Investigating the Influence of Irrigation Scheduling Practices on N2O Emissions Using the DNDC Model.

Investigating the influence of irrigation scheduling practices on N2O emissions using the DNDC model Jannatul Ferdous1, Warren Helgason2, and Reynald Lemke3 1Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, email: jannatul.ferdous@usask.ca 2Department of Civil and Geological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5A9, email: warren.helgason@usask.ca 3Saskatoon Research Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, S7N 5A8, email: reynald.lemke@agr.gc.ca Denitrification-Decomposition (DNDC) is a well-known robust process-based model for simulating nitrous oxide (N2O) emissions from agricultural soils. This model has been extensively used to explore N2O emissions under various fertilizer and tillage practices; however, it has not been used to explore the impact of irrigation scheduling practices. As soil moisture is one of the most important driving factors of N2O emissions, we used the DNDC model to investigate whether improved irrigation management practices are a viable greenhouse gas (GHG) mitigation technique for the Canadian Prairies. The model was first tested under local conditions by instrumenting two adjacent fields located near Saskatoon, Saskatchewan, Canada during the 2012 and 2013 growing seasons. Soil GHG emissions were manually sampled using static vented chambers, and were complemented by automated measurements of soil moisture, soil temperature, and local meteorological variables. The model was validated by comparing the simulated N2O emissions, soil temperature, and soil moisture with field observations, confirming that the model is suitable to use in this application. Subsequently, the model was used in scenario mode, in which various irrigation treatments were imposed. These included varying the irrigation depth per application, varying the timing of application, and varying the total seasonal amount of water applied. Interactions with soil nutrient status were evaluated by altering the timing of fertilizer application to coincide near irrigation events. The results from this research will show how N2O emission is influenced by irrigation management practices, and will help identify irrigation scheduling practices that can be used to mitigate GHG emissions.