Can application of enhanced efficiency fertilizers at planting reduce N losses from grain corn production in Ontario?

Nitrogen is a key input for sustaining high crop yields, but fertilizer N uptake efficiency in crops is relatively low. Part of the applied N not taken up by crops is vulnerable to losses such as nitrate leaching and nitrous oxide emissions. The overall goal of this project is to determine how Right Time and Right Source practices for N fertilizer management affect nitrogen losses.

Nitrous oxide emissions were monitored continuously using micrometerological towers, with 12 observations per day. Nitrate losses will be assessed using soil solution samplers installed at a depth of 30 inches. Four plots, each ten acres in size, receive four different N fertilizer treatments: two applied pre-planting and two applied at the 6th leaf stage. At pre-plant, urea is applied with and without urease and nitrification inhibitors, and at the 6th leaf stage, urea-ammonium nitrate (UAN) is applied with or without urease inhibitor.

Preliminary results from the 2015 growing season showed that large pulses of nitrous oxide emission occurred with the first rainfall events following each of the applications. The plot with UAN applied at sidedress emitted about 5 lb/A of nitrous oxide-N from May through September, compared to about 3 lb/A for the other three treatments. The higher emission following sidedress was likely due to considerably higher rainfall and soil moisture than is typical for Ontario corn. Within-plot yield variability was also higher than expected, partially due to the high rainfall and partially due to a tile drain issue that was corrected in the fall. So far, this experiment has shown that 4R components of N fertilizer management need to account for weather. The experiment is continuing in 2016 and 2017.