Herbage responses and animal performance of nitrogen-fertilized grass and grass-legume grazing systems

Authors: PEREIRA NETO, JOSE - Auburn University; DUBEUX, JOSE - University Of Florida; DOS SANTOS, MERCIA - Federal Rural University Of Pernambuco; SANTOS, ERICK - University Of Alberta; DILORENZO, NICOLAS - University Of Florida; BRETAS, IGOR - University Of Florida; Jaramillo, David; RUIZ-MORENO, MARTIN - University Of Florida; QUEIROZ, LUANA - University Of Florida; TEMBE OUDOR, KENNETH - University Of Florida

Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2024
Publication Date: 2/27/2024
Citation: Pereira Neto, J., Dubeux, J., Dos Santos, M., Santos, E., Dilorenzo, N., Bretas, I., Jaramillo, D.M., Ruiz-Moreno, M., Queiroz, L., Tembe Oudor, K. 2024. Herbage responses and animal performance of nitrogen-fertilized grass and grass-legume grazing systems. Journal of Agricultural Science. https://doi.org/10.1017/S0021859624000182.
DOI: https://doi.org/10.1017/S0021859624000182

Interpretive Summary: Incorporating legumes into grass pasture systems represents a mechanism for the sustainable intensification of beef cattle production. This study evaluated herbage responses and animal performance of beef steers in contrasting grazing systems over two consecutive years. Treatments were three grazing systems: (1) N-fertilized bahiagrass in the summer and overseeded with a N-fertilized mixture of annual ryegrass and oat in the winter; (2) unfertilized bahiagrass in the summer, overseeded by a mixture of annual grass-clover in the winter; and (3) a mixture bahiagrass and rhizoma peanut, a perennial legume, during the summer, overseeded with annual grass-clover mixture in the winter. The results from this study indicate that 85% of the nitrogen fertilizer can be reduced when forage legumes are incorporated into grass-based pasture systems. This research will be of interest to livestock producers, researchers, and extension faculty interested in developing grazing systems with reduced nutrient inputs. Improving the productivity of pasture systems is valuable nutritionally for the animal, but will also improve the economic outcomes for livestock producers, resulting in more sustainable ruminant production systems.

Technical Abstract: Incorporating legumes into grass pasture systems represents a mechanism to sustainably intensify livestock production. This study evaluated herbage responses and animal performance of beef steers in contrasting grazing systems during 2 yr. Treatments were three grazing systems: (1) N-fertilized bahiagrass (Paspalum notatum Flügge) in the summer and overseeded with a N-fertilized mixture of annual ryegrass (Lolium multiflorum Lam.) and oat (Avena sativa L.) in the winter (GR+N); (2) unfertilized bahiagrass in the summer, overseeded by a mixture of annual grass-clover (Trifolium spp.) in the winter (GR+CL); and (3) a mixture of bahiagrass and Ecoturf rhizoma peanut (RP; Arachis glabrata Benth.) during the summer, overseeded with annual grass-clover mixture in the winter (GR+CL+RP). Annual N-fertilizer inputs were 224 kg N ha-1 yr-1 for GR+N and 34 kg N ha-1 yr-1 for GR+CL and GR+CL+RP. Average daily gain (ADG), gain per area (GPA), and stocking rate (SR) in the winter did not differ across treatments and averaged 0.87 kg d-1, 303 kg ha-1, and 2.72 AU ha-1 (1 AU = 350 kg), respectively. During the summer, GPA of GR+CL+RP was superior to GR+N and GR+CL, which were grass monocultures (257 vs. 129 kg ha-1, respectively), and SR averaged 3.19 AU ha-1 among treatments. The annual ADG and GPA, showed no significant difference among treatments, averaging 0.48 kg d-1 and 475 kg ha-1, respectively. Annual SR differed between treatments, where GR+N was greater (3.37 AU ha-1) than the other treatments, which averaged 2.76 AU ha-1. Integration of legumes into grazing systems in the summer and winter contributes to the development of sustainable grazing systems, reducing 85% of the N fertilizer application while maintaining livestock productivity.