Kiah Leicht | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Kiah Leicht. This seminar is open to the general public to attend.

MSc with Drs. Robert Grant and Symon Mezbahuddin.

Thesis Topic: Development of a Comprehensive Nitrogen Budget to Increase Nitrogen Use Efficiency and Reduce Nitrogen Losses in Semi-Arid Southern Alberta

Abstract:

Synthetic nitrogen (N) fertilizer has increased crop yields, but low crop fertilizer nitrogen use efficiency (NUE) results in N losses which negatively impact human and environmental health. Process-based ecosystem models can generate low-cost and time-efficient estimates to compare multiple management options for associated agronomic recovery and N losses. The model “ecosys” was used to develop a comprehensive N budget to determine the fate of N at a site in semi-arid Southern Alberta as influenced by N source (urea vs ESN), N rate (0–120 kg N ha-1), irrigation vs dryland, and interannual climatic variability (2008–2011). A field dataset was used to test modelled outputs. Modelled results indicated that NUE was 27 to 107% (vs measured NUE of 8 to 59%), N2O-N emissions were 0.13 – 0.68 kg N ha-1 yr-1 (vs measured N2O-N emissions based on linear interpolations of 0.09 – 1.53 kg N ha-1 yr-1), NH3-N losses were 2.5 – 7.6 kg N ha-1 yr-1, subsurface N losses were 0 – 30.2 kg N ha-1 yr-1, surface N losses were 0 – 0.4 kg N ha-1 yr-1, and changes in residual soil NO3-N were -58 to 51 kg N ha-1 yr-1. Compared to conventional urea fertilizer, ESN did not improve modelled yields or reduce N losses, but optimal N rate applications allowed for reduced modelled N2O emissions, lower residual soil NO3-N, optimal yield gains and increased NUE. Irrigation reduced NH3 volatilization and N2O emissions in dry years by increasing soil water content and crop N uptake but increased subsurface N losses in wet years due to increased modelled drainage compared to the dryland site. The results from this research could provide a methodology for developing effective N management strategies which balance agronomic benefits with environmental impacts.