Nitrogen transformation from three soil organic amendments in a sandy soil

Abstract

A sandy soil was amended with various rates (20 – 320 g air-dry weight basis of the amendments per kg of air-dry soil) of chicken manure (CM), sewage sludge (SS), and incinerated sewage sludge (ISS) and incubated for 100 days in a greenhouse at 15% (wt/wt) soil water content. At the beginning of incubation, NH₄-N concentrations varied from 50 – 280 mg kg⁻¹ in the CM amended soil with negligible amounts of NO₃-N. Subsequently, the concentration of NH₄-N decreased while that of NO₃-N increased rapidly. In soil amended with SS at 20 – 80 g kg⁻¹ rates, the NO₃-N concentration increased sharply during the first 20 days, followed by a slow rate of increase over the rest of the incubation period. However, at a 160 g kg⁻¹ SS rate, there were three distinct phases of NO₃-N release which lasted for160 days. In the ISS amended soil, the nitrification process was completed during the initial 30 days, and the concentrations of NH₄-N and NO₃-N were lower than those for the other treatments. The mineralized N across different rates accounted for 20 – 36%, 16 – 40%, and 26 – 50% of the total N applied as CM, SS, and ISS, respectively.

Keywords:

• Nitrogen mineralization
• sewage sludge
• chicken manure
• incinerated sewage sludge
• nitrogen immobilization

Acknowledgements

We appreciate the assistance of Tami Baugh, Bill Boge, and Melanie Wilson during the course of this experiment and preparation of the manuscript.