Biochar affects soil properties and greenhouse gas (GHG) emissions when used as an agricultural amendment. Using a field study, we quantified the effects of two different biochar treatments [3 t/ha poultry manure + 3 t ha(-1) biochar (MB); and 3 t ha(-1) poultry manure, 3 t ha(-1) biochar + 135 kg N ha(-1) (MNB)] compared to a non-biochar amended soil [6 t ha(-1) poultry manure + 135 kg N ha(-1) (MN)] on soil characteristics [organic carbon (SOC), nitrogen (N), C/N, pH, moisture and temperature], crop metrics and temporal variations in NH4+ -N, NO3- -N and GHG over 2 years. MNB and MB treatments had a significantly lower (p < 0.05) soil moisture (16-22%), temperature (1-4%) and NO3- -N (24-39%) concentration compared to MN. The C/N ratio was 12% greater (p < 0.05) in biochar amended soil compared to MN. Crop metrics were not significantly different (p < 0.05). In both years, CO2 missions were significantly different (p < 0.05) among seasons (spring, summer, autumn) within and between treatments. N2O emissions were significantly different (p < 0.05) among seasons, and was 20% greater in the MNB treatment, in year 2 only. GHG emissions significantly (p < 0.05) correlated to soil moisture, temperature and NH4+. Our results demonstrated that biochar combined with poultry manure and/or N fertilizer caused no negative effects on soil and crops relative to commercial farming practices (poultry manure + mineral N fertilizer). We found that biochar influenced carbon (C) and N transformations in the soil-plant-atmosphere system and caused seasonal changes in GHG emissions.