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Yield and Nutritive Value of Eastern Gamagrass at Ten Harvest Dates
M. S. H. Mashingo, D. W. Kellogg, W. K. Coblentz, D. A. Scarbrough,
K. S. Anschutz, J. E. Turner, and R. Panivivat 1
Story in Brief
Yield of ‘Pete’ eastern gamagrass (EGG; Tripsacum dactyloides L.) was evaluated at University of Arkansas
Forage Research Farm in Fayetteville, AR. Forage samples were harvested at 7-day intervals beginning on May 15 and
ending on July 17, 2000. As EGG matured, plants grew (P < 0.05) from 36.7 to 88.6 inches in height, tiller density
increased from 7.4 to 43.9/ft 2 , and DM yield improved from 1,111 to 8,944 lb/acre. Leaf tissue comprised between 59.9
and 83.2% of the forage DM over the sampling period with the remainder being stems and heads. Neutral detergent fiber
(NDF) increased with plant maturity and ranged from 66.2 to 79.0% in whole-plant samples and from 67.1 to 78.5% in
leaf samples. Acid detergent fiber (ADF) ranged from 32.3 to 44.5% in the whole plant and from 32.0 to 43.7% in leaves
during the experiment. Concentrations of CP declined from 14.4 to 6.3% in the whole plant and from 16.9 to 7.9% in
leaves as plants matured. With limited fertilization (50 lb N/acre), EGG demonstrated a tall growth habit, excellent DM
yields, and a high proportion of leaf within the canopy.
Introduction
Gamagrass is a perennial, warm season bunchgrass that
is native to the eastern half of the United States. It is adapted
to moist areas, and grows in clumps that may be more than 3
ft in diameter; plants may also attain heights of 5 to 10 ft.
Compared to other tall-growing, perennial warm-season
grasses that are native to the Midwest, growth and quality
characteristics of ‘Pete’ eastern gamagrass (EGG) have been
incompletely evaluated.
Interest in EGG gained momentum during the late
1980’s and 1990’s when the cultivar ‘Pete’ was developed
from native EGG populations in Kansas and Oklahoma (Fine
et al., 1990). Popularity of EGG has increased because of its
ability to produce large quantities of quality forage during the
summer months. Studies of the chemical composition of
EGG have indicated that concentrations of NDF are generally
high (> 60.0%), even at immature stages of growth
(Coblentz et al., 1999). The N content may exceed 2.0% at
the boot and anthesis stages of growth. Concentrations of
fibrous components in EGG resemble those reported commonly
for other warm-season grass species; therefore, the
proportion of cell wall in whole-plant tissue is high.
Concentrations of acid detergent fiber (ADF) have ranged
between 29.2 to 44.8% over several studies. The concentration
of ADF increases in leaf, stem, and whole-plant tissues
and has a positive relationship with plant maturity. EGG produces
good regrowth following defoliation, and this allows
multiple harvests during the growing season so the grass can
be grazed or conserved as hay or silage (Coblentz et
al., 1999).
Experimental Procedures
A pasture plot of EGG was established in rows spaced
40-in apart during Spring, 1999. The experimental site was
fertilized on May 1, 2000 with ammonium nitrate at a rate of
50 lb N/acre. The plot was divided into four blocks (162.5 x
162.5 ft); forage sampling was initiated on May 15, 2000.
Forages were harvested by hand-clipping 39 in of row at an
8-in stubble height with hand shears. On each harvest date,
the height of EGG was established by measuring the tallest
plants within each 39-in section of row that was sampled on
that date. Harvest dates were May 15, May 22, May 29, June
5, June 12, June 19, June 26, July 3, July 10, and July 17
(harvest dates 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, respectively).
Harvested samples were dried to a constant dry weight under
forced air at 122°F. Percentages of leaf and stem were determined
by separating individual leaves from stems at the leaf
collar. Reproductive heads were separated from the stem and
not included as stem tissue. Tiller counts were expressed as
the number of tillers/ft 2 .
Dried whole-plant and leaf samples were ground
through a 1-mm screen in a Wiley mill (Arthur H. Thomas,
Philadelphia). Both neutral detergent fiber (NDF) and ADF
were determined using batch procedures outlined by
ANKOM Technology Corp. (Fairport, NY). Concentration of
CP was calculated from the % N in each sample, as determined
by a modified Kjeldahl procedure (Kjeltech Auto 1030
Analyzer, Tecator, Inc., Herndon, VA).
1 All authors are associated with the Department of Animal Science, Fayetteville.
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