AMN) was determined at 15 days. At the end of the incubation, trace-metals, organic C and total Kjeldahl N were determined using standard methods.

The acidic soil receiving LM and AD sewage sludge had 4x and 5x greater (p=0.004) AMN rates than the control. Whereas the alkaline soil receiving air-dried sewage sludge had 2x greater (p=0.01) AMN rates than the control. Soil organic C was on average(±SE) 10.4±0.6 g/Kg and no significant differences were found in the acidic soil. In the alkaline soil, organic C was on average 16.1±0.4 g/Kg, and LM and AD treatments had significantly more org. C than the control (p=0.01). Total N was on average 1.5±0.3 g/Kg and no significant differences were found in both soils. During the incubation, soil NH4+ decreased in LM and AD treatments, and slightly increased in F and C treatments in the acidic soil. Soil NH4+ in the alkaline soil slightly increased for all treatments. A sharp increase in soil NO3- in the acidic soil was observed in all treatments except the control at approx. 60 d. In the alkaline soil, soil NO3- remained at similar levels as initially. It appears that in acidic soils receiving sewage sludge, the relative low soil pH inhibits NH4+ oxidation, whereas in alkaline soils the relative high pH inhibits NO3- reduction. Cumulative CO2 emissions were ~1.3x greater in LM and AD than F and control treatments, and cumulative N2O emissions were ~1.5x greater in AD only than F and control treatments for both soils. Interestingly, N2O emissions for LM were at similar levels to the control treatment for both soils. At the end of the incubation, trace-metal concentration increased in all treatments, yet, it remained below legislative critical levels. The above effects varied slightly between LM and AD sewage sludge, therefore further experimentation is required to understand the effects of sewage sludge type and quality on soil fertility and crop productivity. Our preliminary results show that stabilized sewage sludge has the potential to be a safe soil conditioner and fertilizer under the framework of Cyclic Economy and EU Green Deal.

Funding: The research work was supported in part by the Hellenic Foundation for Research and Innovation

How to cite: Giannopoulos, G., Balidakis, A., Tzanakakis, V., Monokrousos, N., and Ipsilantis, I.: Nitrogen dynamics of two contrasting soils amended with two types of municipal sewage sludge., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6437, https://doi.org/10.5194/egusphere-egu22-6437, 2022.