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Influence of Moisture Concentration at Baling on Storage Characteristics
of Bermudagrass Hay
J. E. Turner, W. K. Coblentz, D. A. Scarbrough, D. W. Kellogg, K. P. Coffey, L. J. McBeth, and R.T. Rhein 1
Story in Brief
Concentrations of moisture > 20% are known to cause spontaneous heating and associated deleterious effects
on forage nutritive value in hay. Alfalfa (Medicago sativa L.) has been thoroughly studied in this respect, but relatively
little is known about these relationships in warm season grasses. ‘Greenfield’ bermudagrass [Cynodon dactylon (L.)
Pers.] was packaged in conventional rectangular bales at 21.9, 26.5, and 30.2% moisture (LM, MM, and HM, respectively).
The MM and HM bales accumulated more (P < 0.05) heating degree days >95°F and exhibited greater (P < 0.05)
mold development than the LM bales. Dry matter recovery was greater (P < 0.05) for LM and MM bales than for HM
bales.
Introduction
In the southern USA the harvest of bermudagrass
often coincides with periods of high relative humidity and a
relatively high probability of regular rainfall events. High relative
humidity can extend the period needed to dry hay in the
field (Moser, 1995), thereby increasing the probability of a
rainfall event on the hay prior to packaging. These factors
often necessitate baling at higher than optimal moistures or
delaying harvest until more favorable weather conditions
occur.
Concentrations of moisture >20% in alfalfa and
bermudagrass hays produce spontaneous heating, mold
growth, and deleterious changes in forage nutritive value
(Collins et al., 1987; Coblentz et al., 2000). Previous
research (Coblentz et al., 2000) has indicated that bermudagrass
hay exhibits two distinct temperature maxima; these
occur immediately after baling and then between 5 and 20 d
of storage. It is especially important to develop a clear understanding
of storage characteristics over a 65-d storage period
for bermudagrass, which is the most important forage grown
throughout the southeastern USA (Burton and Hanna, 1995).
The objectives of this research were to characterize the
effects of moisture concentration at baling on storage characteristics
of bermudagrass hay.
Experimental Procedures
An approximately 15-yr-old stand of “Greenfield”
bermudagrass grown at the University of Arkansas Forage
Research Area located in Fayetteville was selected for this
trial. The experimental forage was the second cutting for
1999. On 13 July 1999, the bermudagrass forage was mowed
in three blocks of 12 swaths each. Swaths in each block were
randomly assigned to one of the three moisture concentrations
(30.2, 26.5, and 21.9%; HM, MM, and LM, respectively),
which were chosen to produce intense, moderate, and
minimal heating and similar associated changes in forage
nutritive value. For each moisture treatment, 12 conventional
bales (average size = 1.57 ft by 1.25 ft by 3.14 ft) were made
from each block. Six bales from each group of 12 were placed
side by side (strings up) on top of the wooden pallets. The
remaining six bales from each treatment were positioned in
the same orientation on top of the first six bales, thereby creating
stacks two bales high and six bales wide for each field
replication of each treatment. Individual stacks containing 12
bales were surrounded on the sides and top by dry bales of
wheat straw to limit the effects of diurnal variations in ambient
temperature.
All bales were weighed and measured for length prior
to being placed on the pallets. The length and weight of the
bales were used to determine the density of each hay package.
Height and width of bales were not measured; prior observations
indicated these measurements to be uniform with our
baler. Two bales from each block were visually appraised for
mold growth on d 65 of storage by the method of Roberts et
al. (1987). Prior to being placed in the stack for storage, four
bales from each block had single thermocouple wires inserted
into the center of each bale. Bale temperatures were
recorded twice daily (0630 and 1500 h) during the initial 14
d of storage and once daily (1500 h) during the remainder of
the storage period. The observed temperature was considered
to be the mean internal bale temperature for a given day,
except during the initial 14 d when the mean of the two observations
was used. Heating degree-days >95°F (HDD) were
calculated by subtracting 95°F from the recorded daily mean
internal bale temperature and summing these differences over
1 All authors are associated with the Department of Animal Science, Fayetteville.
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