Herbage responses and nitrogen agronomic efficiency of bermudagrass-legume mixtures

Authors: SANTOS, ERICK - University Of Florida; DUBEUX, JOSE - University Of Florida; MACKOWIAK, CHERYL - University Of Florida; BLOUNT, ANN - University Of Florida; SOLLENBERGER, LYNN - University Of Florida; Jaramillo, David; GARCIA, LIZA - University Of Florida; ABREU, DACIELE - University Of Florida; SOUZA, RAYANNE - University Of Florida; RUIZ-MORENO, MARTIN - University Of Florida

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2021
Publication Date: 5/10/2021
Citation: Santos, E., Dubeux, J., Mackowiak, C., Blount, A., Sollenberger, L., Jaramillo, D.M., Garcia, L., Abreu, D., Souza, R., Ruiz-Moreno, M. 2021. Herbage responses and nitrogen agronomic efficiency of bermudagrass-legume mixtures. Crop Science. https://doi.org/10.1002/csc2.20552.
DOI: https://doi.org/10.1002/csc2.20552

Interpretive Summary: Bermudagrass (Cynodon spp.) is an important warm-season grass for livestock in the southern USA. To be productive bermudagrass requires supplementary nitrogen (N). This two-year study assessed whether N fertilization could be halved by introducing alfalfa (Medicago sativa L.) or rhizoma peanut (RP; Arachis glabrata Benth.) into ‘Tifton-85’ bermudagrass monocultures without compromising productivity. Treatments were: bermudagrass, N-fertilized bermudagrass, alfalfa (‘Alfagraze 600 RR’), RP (‘Florigraze’), and the mixtures bermudagrass-alfalfa and bermudagrass-RP. Mixtures were fertilized with 45 kg N ha–1 harvest–1, whereas N-fertilized bermudagrass received 90 kg N ha–1 harvest–1. Seven harvests were made each year. N-fertilized bermudagrass and mixtures had similar total herbage accumulation (HA) in 2017, but mixtures produced approximately 3340 kg DM ha–1 yr–1 less than N-fertilized bermudagrass in 2016, which had a drier summer. Percentage of alfalfa in the mixtures decreased from 68 to < 1% by the end of the study. Rhizoma peanut proportion in mixtures was often low (max. 8%). N-fertilized bermudagrass had the greatest total harvested N in May of 2016 (96 kg N ha–1), but it did not differ from bermudagrass-RP in May of 2017. Nitrogen agronomic efficiency (NAE) was greater for mixtures (27.5 kg DM kg–1 N applied) than for N-fertilized bermudagrass (21 kg DM kg–1 N applied). Greater NAE in mixtures occurred due to limited response to high N fertilization rates in the N-fertilized bermudagrass. Further studies on establishment methods, cultivar selection, and management practices are still needed to adopt a successful bermudagrass-legume mixture in north FL.

Technical Abstract: Bermudagrass (Cynodon spp.) is an important warm-season grass for livestock in the southern USA. To be productive bermudagrass requires supplementary nitrogen (N). This two-year study assessed whether N fertilization could be halved by introducing alfalfa (Medicago sativa L.) or rhizoma peanut (RP; Arachis glabrata Benth.) into ‘Tifton-85’ bermudagrass monocultures without compromising productivity. Treatments were: bermudagrass, N-fertilized bermudagrass, alfalfa (‘Alfagraze 600 RR’), RP (‘Florigraze’), and the mixtures bermudagrass-alfalfa and bermudagrass-RP. Mixtures were fertilized with 45 kg N ha–1 harvest–1, whereas N-fertilized bermudagrass received 90 kg N ha–1 harvest–1. Seven harvests were made each year. N-fertilized bermudagrass and mixtures had similar total herbage accumulation (HA) in 2017, but mixtures produced approximately 3340 kg DM ha–1 yr–1 less than N-fertilized bermudagrass in 2016, which had a drier summer. Percentage of alfalfa in the mixtures decreased from 68 to < 1% by the end of the study. Rhizoma peanut proportion in mixtures was often low (max. 8%). N-fertilized bermudagrass had the greatest total harvested N in May of 2016 (96 kg N ha–1), but it did not differ from bermudagrass-RP in May of 2017. Nitrogen agronomic efficiency (NAE) was greater for mixtures (27.5 kg DM kg–1 N applied) than for N-fertilized bermudagrass (21 kg DM kg–1 N applied). Greater NAE in mixtures occurred due to limited response to high N fertilization rates in the N-fertilized bermudagrass. Further studies on establishment methods, cultivar selection, and management practices are still needed to adopt a successful bermudagrass-legume mixture in north FL.