A26-Lancaster Farming, Saturday, May 27,1989
What This Rain , Rain, Rain Means To Your Crops
Rain Damaged
Ryelage-To Harvest
Or Not To Harvest?
There have been reports of rye
that was cut ten days ago but not
harvested because of the rain. Is it
now worth harvesting this mater
ial? This is not easy to answer
depending on the state of damage
to the rye. However, if a particular
farm is in dire need of forage, it
may be worth the risk of ensiling.
The big question is whether rain
damaged rye will ferment proper
ly or not
There are three requirements
for good fermentation during the
ensiling process; -1) an oxygen
free environment, 2) adequate
numbers of lactic acid producing
bacteria, and 3) adequate amounts
of soluble sugars for the bacteria
to grow. With the amount of mois
ture we’ve had, there should be an
adequate population of natural
occurring Lactobacillus organ
isms. The most limiting factor
would be the source of soluble
sugars. With the amounts of rain
fall we’ve had, much of the solu
ble nutrients in the rye is most
likely leached out.
If rain damaged rye is stored in
the silo, it may be worth adding
some ground com in to assure a
readable source of soluble sugar.
For wilted rye, I would suggest
adding about 2% ground com by
net weight. In other words, for
each ton of 60% moisture content
rye, add 50 lbs. of ground com.
S.C. Bosworth
Nitrogen Loss From
Heavy Rains
Two years in a row we have had
heavy rains in May resulting in
high potential nitrogen fertilizer
losses. This is a classic example of
why sidedressing is recom
mended. For farmers who were
planning on sidedressing, their
nitrogen is still in the bag or in the
bin or in the tank. For those who
put their nitrogen on preplant it is
hard to say where their nitrogen is
now. The big question is not
whether some of the nitrogen has
been lost but how much! For far
mers who are planning on side
dressing their nitrogen no adjust
ments need to be made at this
time. However, if planting con
tinues to be delayed by the wet
weather yield potentials may be
reduced and thus nitrogen fertiliz
er rates may need to be adjusted
accordingly. This is another
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advantage to sidedressing nitro
gen, it allows the farmer to wait
longer and gather more informa
tion before making a final nitro
gen fertilizer decision.
Farmers who have already
applied their nitrogen have fewer
options. It is difficult to predict
how much of the nitrogen has
been lost. We would expect losses
to be greatest on soils at the
extremes of drainage, i.e., in the
excessively well drained soils and
on the very poorly drained soils.
Plant color can be used as a crude
indicator of lack of nitrogen. Yel
low plants, where the yellow is
greatest on the lower leaves, usu
ally indicates nitrogen deficiency.
If the com is yellow at the 10 to 20
inch tall stage some additional
sidedress nitrogen (30-60 lbs./A)
should probably be applied.
This year for the first time it
will be possible to test the soil for
nitrate nitrogen just before side
dressing to determine if there is
enough nitrogen to grow the crop
or if additioifal nitrogen fertilizer
is needed. This test will provide
additional information to help the
farmer who is planning to sided
ress make a sound nitrogen man
agement decision and it may pro
vide some help to the farmer who
has already applied his nitrogen
but has lost some of it. Since, the
test is primarily designed for use
where little nitrogen has been
applied prior to sidedressing, its
use where large amounts of nitro
gen have been applied preplant
has not been thoroughly eval
uated. This test will be available
as a quick test on a limited trial
basis through the extension office
this year. However, nitrate nitro
gen analysis is available routinely
through Merkle Soil Testing Lab
at Penn State and through most
commercial labs. There are very
specific sampling and sample
handling requirements for this
test The details of this test and the
interpretation of the results and
recommendations are covered in
Agronomy Facts #l7 Nitrogen
Soil Test for Com in Pennsyl
vania, or by calling the office at
248-9618. The testing will be free.
You pull the sample. I’ll do the
test and give you results within 10
minutes if you wait. Sampling
procedures are critical. Call the
office for details.
Early Replant
Decisions With Corn
The past three weeks of rain and
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(717) 656-0783
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cool weather may result in poor
com stands in fields planted in late
April. It is still early enough in the
season that fields requiring
replanting can be planted to com
and maintain a relatively high
yield potential.
Making a decision whether to
replant is always difficult. The
major issue is, would the farmer
be better off with the reduced
stand from the original planting,
or would he be better off replant
ing and accepting the yield penal
ty associated with the later plant
ing date? Information from the
following table should help in
these decisions. The data is from
lowa State University, but the
response of com to planting dates
and populations should be fairly
similar. Information in the table is
based on relatively uniform
stands. In the real world, lower
stands are often somewhat uneven
and decisions need to be made as
to how much to subtract due to
unevenness of stand. An Illinois
study indicated yields are reduced
about 2% if the stand includes sev
eral small gaps of 1.5-3 feet.
Numerous 4-6 ft gaps reduced
yields by about 5-6%. Thus in
some cases, you may have to
reduce the percentages given in
the table according to your best
judgement. An added complica
tion can be the variation in height
of plants due to uneven
emergence. Recent studies indi
cate a “mixture” of plant heights
can result in significant yield
reductions - especially if plant to
plant emergence varies by 2-3
weeks.
To use the table, first consider
the “percent of maximum yields
for the May 10 planting date for
your reduced stand. For example,
if you ended up with a final stand
of 14,000, it means that the yield
potential is approximately 82 % of
what a full stand would produce.
If you replant to a full stand
(22,000-26,000) on the 20th of
May, yields in the range of
91-92% would be possible. In this
example, the extra yield (about
10%) may cover the cost of
replanting.
Replant decisions are rarely
easy. Before making decisions.
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accurately determine populations
and uniformity of stand. Certain
hybrids may have the ability to
form multiple ears at low popula
tions and partially compensate for
stand loss. Finally, determine the
- cost of replanting (tillable, seed,
additional chemicals, labor, etc.)
and estimate the likelihood of the
increased yield potential covering
these costs.
Influence of Planting
Date and Plant
Populations on
Yield Potential.
Population
(plants/A) 5-10
26,000
22,000
18,000
14.000
10.000
100
98
93
82
67
G. Benton, lowa Slate University.
R.G. Hartzler
& G.W. Roth
Wet Weather vs.
Good Weed Control.
What will happen to the pre
emergence herbicides that were
applied prior to the' heavy rains
over the past two weeks?
Rainfall is needed following
application of pre-emergence her
bicides to move the material to the
depth at which weed seeds germi
nate. With most materials, a half
inch of rain is adequate. The more
rain that occurs, the deeper the
herbicide will be moved into the
soil profile. Since the majority of
weeds germinate within the upper
0.5 inch of soil, if much of the her
bicide is moved significantly
below this depth, poor weed con
trol might occur.
Several factors influence the
rate of herbicide movement in the
soil profile, including chemical
properties of the herbicide, soil
properties, and quantity of rain
fall. Herbicides vary widely in
their potential for movement; a
relative mobility ranking of com
herbicides would be; Lasso=Dual
= Bladex > atrazine > Princep >
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Prowl. Lasso and Dual are more
susceptible to failure during wet
years than some other products
because they are absorbed primar
ily through the shoots of grasses.
If Lasso or Dual are leached below
the weed seeds where they only
contact roots of seedlings, they
will not provide adequate control.
The triazine herbicides are
absorbed by plant roots, and Prowl
is active on roots, so these herbi
cides can still be effective if leach
ed below the depth of shoot
emergence.
How deep will the herbicide be
leached? We are concerned about
Planting Date
5-20 6-1
Percent
92 '
91
85
76
62
the detection of herbicides in the
groundwater. These heavy rains
will increase the potential for
movement deep into the soil pro
file. However, when I say that her
bicide activity may be diminished
due to leaching, I am referring to
the herbicide being moved 3 - 4
inches into the profile. Although
this is still very shallow, it is deep
enough to reduce the herbicide’s
activity.
Another factor that may reduce
control is a decrease in herbicide
persistence. The length of persis
tence of a chemical may be
reduced under very wet condi
tions* resulting in a shorter period
of weed control. The combination
of greater leaching'and "shorter
persistence may result in late sea
son weed escapes in those fields
that had herbicides applied in late
April prior to the rain. Fortunate
ly, those weeds that emerge 4-6
weeks after crop emergence are at
a competitive disadvantage with
the crop. In most competition stu
dies, late emerging weeds' have
not caused significant yield losses.
A second problem that might be
associated with the recent wet,
cool weather is an increased
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6-10
84 71
83 70
78 66
69 58
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(Turn to Pag* A 27)
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