Biochar can restrict N2O emissions and the risk of nitrogen leaching from an agricultural soil during the freeze-thaw period

Authors

• Riitta Kettunen Department of Biology, University of Eastern Finland, Box 111, FI-80101, Joensuu, Finland
• Sanna Saarnio Department of Biology, University of Eastern Finland , Box 111, FI-80101, Joensuu, Finland; Finnish Environment Institute, Box 111, FI-80101, Joensuu, Finland

DOI: https://doi.org/10.23986/afsci.7887

Keywords:

ammonium, leachate, N2O efflux, nitrate, freeze-thaw

Abstract

Freeze-thaw (FT) events in soils can cause a burst of nitrous oxide (N2O) and enhance N leaching during the spring-thaw event. We studied whether a soil amended with wood-derived (spruce chips) biochar (10 tonnes ha-1), produced at rather low temperatures (400-450°C), could reduce the burst of N2O and the risk of N leaching from an agricultural soil after a FT event. A short-term laboratory experiment (4 weeks) was conducted with 24 vegetated (Phleum pratense) mesocosms (12 controls, 12 biochar-treated) that had spent a dormant season in the dark at 15°C for two months after the growing season. N2O efflux to the atmosphere and ammonium (NH4+-N) and nitrate (NO3-N) in the percolated soil water were monitored before and after the FT event. N2O was monitored with the dark chamber method and analyzed using a gas chromatograph. We found that soil amended biochar can significantly diminish the burst of N2O after the soil FT event (by 61% just after FT event) and substantially reduce the risk of NO3-N and NH4+-N leaching from the agricultural soil. Compared to the control, the decrement in concentrations of NO3-N and NH4+-N in water percolated through the biochar amended soil in the mesocosms was 58% and 22%, respectively.