Department of Plant Sciences

On-farm field trials were conducted on sandy loam soils in Ontario and Quebec, Canada for three years to quantify N2O fluxes and cumulative N2O emissions as affected by the amount and timing of N fertilizer application to corn (Zea mays L.). Using the static chamber method, gas samples were collected and analyzed after preplant or sidedress N fertilization. In general, both N2O flux and total emission increased with the amount of N fertilizer applied at preplant or sidedress at the V6-V8 growth stage with peak flux rate from 30 to 900 μg N m-2 hr-1. Depending on N levels and timing of application, the cumulative emission ranged from 0.05 to 2.42 kg N ha-1 over the 28-d monitoring period, equivalent to 0.03 to 1.45% of the total N fertilizer applied. The amount and temporal distribution of rainfall played a major role in stimulating the rate of N2O emission. The flux of N2O was negligible when soil mineral N in the 0-15 cm layer was 15ºC, during early plant growth stages. Cumulative N2O emission was generally higher for sidedress incorporated N than preplant application probably because of higher soil water contents and temperatures later in the growing season induced higher rates of N2O production.