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

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 mu g N2O-N m(-2) h(-1) and were significantly higher (p = 0.009) than emissions from unfertilized treatments ranging from 16 to 17 mu g 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.