Doctoral Dissertations

Date of Award

8-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Natural Resources

Major Professor

Patrick D. Keyser

Committee Members

J. Travis Mulliniks, Renata Nave Oakes, John M. Zobel

Abstract

Cool-season annual (CSA) grass and legume species, as well as warm-season forbs, can enhance established native warm-season grass (NWSG) pastures by extending the grazing season, reducing supplemental feed costs, suppressing weeds, increasing herbage production and overall forage quality, and increasing food and cover resources for pollinators and wildlife. Therefore, two NWSG experiments were conducted near Spring Hill, TN, 2018-2020, to assess three CSA seeding options (cereal rye monoculture, a cereal rye, ‘Purple Top’ turnip, ‘Trophy’ rape, ‘Frosty’ berseem clover, and ‘Dixie’ crimson clover polyculture, or non-planted control) and two warm-season N rates (0 or 67 kg N ha-1) on established switchgrass (SG) and big bluestem/indiangrass (BBIG) pastures. Switchgrass and BBIG plant density were not influenced by CSA seeding but varied by Year (P < 0.001). Plant density for BBIG was lower in 2020 than 2018 (23.6 vs. 29.1 plants m-2, respectively), whereas SG plant density was similar for 2018 and 2020 (15.0 and 14.0 plants m-2, respectively). Hay yield for both SG and BBIG varied among harvests (July 2019, July 2020, and September 2020; P < 0.001) but not by CSA seeding. Additionally, two other NWSG experiments were conducted near Greeneville, TN, 2017-2020, to assess the effect of within-season rest on the persistence of 11 native forbs when interseeded into established SG and BBIG pastures. Within-season rest treatment was not influential for total forb plant density or NWSG tiller density thus indicating persistence of forbs may not require within-season rest. Purple prairie clover never established while Illinois bundleflower was only observed flowering once despite having the greatest seeding rate among the forbs. Of the 11-species in the current mixture, interseeding a 6-species polyculture of black-eyed susan, Dixie ticktrefoil, lanceleaf coreopsis, Maximilian sunflower, oxeye sunflower, and purple coneflower could allow for plant biodiversity while offering floral resources for pollinators during the NWSG grazing season. Because CSA and native forbs did not affect plant density over the course of these experiments, incorporating CSA or native forbs may be a viable option for increasing grazing opportunities and forage production in NWSG pastures.

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