Integrating forage legumes reduces dependence on N-fertilizer and increases the stability of grazing systems

Authors: TRUMPP, KEVIN - University Of Florida; DUBEUX, JOSE - University Of Florida; GARCIA, LIZA - University Of Florida; Jaramillo, David; PEREIRA, JOSE - Auburn University; SANTOS, ERICK - University Of Alberta; QUEIROZ, LUANA - University Of Florida; BRETAS, IGOR - University Of Florida; RUIZ-MORENO, MARTIN - University Of Florida; SOUZA, CLEBER - University Of Florida; SOLLENBERGER, LYNN - University Of Florida; DILORENZO, NICOLAS - University Of Florida; VENDRAMINI, JOAO - University Of Florida

Submitted to: European Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2025
Publication Date: 5/30/2025
Citation: Trumpp, K., Dubeux, J., Garcia, L., Jaramillo, D.M., Pereira, J., Santos, E., Queiroz, L., Bretas, I., Ruiz-Moreno, M., Souza, C., Sollenberger, L., Dilorenzo, N., Vendramini, J. 2025. Integrating forage legumes reduces dependence on N-fertilizer and increases the stability of grazing systems. European Journal of Agronomy. https://doi.org/10.1016/j.eja.2025.127708.
DOI: https://doi.org/10.1016/j.eja.2025.127708

Interpretive Summary: This project evaluated the long-term effects of including legumes into bahiagrass pastures, evaluating herbage responses, animal performance, and long-term system stability. The three systems were: 1) Grass+N which included nitrogen fertilized bahiagrass during summer, and overseeded with nitrogen-fertilized cereal rye and oat during winter; 2) Grass+Clover included bahiagrass without nitrogen fertilizer during summer, and it was overseeded with rye, oat, and a mixture of clovers during winter; and 3) Grass+Clover+RP included rhizoma peanut -bahiagrass mixture during summer, and it was overseeded with a similar rye-oat-clover mixture as for Grass+Clover. Including diverse legume species added a total of 140 kg nitrogen ha-1 yr-1 via biological nitrogen fixation. In addition, including rhizome peanut helped maintain animal performance similar to nitrogen fertilized grass systems. The results from this long-term experiment indicate that integrating forage legumes reduces dependence on nitrogen fertilizers, potentially improving the economic return and stability of a grazing system. This data is valuable for farmers and stakeholders, as it quantifies the long-term benefits of legume inclusion into grazed pasture systems.

Technical Abstract: Livestock systems are facing different challenges, including environmental degradation, food insecurity, and climate change. Thus, finding sustainable alternatives is imperative, and including N-fixing legumes in grazing systems presents a great opportunity. Rhizoma peanut - RP (Arachis glabrata Benth) is a warm-season legume with the potential to reduce industrial nitrogen (N) fertilizer inputs in tropical and subtropical regions. We evaluated the effects of different N fertilization levels and legume inclusions into bahiagrass (Paspalum notatum Flügge) pastures during the cool and warm season on herbage responses, animal performance, and long-term system stability. Including diverse legume species takes advantage of differential growth curves, both in the warm and cool seasons, adding a total of 139.1 kg N ha-1 yr-1 (66.5 kg N ha-1 during the cool season and 72.6 kg N ha-1 during the warm season) via biological N fixation (BNF). In addition, including RP helped maintain animal performance similar to N-fertilized grass systems. Yearly liveweight gain on Grass+N and Grass+RP systems averaged 635 and 626 kg ha-1, respectively, with the legume integration replacing 85% of N fertilizer inputs. The proportion of RP in feces was 49.5%, indicating the preference of grazing animals for this legume. The regression between the ADG (kg hd-1 d-1) and the fecal d13C (‰) helped predict the ADG using fecal samples. Additionally, the grass-legume mixture with RP was more stable than other grazing systems (P = .07). Greater stability was obtained by increasing the system biodiversity, where individual responses improved the overall system performance. In conclusion, integrating forage legumes reduced dependence on N fertilizers, potentially improving the economic return and stability of the system.