100268 Soil Carbon Dynamics and Aggregate Size Fractions of Legume- or Grass-N-Based Forage-Livestock Systems Defoliated By Grazing or Clipping.

Poster Number 339-1411

See more from this Division: C06 Forage and Grazinglands
See more from this Session: Forage and Grazinglands Poster I

Tuesday, November 8, 2016
Phoenix Convention Center North, Exhibit Hall CDE

Sabrina Saraiva Santana1, Liliane Severino da Silva2, Maristela de Oliveira Bauer3, Marta Moura Kohmann4, Mary Kimberly Mullenix5, Lynn E. Sollenberger4, Jose Carlos Batista Dubeux Jr.6 and Maria Lucia A. Silveira7, (1)Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, Brazil
(2)FL, University of Florida, GAINESVILLE, FL
(3)Engenharia Rural, Universidade Federal do Espirito Santo, Alegre, BRAZIL
(4)Agronomy Department, University of Florida, Gainesville, FL
(5)Department of Animal Sciences, Auburn University, Auburn, AL
(6)North Florida Research and Education Center, University of Florida, Marianna, FL
(7)Range Cattle Research and Education Center, University of Florida, Ona, FL
Abstract:
Defoliation management and grassland species composition can influence nutrient cycling and soil C dynamics. We hypothesized that grazing, instead of haying, and inclusion of legumes, versus grass-N systems, would increase soil C stocks. The objective of this study was to determine C and N soil pools in legume- and grass-based, year-round production systems that were defoliated either by grazing or haying during four years. The four treatments were replicated three times. The legume system included the warm-season perennial ‘Florigraze’ rhizoma peanut (RP, Arachis glabrata Benth.), and the grass-N system included ‘Tifton-85’ bermudagrass (BG, Cynodon spp.). Both were overseeded with the cool-season forages rye (Secale cereale) and ryegrass (Lolium multiflorum) during winter, with the legume system also including crimson (Trifolium incarnatum) and red clovers (T. pratense). Grass-N plots received 50 and 30 kg N ha-1 after each summer and winter defoliation event, respectively. After four complete cycles of the systems, soil was sampled from 0 to 10 cm depth, air dried, and sieved through a 2-mm screen. Subsamples were wet sieved to obtain three aggregate fractions: 1) 250 to 2000 µm, 2) 53 to 250 µm, and 3) < 53µm. Each aggregate size fraction was dried at 65°C and analyzed for C and N. Aggregate Fractions 1 and 2 were separated into light and heavy C fractions. Initial results show greater increase of soil organic carbon (SOC) in grass-N relative to legume-based systems. Grazed treatments also showed greater SOC and N increase compared with haying systems. Results support the conclusion that plant species and defoliation management influence soil C and N dynamics of grasslands.

See more from this Division: C06 Forage and Grazinglands
See more from this Session: Forage and Grazinglands Poster I