Authors

Abstract

The impact of interactions between management and climate on nitrous oxide (N2O), carbon dioxide (CO2), and ammonia (NH3) emissions are not well understood. This study quantified the effect of urea fertilizer application timing on inorganic N movement, immobilization, and the gaseous emissions of N2O-N, CO2 -C, and NH3-N. Urea was applied once, at two rates (0 and 224 kg ha(-1)) on six dates (early fall, 20 Sept. 2017; mid-fall, 11 Oct. 2017; early winter, 1 Nov. 2017; early spring, 1 May 2018; mid-spring, 22 May 2018; and early summer, 12 June 2018). Gaseous emissions, soil temperature, and soil moisture were measured every 4 h for 21 consecutive days following urea application. Changes in soil inorganic N contents were used to determine the amount of inorganic N remaining in the soil, nitrification, immobilization/fixation, and leaching. For all fertilizer application dates, the cumulative fertilizer derived N2O-N emissions for the 21 days following application were <0.05% of the applied N. Fertilizer-derived N2O-N emission rates were higher than N2O-N emission rates in the unfertilized soil in early fall and early summer. Even though the highest net N2O-N emissions occurred in early spring, the application of fertilizer did not increase emissions. The highest net N2O-N + NH3-N emissions occurred in cool soils (early spring) in soils with water filled pore space (>60%). These findings indicate that intergovernmental panel on climate change (IPCC) default value of 1% of applied N for N2O emissions improved by considering the fertilizer application date.