Effect of nitrogen fertilizer on greenhouse gas emissions in two willow clones (Salix miyabeana and S. dasyclados) in southern Ontario, Canada

Abstract

Short-rotation coppice (SRC) systems are effective for long-term carbon (C) sequestration, however nitrogen (N) fertilizer application can lead to greater soil-derived carbon dioxide (CO2) and nitrous oxide (N2O) emissions. A SRC system with two different willow clones [S. miyabeana (SX67), S. dasyclados (SV1)] was evaluated for CO2–C and N2O–N emissions, and soil chemical characteristics in a split-plot design with fertilized and unfertilized treatments in southern Ontario, Canada. Soil temperature and moisture, and photosynthetic photon flux density (PPFD) were also quantified. Mean CO2–C emissions from SV1 and SX67 ranged from 72 to 91 mg CO2–C m−2 h−1 in fertilized treatments, and from 63 to 105 mg CO2–C m−2 h−1 in unfertilized treatments. Carbon dioxide emissions from the SV1 clone was significantly lower (p = 0.0001) than that from the SX67 clone, but were strongly influenced by seasonal temperature and moisture variability and availability of C substrates. Nitrous oxide emissions, and NO3 − and NH4 + soil concentrations increased following fertilizer application. Mean N2O–N emissions from SV1 and SX67 from fertilized treatments ranged from 22 to 26 μg N2O–N m−2 h−1 and were significantly higher (p = 0.009) than emissions from unfertilized treatments ranging from 16 to 17 μg N2O–N m−2 h−1. Clone type did not significantly influence N2O–N emissions. Results indicated that N2O emissions were more strongly affected by inorganic N fertilizer application, than seasonal changes associated with soil moisture and temperature.