Does splitting the nitrogen rate for corn (Zea mays) reduce the carbon dioxide equivalence?

Abstract

Splitting N fertilizer application between the corn (Zea mays) plants pre-emergence and vegetative growth stage has the potential to reduce N losses while increasing N use efficiency. However, there are few published reports that show that splitting fertilizer reduces greenhouse gas emissions. Therefore, this study compared the CO_2e (carbon dioxide equivalent) calculated from N₂O-N and CO₂-C emissions from a single pre-emergence application of 157 kg urea- N ha⁻¹ with a nonfertilized control and two applications of 78.5 kg urea-N ha⁻¹ that were applied at pre-emergence and at the corn plants V6 growth stage. Over three growing seasons (2021, 2022, and 2023), soil temperature, moisture, N₂O-N and CO₂-C emissions were measured six times per day from when the urea was applied to harvest. N₂O-N and CO₂-C emissions were separated into pre-split and post-split periods, and carbon dioxide equivalence was calculated. Splitting the N rate: (1) increased N₂O-N emissions in 2021 and 2022; (2) reduced CO₂-C emissions during the post-split period in 2022 and 2023; and (3) did not influence total CO_2e in 2021 and reduced CO_2e emissions in 2022 and 2023. Based on these results, splitting the N fertilizer rate between pre-emergence and the corn plants V6 growth stage should be considered as a potential climate smart practice.