MSc graduate defense seminar for LRIGS member, Kiah Leicht, Wednesday, January 17 at 1:30 pm, 802 General Services Building. “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.