Historically, the recommendation
for providing calcium to
the peanut pegging zone was
to apply 1,000 pounds per
acre of gypsum or the equivalent (broadcast
or banded) at bloomtime. This was
to be applied only if you did not have at
least 500 pounds of calcium per acre and
a calcium-to-potassium (Ca:K) ratio of
at least three-to-one (3:1)in a soil sample
taken from the pegging zone soon after
the peanuts emerge.
Since calcium is critical to germination,
it has always been recommended
that any peanut being produced for seed
should receive 1,000 pounds per acre of
gypsum at early bloom regardless of pegging
zone Ca and K levels.
Another Possibility
Then about 15 years ago, research was
done at UGA using lime at planting to
provide calcium to the pegging zone of
peanut. Important points about this recommendation
include: 1) This method
is only supposed to be used when lime is
recommended according to soil sample
results. If lime is used when it is not called
for, it can raise the pH above recommended
levels and cause micronutrient
deficiencies such as with manganese. 2) If
you use lime, it must be applied at planting
and it should not be deep turned. The
calcium in lime is not as soluble as the calcium
in gypsum. Therefore, if lime is applied
at bloomtime, it will not have
enough time to “break down” and be absorbed
into the developing peanuts.
A New Method
Finally, over the last three years, a new
technique of using liquid calcium chloride
or calcium thiosulfate through the pivot
during peak pod fill has been tested at
UGA and has shown promise for providing
calcium to the pegging zone. If gypsum
becomes in short supply, this method
may be a valuable alternative for calcium
application. Calcium chloride has also
been tested in dryland situations by applying
it in a band behind the presswheel
at planting. This may also be a technique
to consider.
Calcium Q and A
The following are a number of common
questions concerning providing calcium
to the pegging zone with up-to-date
answers.
Q: Is there any difference between gypsum
materials available?
A: No, not as far as the ability to supply
calcium to the pegging zone. Last year,
USG 500, PCS Wetbulk, AgriCal
(smokestack) and even a new product
called “Gypsoil” were tested and seem to
perform equally. Selection
can be made
based on factors such
as product availability
and how well the
material handles and
is applied.
Q: Is it better to
use lime or gypsum
for dryland peanuts?
A: Gypsum! During
the last two years,
gypsum at bloomtime
has outperformed
lime at planting
as far as providing
calcium to the pegging
zone. This makes sense when you
think about it, since the calcium in lime
is less soluble than the calcium in gypsum
under limited water situations in dryland
production, the calcium in lime may not
become as available compared to when it
is under irrigation.
Q: Have the calcium recommendations
changed since the shift from small-seeded
to large-seeded runners?
A: Technically, no. Research data from
2008 to 2010 showed that both the 500
pounds per acre calcium in the pegging
zone requirement and the 1,000 pounds
per acre gypsum application rate overall,
appear to hold for large-seeded runners.
However, it is clear that following this
recommendation is more important for
large-seeded runners, and especially for
GA 06G. Also, when the pegging zone
calcium is between 500 and 750 pounds
per acre, you are in a “grey area” and again
this is where calcium chloride or calcium thisosulfate applied through center pivots
may be most beneficial.
Q: Are foliar calcium applications recommended
on peanuts?
A: No. This one is abundantly clear.
Foliar calcium products recommended in
the one quart per acre range that are
sprayed on the leaves in total spray volumes
of 10 to 20 gallons per acre do not
provide enough calcium. Even if it did, it
does not get translocated from the leaves
to the developing pods.
Q: Isn’t putting calcium chloride or
calcium thisoulfate liquids through a center
pivot a foliar application? I mean the
water hits the leaves, right?
A: No. Putting these “liquid calciums”
through a center pivot is a soil-applied
application. When putting out that much
water per acre, even though it hits the
leaves initially, it basically runs off and is
applied to the soil. Think of it this way,
when you foliar feed, you apply approximately
10 gallons per acre final spray
volume. When you apply one acre-inch,
you are applying approximately 27,000
gallons of water – a huge difference.
Q: So, do you recommend putting calcium
chloride or calcium thiosulfate
through center pivots? And does it replace
using gypsum?
A: Yes and No. Based on research data
from the last three years, calcium chloride
and calcium thiosulfate applied through
a center pivot (to supply approximately 25
pounds per acre of highly soluble calcium
during bloom) improved yield, calcium in
the seed and germination compared to
the untreated check. However, these products
do not increase the soil test calcium
levels after harvest near as high as gypsum.
So, in that regard, it does not replace gypsum.
Again, these two products applied
with center pivot irrigation appear to have
the best fit when the pegging zone calcium
levels are in that “grey area” of 500
to 750 pounds calcium per acre. If the
pegging zone calcium level is below 500
pounds per acre, then gypsum should be
applied instead.
Q: Can I apply gypsum at planting?
A: This is not recommended at this
point because there is always a chance
that with enough rain or irrigation water
early on, the calcium in gypsum could
leach below the pegging zone. This is especially
true on deep sandy soils.
Q: Should I split my gypsum applications
and put some on at planting and
some at early bloom?
A: This is also not recommended at
this time. However, research studies are
being conducted to see if there may be a
benefit to this timing of application.
Q: How late in the season is too late to
put out gypsum?
A: Gypsum should be applied at “early
bloom” or approximately 30 to 45 days after
planting depending on growing conditions.
Once you get past 100 days after
planting, the majority of pods have
probably already absorbed the proper
amount of calcium or not. After 100 days,
tractor damage by running over lapped
vines is not desirable. PG |
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