Overseeding aeschynomene and N fertilization effects on forage characteristics, N fixation, and N2O‐N emissions of bahiagrass pastures

Abstract Aeschynomene ( Aeschynomene americana L.) is a warm‐season annual legume forage used in tropical and subtropical regions; however, there is limited information on agronomic and environmental benefits of aeschynomene when overseeded into bahiagrass ( Paspalum notatum Flüggé) swards. The objective of this study was to evaluate the effects of overseeding aeschynomene or applying N fertilizer to existing bahiagrass on forage characteristics, atmospheric N fixation, and N 2 O‐N emissions. The study was conducted in Ona, FL, from April 2019 to March 2021. Treatments were the split‐plot arrangement of bahiagrass‐aeschynomene or bahiagrass monoculture (main plot) and N fertilization level (0 or 60 kg N ha −1 ; subplot), distributed in a randomized complete block design with four replicates. Nitrogen fixation was estimated in plots receiving no N fertilization. The static chamber technique was used to estimate N 2 O‐N emissions. Overseeding aeschynomene did not increase forage accumulation (mean = 1300 kg dry matter [DM] ha −1 harvest −1 ) or N 2 O emissions (mean = 15 g N 2 O‐N ha −1 per day), but increased forage crude protein (CP) concentration (from 98 to 108 g kg −1 ) when compared to bahiagrass monoculture. Nitrogen fertilization increased forage accumulation (from 1200 to 1400 kg DM ha −1 per harvest) but it did not affect aeschynomene N fixation (84% N derived from atmospheric fixation [Ndfa]). Nitrous oxide emissions had significant temporal variability across all treatments; however, there were no differences in accumulated N 2 O‐N emissions among treatments (mean = 2.4 kg N 2 O‐N ha −1 per year). Overseeding aeschynomene is an effective management practice to increase forage CP concentration in pastures without increasing N 2 O‐N emissions.