Abundant rainfalls modulate the impact of fertilizer application practices on nitrous oxide emissions during spring wheat growing season

Citation

Pattey, E., and Gaudnik, C., 2016. Abundant rainfalls modulate the impact of fertilizer application practices on nitrous oxide emissions during spring wheat growing season. American Society of Agronomy Annual Meeting Phoenix (AZ) 06-09 Nov 2016.

Plain language summary

Nitrous oxide is a greenhouse gas emitted from soil following nitrogen fertilizer application. The emissions of nitrous oxide are highly heterogeneous in cultivated fields and intermittent. Using a field scale measuring technique, the nitrous oxide emissions were measured continuously over four growing seasons in fields planted with spring wheat to evaluate the influence of nitrogen fertilization and of climate conditions. Over the four growing seasons, air and soil temperatures and cumulative rainfall were close to the climate normals. During the growing season, cumulative rainfall was relatively similar between years, whereas the cumulative N2O emissions ranged from 815 to 1474 g N2O-N ha−1. Most of the variations between growing season took place during the vegetative period, in response to rainfall distribution during the period. Early in the growing season when enhanced nitrous oxide emission were observed, 76 g N2O-N ha−1 was emitted for each 10 mm of rainfall. The influence of applying a reduce rate of nitrogen on the emission of nitrous oxide could disappear, because of the distribution of rainfall larger than 10 mm d-1 in the vegetative period.Given that nitrous oxide emissions over the growing season were more affected by the distribution of rainfall larger than 10 mm d-1 than by the cumulative seasonal rainfall or the reduction of the nitrogen application rate by 40%, mitigation strategies in regions where rainfall is projected to be more frequent and intense in the early part of the growing season should go beyond reducing the nitrogen application rate.

Abstract

The interannual and seasonal variations in N2O emissions in response to N management practices and climate variations were examined using micrometeorological fluxes measured in spring wheat fields in eastern Canada during four growing seasons. The common practice of urea application at ~77 kg N ha−1 was compared with alternative practices, either ammonium nitrate application or application of ~43 kg N ha−1. Although N2O emissions tended to increase with ammonium nitrate application in comparison with urea application, emissions were not significantly different, and thus the effect of N rate on N2O emissions was studied regardless of the form. Over the four growing seasons, air and soil temperatures and cumulative rainfall were close to the climate normals. During the growing season, cumulative rainfall was relatively similar between years, whereas cumulative N2O emissions ranged from 815 to 1474 g N2O-N ha−1. The variations in N2O emissions arose mainly from the vegetative period, owing to the possibilities of high N2O emissions following fertilization and abundant rainfall during tillering. In comparison with the whole growing season, N2O emissions during the tillering stage were 69%, 72%, 49%, and 62% from the common practices in 2001, 2003, 2005, and 2011, respectively, and 67%, 37%, and 55% from the alternative practices in 2001, 2005, and 2011, respectively. During the tillering stage, enhanced N2O emissions were strongly related to the associated rainfall amount, with 76 g N2O-N ha−1 emitted for each 10 mm of rainfall. Given that N2O emissions over the growing season were affected more by the distribution of abundant rainfall (>10 mm) than by the cumulative rainfall or the reduction of the N rate by 40%, mitigation strategies in regions where rainfall is projected to be more frequent and intense in the early part of the growing season should go beyond reducing the common N rates.

Publication date

2016-11-06