A2O-Lancastar Farming, Saturday, October 15, 1988
By Dr. John E. Baylor
Director of Market Development
Beachley-Hardy Seed Company
DR. JOHN E. BAYLOR
Director of Market
Development
Beachley-Hardy Seed Co.
After more than 40 years
studying and working as a practi
cal plant scientist, I still sometimes
think I should have been an Ag
Engineer. It would be much easier
it seems to me, to explain the stres
ses and strains of a piece of metal,
for example, than to explain the
effects of light, temperature, mois
ture, and all of the other factors on
growing forage plants. Engineers,
of course, may strongly disagree
on this point.
Nevertheless, I’ve chosen the
plant sciences, and light, tempera
ture, moisture, and other factors do
impact on plant growth and qual
ity. In today’s column, let’s take a
brief look at the results of a study
or two that point out some of these
affects.
Quality - The Key
First, let’s agree that profitable
ruminant livestock production
depends on feeding quality forage.
But, experts agree, the forages
you feed can be no more nutritious
than the crop you harvest. That’s
why it all starts back in the field
with timely cutting, and, whether
the crop is legume, grass, or a com
bination, quality is most closely
related to the maturity of the plants
at time of harvest Young, imma
ture plants are high in protein and
low in fiber or lignin, but as hay
matures, fiber content increases
and feeding value goes down.
The above statements are cer
tainly true. But, even when all of
the harvest rules are followed, we
still frequently note measurable
differences in quality. Why?
Hay Crop Silage
Hay crop silage is often the for
age feed where quality questions
arise. While silage is an efficient
method of conserving the feed val
ue of a hay crop, hay crop silage is
also one of the most inconsistent
and variable foodstuffs used in
cattle rations.
Kansas State University forage
specialist Keith Bolsen suggests
nine distinct but interdependent
factors affecting silage quality. Of
these, he says, moisture level is the
most critical single factor. Mois
ture level is not a simple factor
because as alfalfa matures, the
moisture content that is best for
good silage compaction changes -
and compaction is the key to oxy
gen exclusion, probably the next
most critical factor. Recom
mended maturity at which alfalfa
should be cut for silage ranges
from late bud to early bloom for
first cut alfalfa, and up to 'A bloom
for other cuttings. And, recent stu
dies show that maturity affects
other variables critical to the ensil
ing qualities of the alfalfa crop.
detergent fiber, and non-structural
carbohydrates in the alfalfa plant.
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These changes have been studied
from time to time over the years
and most recently reported by
workers in Idaho. In brief, here’s
what they found:
1. There was a strong tendency
for the percentage of crude protein
in the plant to fall during daylight
hours and rise again at night.
2. Carbohydrates (energy)
showed a reverse pattern as levels
rose during the day and declined at
night.
This, workers agree, is a normal
light/dark response characteristic
of green plants and has long been
known to occur in alfalfa. But,
what the Idaho scientists also
found was that there is an apparent
maturity threshhold that has a
major affect on the level of car
bohydrates reached and retained in
the alfalfa herbage at night. These
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Building A Name Toda
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carbohydrates are the source of
energy for the plants life functions,
and they’re probably the main
source of energy for fermentation
during ensiling.
In the Idaho study, the same pat
tern occurred for all cuttings:
example, as plants got older, car
bohydrate levels in the plants
increases. They noted, too, that
cutting schedules the previous year
also had an influence on carbohy
drate levels of the first crop. For
instance, levels were lower follow
ing a four-cut system as compared
to a three-cut system. Both of these
observations, they say, suggest
that the level of underground stor
age carbohydrates was a key factor
affecting the carbohydrate level in
forage.
It appears highly likely that
alfalfa cut for silage should have a
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maturity at which 6-7 percent
water soluble carbohydrates are
present. These levels could prob
ably be attained in the morning for
first cutting at early bloom follow
ing a three-cut schedule the previ
ous year, but when alfalfa was cut
four times the previous year, a late
afternoon harvest would be better.
Sounds complicated doesn’t it?
Maybe I should have chosen
another science as a profession.
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