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Research Projects: Forage


At The University of Tennessee Institute of Agriculture projects related to forages with management practices, fertilization, species selection, economics, pest management, and disease control are presented here to highlight the accomplishments of our researchers.

Publications and Reports


Link Pointer Comparison of Alfalfa Mixed with Tall Fescue and Bermudagrass on Forage Accumulation, Botanical Composition, and Nutritive Value
Authors: Marcia P. Quinby, Renata L. G. Nave, R. Mark Sulc, Miguel S. Castillo, Gary E. Bates, Liesel G. Schneider, and David W. McIntosh
In order to utilize alfalfa alone or in mixtures with grasses, defoliation management practices must be evaluated to assess their performance. The objective was to determine the forage accumulation and nutritive value of alfalfa grown as a monoculture and in mixtures with tall fescue or bermudagrass subjected to four harvest intervals (clipped every 21, 28, 35, and 42 days).

Link Pointer Using a Browntop Millet Companion Crop to Aid Native Grass Establishment
Authors: Jonathan D. Richwine, Patrick D. Keyser, Dennis W. Hancock, and Amanda J. Ashworth
The lack of forage production during the seedling year is a barrier to wide-scale adoption of native warm-season grasses (NWSG). To address this, two NWSG establishment experiments were conducted in Knoxville, TN, 2016–2018, to determine the efficacy of big bluestem and switchgrass establishment with browntop millet as a companion crop.

Link Pointer Identifying Barriers to Forage Innovation: Native Grasses and Producer Knowledge
Authors: Patrick D. Keyser, Susan Schexnayder, Adam Wilcox, Gary E. Bates, and Christopher N. Boyer
Adoption of native warm-season grasses (NWSGs) in the tall fescue belt is limited despite studies documenting the potential contribution of these forages to profitable beef production. On the basis of two surveys conducted in Tennessee, a survey of beef producers and a survey of agricultural professionals, we evaluated perceptions of NWSG forages and how those perceptions could influence their adoption.

Link Pointer Continuous Grazing of Mixed Native Warm-season Grass in the Fescue Belt
Authors: Kyle A. Brazil, Patrick D. Keyser, Gary E. Bates, Arnold M. Saxton, Elizabeth D. Holcomb
Continuous, season-long (May–August) grazing is the most commonly used grazing strategy among tall fescue belt beef producers. However, little information is available regarding the feasibility of managing native warm-season grass pastures in this region with continuous, season-long grazing. We compared stand sustain-ability, beef cattle performance, and pasture production between continuous, season-long grazing and heavy-early, a modified continuous grazing strategy, on mixed-pastures.

Link Pointer Seasonal Hay Feeding for Cattle Production in the Fescue Belt
Authors: Christopher N. Boyer, Dayton M. Lambert, Andrew P. Griffith, Christopher D. Clark, and Burton English
We determined how pasture and grazing management practices affected the number of days hay was fed to cattle by season. Data were collected from a survey of Tennessee cattle producers. Days of cattle on hay varied across seasons because of variations in forage production and weather. The number of days hay was fed to cattle varied with pasture-animal management practices such as rotating pastures, forage mixtures, and weed management strategies. Having mixtures of cool- and warm-season grasses reduced the number of days on hay in the winter, spring, and summer months indicating benefits from diversified forages.

Link Pointer Evaluation of Eastern Gamagrass and a Sorghum × Sudangrass for Summer Pasture
Authors: Patrick D. Keyser, Christopher M. Lituma, Gary E. Bates, Elizabeth D. Holcomb, John C. Waller, and Andrew P. Griffith
Improved summer forage production is important in forage systems dominated by cool-season perennial grasses. Improved forage may be especially important for heifer development. Therefore, we compared two summer forage options, a perennial, eastern gamagrass, and a widely used summer annual, sorghum × sudangrass hybrid, as options for providing summer pasture for bred heifers.

Link Pointer Overseeding Cool-Season Annual Grasses into Dormant Lowland Switchgrass Stands
Authors: Pattarawan Watcharaanantapong, Patrick D. Keyser, David W. McIntosh, and Andrew P. Griffith
Improved use of the land resource used to grow switchgrass, whether for biomass or forage production, could be achieved by dormant-season overseeding with cool-season annual grasses.

Link Pointer Forage Mass, Nutritive Value, and Economic Viability of Cowpea  Overseeded in Tall Fescue and Sorghum-Sudangrass Swards
Authors: Renata L. G. Nave, Marcia P. Quinby, Andrew P. Griffith, Michael D. Corbin, and Gary E. Bates
Cowpea (CW) is being considered as an alternative feed source in the southern U.S. Legume–grass mixtures are known to provide greater forage mass compared with unfertilized grass monocultures; however, research is needed to evaluate alternatives for increasing forage availability during the summer. The objective of this study was to quantify forage mass, nutritive value, and economic viability of CW overseeded in tall fescue (TF) and sorghum × sudangrass hybrid × Sorghum sudanese swards seeded at different rates.

Link Pointer Harvest Interval Effects on the Persistence and Productivity of Alfalfa Grown as a Monoculture or in Mixtures in the Southeastern United States
Authors: Marcia P. Quinby, Renata L. G. Nave, Gary E. Bates, and David W. McIntosh
For alfalfa to be profitable in the southeastern United States, enhanced persistence is required.

Link Pointer Winter Grazing Stockpiled Native Warm-Season Grasses in the Southeastern United States
Authors: Neal W. Tilhou, Renata L. G. Nave, J. Travis Mulliniks, and Zachary D. McFarlane
In the Southeastern United States, native warm-season grasses (NWSG) are not harvested during autumn to rebuild root reserves, resulting in de facto stockpiled winter forage. Senesced NWSG forage is considered nutritionally inadequate by temperate livestock managers, but comparable forage is regularly utilized in rangeland systems. This experiment compared the forage characteristics of two NWSG pastures: switchgrass and a two species mixture of big bluestem/indiangrass to tall fescue.

Link Pointer Seasonal and Diurnal Relationship of Forage Nutritive Value and Mass in a Tall Fescue Pasture Under Continuous Stocking
Authors: Renata L. G. Nave and Michael Dereck Corbin
Monitoring forage mass and nutritive value of pastures are encouraged to ensure adequate and efficient grazing management. For on‐farm monitoring, reliable instruments such as the rising plate meter (RPM) are useful and easy to achieve. The objective of this research was to verify the relationship between measurements of RPM (MRPM) to forage nutritive value based on seasonal and diurnal changes within a tall fescue sward under continuous stocking management.

Link Pointer Forage Warm-Season Legumes and Grasses Intercropped with Corn as an Alternative for Corn Silage Production
Authors: Renata L. G. Nave and Michael Dereck Corbin
The purpose of this study was to determine the yield and nutritive value potential of warm-season annual forages intercropped with corn for silage production. Intercropped forages can be harvested and ensiled with corn for silage production or can be left with the corn residue after harvesting to be grazed on in integrated crop-livestock systems.

Link Pointer Alternatives to Conventional Nitrogen Fertilization on Tall Fescue and Bermudagrass
Authors: Michael Dereck Corbin, Renata L. G. Nave, Gary E. Bates, D.M. Butler, and S. A. Hawkins
Alternatives to conventional N fertilization on tall fescue and bermudagrass were studied at the University of Tennessee. The objective of this study was to evaluate the effect of different sources of N, to include two perennial and one annual legume species, on HM and forage nutritive value of tall fescue and bermudagrass pastures.

Link Pointer Improving Nutritive Value of Native Warm-Season Grasses with the Plant Growth Regulator Trinexapac-Ethyl
Authors: Neal W. Tilhou and Renata L. G. Nave
Gibberellin inhibitors can alter plant regrowth and forage value. This study assessed the impact of trinexapac-ethyl [TE; ethyl 4-(cyclopropyl-hydroxymethylene)- 3,5-dioxo-cyclohexane-1-carboxylate] on fall NWSG forage. Application of TE occurred in late July at four levels (0, 0.3, 0.6, and 1.2 kg a.i. ha–1) to switchgrass and a mixed sward of big bluestem and indiangrass during 2016 and 2017.

Link Pointer Management of Native Warm-Season Grasses for Beef Cattle and Biomass Production in the Mid-South USA
Authors: W.M. Backus, John C. Waller, Gary E. Bates, C. A. Harper, Arnold Saxton, David W. McIntosh, J. Birckhead, and Patrick D. Keyser
Native grasses, such as switchgrass, big bluestem, indiangrass, and eastern gamagrass may be capable of providing desirable summer forage for cattle as well as a source of biomass for renewable energy.

Link Pointer Influence of Height-Based Management on Forage Nutritive Value of Four Warm-Season Forage Grasses
Authors: Christine H. Gelley, Renata L. G. Nave, and Gary E. Bates
Harvest timing is an influential factor in providing animals with high quality forage. Height-based management is commonly practiced to determine timing of cutting or grazing. This study aimed to observe nutritive value changes in tall- and short-growing warm-season grasses with repeated cuttings.

Link Pointer Utilization of Spent Microbial Biomass as an Alternative Crop Nitrogen Source
Authors: Casey T. Sullivan, Rebecca M. Harman, Neal S. Eash, James A. Zahn, John J. Goddard, Forbes R. Walker, Arnold M. Saxton, Dayton M. Lambert, David W. McIntosh, William E. Hart, Robert S. Freeland, and John E. Morrison, Jr.
Spent microbial biomass (SMB), a nutrient-rich co-product of industrial white biotechnology processes, is produced in substantial quantities alongside high-value products and most often disposed of in landfills or incinerated. Alternatively, SMB could be reused as a land-applied N source in agricultural crop production, reducing the environmental and economic footprint of synthetic fertilizers. This research compares SMB applied at different rates to current farmer practice fertilizer use in tall fescue and corn production.

Link Pointer Cultivar and Phosphorus Amendment Impacts on Organically Managed Forage Cowpea Yield and Composition
Authors: Samantha L. Hill, David A. Verbree, Gary E. Bates, and David M. Butler
Cowpea is a warm-season legume with many traits that make it an attractive forage or cover crop for organic systems. Eight cowpea cultivars were evaluated under organic management at two locations for stand establishment, forage yield and quality, and weed biomass.

Link Pointer Drivers of Grazing Livestock Efficiency: How Physiology, Metabolism, Experience and Adaptability Influence Productivity
Authors: J. Travis Mulliniks, Emily R. Cope, J.D. Hobbs, and Richard C. Waterman
To achieve this metabolic adaptability or flexibility, beef cows need to be suited to their environment and have the ability to acclimate to environmental changes. The purpose of this proceedings paper is to identify and describe factors that influence range cow efficiency and ultimately contributes to the sustainability (both from a productivity and economic view point) of range cows in extensive enterprises.

Link Pointer Forage Nutritive Value and Herbage Mass Relationship of Four Warm-Season Grasses
Authors: Christine H. Gelley, Renata L. G. Nave, and Gary E. BatesTo provide animals with high quality forage, practical methods are needed to estimate nutritive value to optimize harvest timing. The objective of this study was to develop such models to estimate warm-season forage nutritive value in the southeastern United States.

Link Pointer Utility of Aminocyclopyrachlor for Control of Horsenettle and Tall Ironweed in Cool-Season Grass Pastures
Authors: William P. Phillips, Trevor D. Isreal, Thomas C. Mueller, Gregory R. Armel, Dennis R. West, Jonathan D. Green, and G. Neil Rhodes, Jr.
Because horsenettle and tall ironweed are difficult to control in cool-season grass pastures, research was conducted in Tennessee and Kentucky in 2010 and 2011 to examine the efficacy of aminocyclopyrachlor on these weeds.

Link Pointer Influence of Aminocyclopyrachlor Plus Metsulfuron on Seed Head Development and Forage Quality in Tall Fescue
Authors: Trevor D. Isreal, G. Neil Rhodes, Jr., Thomas C. Mueller, Gary E. Bates, and John C. Waller
When applied alone or in combination with MAT28 or aminopyralid, metsulfuron reduced seed heads and improved forage quality in tall fescue, but also caused injury and reduced spring yield. Also, metsulfuron applied alone or in combination with MAT28 or aminopyralid reduced total ergot alkaloid concentration and therefore can potentially reduce the severity of fescue toxicosis.

Link Pointer Forage Harvest Timing Impact on Biomass Quality from Native Warm-Season Grass Mixtures
Authors: David W. McIntosh, Gary E. Bates, Patrick D. Keyser, Fred L. Allen, Craig A. Harper, John C. Waller, Jessie L. Birckhead, and William M. Backus
Biomass production systems using native warm-season grasses can allow for an early-season harvest (for forage) followed by a dormant harvest (for biomass). This study was conducted to investigate the impact of harvest timing and grass species on the chemical composition of harvested forage and biomass.

Link Pointer Biomass and Integrated Forage/Biomass Yields of Switchgrass as Affected by Intercropped Cool- and Warm-Season Legumes
Authors: K. Warwick, Fred L. Allen, Patrick D. Keyser, A. J. Ashworth, Gary E. Bates, D. D. Tyler, P. L Lambdin, and Craig A. Harper
Switchgrass has potential as a biofuel feedstock for ethanol production on marginal soils not suitable for row crop production. Further, it is hypothesized that legumes may be interseeded into switchgrass to increase available soil nitrogen (N) and enhance switchgrass yields. Therefore the primary objective was to identify compatible legume species for intercropping with lowland switchgrass and determine if biomass yields and forage quality can be improved.

Link Pointer The Cost of Feeding Bred Dairy Heifers on Native Warm-Season Grasses and Harvested Feedstuffs
Authors: J. K. Lowe II, Christopher N. Boyer, Andrew P. Griffith, John C. Waller, Gary E. Bates, Patrick D. Keyser, and E. Holcomb
The objectives of this research were to determine the cost of feeding bred dairy heifers grazing native warm-season grasses (NWSG), with and without legumes, and compare the cost of grazing with the cost of rearing heifers using 3 traditional rations. The 3 rations were corn silage with soybean meal, corn silage with dry distillers grain, and a wet distillers grain-based ration. Results of this study suggest that SG was the most cost-effective NWSG alternative to harvested feeds for bred dairy heifer rearing.

Link Pointer Nitrogen Rate and Initiation Date Effects on Stockpiled Tall Fescue During Fall Grazing in Tennessee
Authors: Renata L. G. Nave, Rondineli P. Barbero, Christopher N. Boyer, Michael D. Corbin, and Gary E. Bates
In Tennessee, N is one of the most common limiting nutrients for tall fescue production. Rising prices for N fertilizer have pressured cow-calf producers in Tennessee to reevaluate N management alternatives. The objectives of this study were to determine the effect of initiation date and N fertilization on stockpiled tall fescue yield, nutritive value, animal performance during fall grazing, and overall profitability of the production system.

Link Pointer Nitrogen Fertilization and Native C4 Grass Species Alter Abundance, Activity, and Diversity of Soil Diazotrophic Communities
Authors: Jialin Hu, Jonathan D. Richwine, Patrick D. Keyser, Lidong Li, Fei Yao, Sindhu Jagadamma, and Jennifer M. DeBruyn
Native C4 grasses have become the preferred species for native perennial pastures and bioenergy production due to their high productivity under low soil nitrogen (N) status. One reason for their low N requirement is that C4 grasses may benefit from soil diazotrophs and promote biological N fixation. Our objective was to evaluate the impact of N fertilization rates (0, 67, and 202 kg N ha􀀀1) and grass species and big bluestem on the abundance, activity, diversity, and community composition of soil diazotrophs over three agricultural seasons (grass green-up, initial harvest, and second harvest) in a field experiment in East Tennessee, United States.

Link Pointer Improving Efficiency of Production in Pasture- and Range-Based Beef and Dairy Systems
Authors: J. Travis Mulliniks, Augustus G. Rius, M. A. Edwards, S.R. Edwards, J.D. Hobbs, and Renata L. G. Nave
Continued viability of production systems using pasture- and range-based grazing systems requires more rapid adoption of innovative management practices and selection tools that increase profitability by optimizing grazing management and increasing reproductive performance.

Link Pointer Switchgrass Yield and Stand Dynamics from Legume Intercropping Based on Seeding Rate and Harvest Management
Authors: Amanda .J. Ashworth, Fred L. Allen, Patrick D. Keyser, D.D. Tyler, Arnold M. Saxton, and A. M. Taylor
Intercropping legumes may reduce inputs and enhance sustainability of forage and feedstock production, especially on marginal soils. This approach is largely untested for switchgrass production, yet producer acceptance should be high given the traditional use of legumes in forage/agricultural systems. Intercropping selected legumes in switchgrass may enhance forage quality and yield while reducing nonrenewable inputs, fertilizer costs, and emissions/runoff to air and groundwater.

Link Pointer Dormant-Season Planting and Seed-Dormancy Impacts on Switchgrass Establishment and Yield
Authors: Patrick D. Keyser, Amanda J. Ashworth, Fred L. Allen, and Gary E. Bates
Establishment failures linked to seed dormancy are a challenge to wide-scale use of switchgrass for biomass feedstock and forage production. One prospective strategy for breaking dormancy is dormantseason planting.

Link Pointer Breakeven Price of Biomass from Switchgrass, Big Bluestem, and Indiangrass in a Dual-Purpose Production System in Tennessee
Authors: Christopher N. Boyer, Andrew P. Griffith, David W. McIntosh, Gary E. Bates, Patrick D. Keyser, and Burton C. English
Producers considering a dual-purpose production system for native warm-season grasses will be confronted with several complex decisions about how to manage yield, quality, and cost of replacing nutrients while maximizing profits.

Link Pointer The Impact of Harvest Timing on Biomass Yield from Native Warm-Season Grass Mixtures
Authors: David W. McIntosh, Gary E. Bates, Patrick D. Keyser, Fred L. Allen, Craig A. Harper, John C. Waller, Jessie L. Birckhead, and William M. Backus
With increased harvest opportunities native warm-season grasses, grown in the mid-South United States under a dual-harvest system, can increase harvest options for producers by supplying acceptable forage yield for both early harvests and still provide biomass production.

Link Pointer Forage Performance and Soil Quality in Forage Systems under Organic Management in the Southeastern United States
Authors: Sarah E. Eichler Inwood, Gary E. Bates, and David M. Butler
Interest is increasing in organic forage production and sod-based rotations in the southeastern United States, but research-based information is limited. A replicated field study was established to evaluate productivity and soil quality changes in five organically managed forage systems.

Link Pointer Displacing Inorganic Nitrogen in Lignocellulosic Feedstock Production Systems
Authors: Amanda J. Ashworth, Patrick D. Keyser, Fred L. Allen, Donald D. Tyler, Adam M. Taylor, and Charles P. West
Legume intercrops (partridgepea) and biochar may supply analogous N to synthetic fertilizers, thereby displacing inorganic N without altering feedstock quality. However, for inorganic N alternatives to be competitive on a break-even cost basis, greater biomass yields need to be obtained under these management practices.