Nitrous oxide emissions from agricultural soils in southern Ontario: Influence of nitrogen fertilization and topography
Applying fertilizer N to agricultural soils in excess of crop requirements increases the potential of nitrous oxide (N2O) emissions. Developing methods to accurately predict and apply fertilizer N requirements is thus important. Nitrous oxide production was examined in a corn ('Zea mays ' L.) cropping system under five fertilizer N rates across three landscape positions. Corn yield response to applied fertilizer N varied with slope position and the responses were not the quadratic responses normally observed. It was not possible to calculate a most economic rate of N fertilization, however, both soil and vegetation data indicated that fertilizer N rates above 100 kg N ha-1 were in excess for all slope positions. N2O emissions were significantly influenced by N rate for periods 2 (July 2002) and 3 (August 2002) only. Fertilizer N rates above 0 kg N ha-1 in the upper slope position, above 100 kg N ha-1 in the mid-slope position, and above 50 kg N ha-1 in the lower slope position increased N2O emissions. Based on these observations site-specific fertilizer application would appear to have the potential to reduce N 2O emissions.