High temporal resolution nitrous oxide fluxes from corn (Zea mays L.) in response to the combined use of nitrification and urease inhibitors

摘要

Environmental pollution caused by nitrous oxide (N2O) emission is a global concern because N2O is a potent greenhouse gas and contributes to ozone destruction. Agriculture is an important economic sector contributing to N2O emission worldwide, largely from agricultural soil and fertilizer induced emissions. Synchronizing nitrogen (N) fertilization with N plant demand has the potential to mitigate N2O emissions. This synchronization can be achieved through either delaying N fertilization until the crop reaches a developmental stage demanding the nutrient or by the use of nitrification and urease inhibitors (NUI). The aim of this research was to (i) evaluate the effect of conventional sources of N (urea or urea-ammonium-nitrate, UAN) on N2O emissions and corn yield, compared to the same fertilizers with NUI, (ii) to compare urea + NUI fertilization at planting vs. UAN fertilization at side-dress stage (higher risks of yield penalty), and, (iii) to determine if the responses are weather dependent. N2O flux was measured by a micrometeorological high-resolution method for each "package" of management practices. There was a trend for higher emissions in all 3 years for the UAN at side-dress stage compared to urea + NUI at planting and in one of the years, there was a yield penalty associated with the delayed N fertilization. NUI reduced annual N2O emissions in 2 of 3 years for fertilization at planting (urea), and 1 of 3 years for side-dress fertilization (UAN). We show that largest reductions in N2O emissions are based on NUI lowering of NO3- concentration at times of high WFPS in a very dynamic relationship determined by when rainfalls occur. This may explain why response to use of NUI has not been consistent in previous experiments due to the variable nature of rainfall timing. We were able to identify this response due to the high frequency measurements capturing the large temporal variability in N2O fluxes.