Arkansas - Agricultural Communication Services - University of ...

Arkansas Animal Science Department Report 2001
ground cover. Forage samples were dried to a constant weight
in a forced-air oven (55°C) and yields were expressed on a lb
DM/acre basis.
Data for each location were analyzed independently as
a split-plot design using the GLM procedure of SAS (SAS
Inst., Inc., Cary, NC). Whole plots were arranged in a 2 x 4
factorial design that included two initiation dates (August 8
or 10, September 6) and four fertilization rates (0, 33, 66, or
99 lb N/acre). The subplot treatment factor was fall harvest
date (October 18 or 19, November 8 or 9, November 29 or 30,
and January 8 or 9). Whole-plot sums of squares were partitioned
to test for main effects of stockpiling initiation date
and N fertilization rate, and to test for their associated interaction;
the mean square for the stockpiling initiation date x N
fertilization rate x block interaction was used as the error
term. Fall harvest dates and all interaction terms with fall harvest
date were tested for significance with the residual error
mean square.
Results and Discussion
Mean daily air temperatures and monthly precipitation
patterns are shown in Figures 1 and 2, respectively. Ambient
air temperatures appeared to follow similar trends at both
locations. Temperatures remained relatively high throughout
the mid- and late-summer months and were coupled with
very little rainfall (Figure 2), which resulted in droughty conditions
during this time period. Total precipitation was higher
at Fayetteville between August and November, which was
the period when stockpiling occurred.
At Fayetteville, the stockpiling initiation date x fall
harvest date interaction was significant (P = 0.0002); therefore,
only interaction means are presented in Table 1. Dry
matter yields of stockpiled bermudagrass initiated on August
8 decreased (P < 0.05) between November 8 and November
29, but did not change (P > 0.05) between October 18 and
November 18 or between November 29 and January 8. Yields
for forage that began the stockpiling period later (September
6) were greatest (P < 0.05) on the November 8 sampling date.
At Batesville, the stockpiling initiation date x fall harvest date
interaction was significant (P < 0.0001), while the main effect
of N fertilization rate approached significance (P = 0.057).
Therefore, main effect means of N fertilization are presented
in addition to interaction means in Table 2. Previously, Hart
et al. (1969) observed similar increasing trends for yields of
stockpiled 'Coastal' bermudagrass in response to increased
rates of N fertilization. Dry matter yields of stockpiled
bermudagrass initiated on August 10 and September 6 followed
trends similar to those observed for bermudagrass at
Fayetteville.
Stockpiled bermudagrass yields on the initial sampling
date in our study were lower than those reported for stockpiled
bermudagrass harvested from early- to mid-November
in Georgia (Hart et al., 1969). In addition, yields throughout
the sampling period were lower than those reported by
Coblentz et al. (1998) for stockpiled 'Greenfield' bermudagrass
harvested during late fall and early winter in Arkansas.
Unusually high temperatures and infrequent rainfall events
during the early fall clearly influenced trends for yields of
stockpiled bermudagrass throughout our study. Unusual
weather patterns during the sampling period may have also
contributed to unexpected trends for stockpiled bermudagrass
yields. The approximate onset of fall dormancy for bermudagrass
in Arkansas generally occurs in mid-October, after
which little accumulation of bermudagrass forage is expected
to occur. However, the first killing freeze at both experimental
locations in our study occurred on approximately October
9; low temperatures on this date were 27 and 30°F at
Fayetteville and Batesville, respectively. Therefore, high temperatures
and low moisture availability during the early fall,
coupled with an early killing frost probably limited the yield
potential of stockpiled bermudagrass on the first sampling
date. Dry matter yields were generally the highest at both
locations on the early-November sampling date (Tables 1 and
2). This phenomenon was a result of increased temperatures
and rain-fall events during the first sampling interval, which
promoted renewed bermudagrass growth between mid-
October and early-November.
Implications
Yields of stockpiled bermudagrass at Fayetteville and
Batesville, AR remained relatively low throughout the late
fall and early winter, never producing more than 1,565 lb of
forage DM/acre. However, unusual weather events that
occurred throughout late fall and early winter contributed to
unexpected trends for stockpiled bermudagrass yields.
Literature Cited
Burton, G. W., et al. 1963. Agron. J. 55:500-502.
Coblentz, W. K., et al. 1998. Ark. Anim. Sci. Research Series
464. p. 43-47.
Doss, B. D., et al. 1966. Agron. J. 58:510-512.
D’Souza, G. E., et al. 1990. Am. J. Alternative Agric. 5:
120-125.
Hart, R. H., et al. 1969. Agron. J. 61:940-941.
Hill, G. M., et al. 1993. J. Anim. Sci. 71:3219-3225.
Hitz, A. C., and J. R. Russell. 1998. J. Anim. Sci. 76:404-415.
Jolliff, G. D., et al. 1979. Agron. J. 71:91-94.
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