A denitrification bed is a system that can reduce the nitrate concentration in subsurface drainage water. There is a need to investigate the carbon quality of old woodchips to gain a better understanding of the effect of age on woodchip properties. The objectives of this study were to characterize the carbon quality and carbon to nitrogen (C/N) ratio of aged woodchips and to examine the suitability of a denitrification bed for a replicated experiment. To achieve these goals, we excavated four-year-old woodchips along the length of a 106.4 m long denitrification bed near Willmar, Minnesota, and analyzed them for particle size, C/N ratio, and carbon quality. Particle size analysis showed similarities from 12.5 to 106.4 m along the bed. We found a mean C/N ratio ranging from 58.4 3.17 to 153.4 9.57 (smallest at the inlet). The mean lignocellulose index (LCI, a measure of carbon quality) of the four-year-old woodchips ranged from 0.47 to 0.57 (highest at the inlet). The woodchip particle sizes, C/N ratios, and LCI from 25.9 to 106.4 m along the bed length were similar. In conclusion, the C/N ratio and LCI of the four-year-old woodchips showed effects of decomposition and increased woodchip carbon recalcitrance over time, respectively.
Bibliographical noteFunding Information:
We express gratitude to Edward Dorsey, Jacob Mattson, Brendan McShane, Scott Schumacher, and Todd Schu-macher for their assistance. Funding of this research was provided by Minnesota Discovery, Research and InnoVation Economy (MnDRIVE). The funding source was not involved in the study design, collection, analysis, interpretation of data, and preparation of the manuscript.
© 2018 American Society of Agricultural and Biological Engineers.
- Denitrifying bioreactor
- Tile drainage
- Water quality
- Woodchip bioreactor