Abstract Mountain hay meadows are a high‐elevation forage‐producing agroecosystem dependent on flood irrigation and nitrogen (N) fertilization to maintain yields, meaning management has great potential to influence greenhouse gas (GHG) emissions. To assess GHG fluxes and inorganic N dynamics in meadows, field monitoring was established at four ranches in Wyoming and Colorado for 24 months from October 2021 through September 2023. At each ranch, three long‐term management systems were compared: unirrigated rangeland, irrigated‐unfertilized meadow, and irrigated‐fertilized meadow. Soil carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) fluxes were measured along with soil samples (0‐ to 10‐cm depth) analyzed for water content, nitrate (NO 3 − ), and ammonium (NH 4 + ). Flood irrigation resulted in 41%–91% increase in annual CO 2 emissions compared to rangelands. Flood irrigation combined with fertilization increased CO 2 emissions by another 19% in 2023. Both irrigated‐fertilized and irrigated‐unfertilized meadows emitted CH 4 during flooding, while rangeland soils assimilated CH 4 throughout the study. Unexpectedly, N 2 O emissions were highest in rangelands and not influenced by irrigation or fertilization in meadows. Soil NO 3 − and NH 4 + concentrations were low during the growing season and no correlation between inorganic N and N 2 O emissions was observed. Calculated global warming potential in meadows revealed GHG emissions were driven mainly by CO 2 , indicating that maintaining photosynthetic carbon (C) sequestration in meadows through optimum agronomic management may be an important strategy to balance GHG emissions.
Adamson et al. (Thu,) studied this question.