Arkansas - Agricultural Communication Services - University of ...

AAES Research Series 488
Results and Discussion
Plant height and tiller density increased with plant
maturity (P < 0.05). Plant height at harvest increased from
36.7 to 88.6 in between harvest dates 1 and 10, respectively.
Tiller counts for harvests 1 and 10 were 7.5 and 43.9
tillers/ft 2 , respectively (Table 1). The number of tillers and the
overall trend toward greatly increased tiller density that was
observed in this study was comparable with a report by
Coblentz et al. (1998), in which EGG was harvested at several
stages of growth over a calendar interval that was
comparable.
The percentage of leaf tissue varied over harvest dates;
the highest percentage was observed on the first harvest date
(83.2%) and the lowest on harvest date 8 (59.9%). Tiller
counts appeared to affect the percentage of stem tissue in
EGG. Tiller counts increased (P < 0.05) from 17.0 to 43.9
tillers/ft 2 between June 5 and July 17; concurrently, the percentage
of stem tissue declined (P < 0.05) from 23.8 to 15.9%
over this time period. Percentages of leaf observed in this
study were generally higher than those reported in other
warm season perennial grasses. Yields of DM increased (P <
0.05) with plant maturity from 1,111 lb/acre on harvest date 1
to 8,944 lb/acre on harvest date 10. Our yields of EGG are
within the ranges commonly reported in other studies.
The chemical composition of whole-plant EGG is
shown in Table 2. In this study, the concentration of NDF in
the whole plant was 66.2% on the first harvest date (May 15)
and increased (P < 0.01) to 79.4% by the eighth harvest date
(July 3). Evidently, the heads in the whole plant sample contributed
to lower fiber composition. The fiber composition of
leaf and whole plant is described by the following equations:
Whole plant NDF % = 66.0 + 0.4258 (days) – 0.0038
(days) 2
Leaf NDF % = 66.7 + 0.3685 (days) – 0.0030 (days) 2
Whole plant ADF % = 33.2 + 0.2859 (days) – 0.0020
(days) 2
Leaf plant ADF % = 31.8 + 0.3918 (days) – 0.0078 (days) 2
+ 0.0001 (days) 3 . The concentration of NDF and ADF were
consistent with findings reported by Coblentz et al. (1998); in
that study, EGG harvested at boot stage, anthesis, and full
maturity had NDF concentrations of 69.4, 73.1, 78.0%,
respectively. Respective concentrations of ADF were 35.3,
39.6, and 44.8% on these same harvest dates (Coblentz et
al., 1998).
The CP content of the whole-plant EGG decreased linearly
(P < 0.01) with maturity: whole plant CP % = 14.2 -
0.1290 (days). The CP concentration in the leaves was best
described (P < 0.01) by a quadratic equation: Leaf CP % =
16.3 - 0.2393 (days) + 0.0017 (days) 2 . Concentrations of CP
declined from 14.4 to 6.3% in the whole plant and from 16.9
to 7.9 % in leaf samples over the course of the study. The
declining concentrations of CP observed over time are consistent
with trends observed in numerous other reports
involving EGG and other perennial warm-season grasses.
Implications
Eastern gamagrass produces high yields of DM that
increases with plant maturity. However, nutritive quality
declined because the concentration of CP was higher at early
harvesting dates and declined with maturity and NDF and
ADF concentrations increased with maturity. The concentrations
of CP and fiber were not dramatically different in leaves
compared to whole-plant samples of EGG. Based on DM
yield and nutritional characteristics, the first harvest of EGG
should occur in late May or early June.
Literature Cited
Coblentz, W.K., et al. 1998. J. Dairy Sci. 81:150.
Coblentz, W.K., et al. 1999. Prof. Anim. Sci. 15:211.
Fine, G.L., et al. 1990. Registration of ‘Pete’ eastern
gamagrass. Crop Sci. 30: 741.
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