Fertilizer timing affects nitrous oxide, carbon dioxide, and ammonia emissions from soil

The impact of interactions between management and climate on nitrous oxide (N 2 O), carbon dioxide (CO 2 ), and ammonia (NH 3 ) 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 N 2 O‐N, CO 2 ‐C, and NH 3 ‐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 N 2 O‐N emissions for the 21 days following application were <0.05% of the applied N. Fertilizer‐derived N 2 O‐N emission rates were higher than N 2 O‐N emission rates in the unfertilized soil in early fall and early summer. Even though the highest net N 2 O‐N emissions occurred in early spring, the application of fertilizer did not increase emissions. The highest net N 2 O‐N + NH 3 ‐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 N 2 O emissions improved by considering the fertilizer application date.