In this Issue:
Fall is the
best time to till a soil because the soil is usually dryer.
This means less possible compaction from the traffic of the
tillage process and better disturbance of compacted layers.
primarily use two types of tillage in the fall: 1) surface
tillage to prepare for the spring planting of corn and
soybeans; and 2) subsoiling, which is mainly done on
no-tilled/mostly no-tilled fields. Land is surface tilled,
also, for planting wheat and other fall seeded crops, but we
will concentrate on corn and soybeans here.
surface tillage is used on all soil types, it is mainly
beneficial on the more level and poorly drained soil types.
These soil types have poor surface and internal drainage which
cause delayed planting or poor stands and growth if high
amounts of residue are on the surface during cool wet springs.
Fall tillage reduces the amount of surface residue and allows
the soil surface to warm and dry faster in the spring. This
allows an earlier planting and sometimes a better corn stand,
which is helpful on these soils. Tillage also reduces internal
drainage and increases water loss by evaporation. These
characteristics of tillage are usually not that detrimental to
poorly drained fields because water is usually available to
the plant throughout the growing season. The reduced internal
water movement and increased water loss are detrimental to
soils that are not poorly drained. The increased water loss
will reduce yields if a droughty period occurs during the
growing season on soils that are well or moderately drained.
Therefore, tillage would usually not be recommended on these
is used on erodable land, remember to leave at least 30% of
surface covered with residue. This residue cover will greatly
help reduce erosion and help preserve some of the moisture
during the growing season.
tillage is mainly used on no-till land or mostly no-tilled
land. Farmers use it to increase internal drainage and loosen
the soil. This type of tillage is, by far, best done in the
fall because of the depth of tillage. The soil moistens from
the top down in the fall and dries from the top down in the
spring. Therefore, the subsoil will usually be dry enough to
shatter in the fall, but may remain too wet in the spring to
get proper shattering.
compaction exists, subsoiling can increase the yields by 10%
to 25% depending on severity of compaction. If compaction does
not exist, I have never measured a significant increase in
yields due to subsoiling. However, Agriculture Extension
Agents and farmers have measured economical yield increases
under these conditions. Therefore, there is a chance of a
yield increase by subsoiling uncompacted soil. However, the
chances are not great and an economic return for the
subsoiling would be questionable not to mention the extra
labor and management that would be required.
research indicates that over time continuous no-till systems
actually correct compaction that exists in a field. However,
subsoiling field end-rows and other high traffic areas to aid
in correcting compaction would be prudent.
Fall is an
excellent time for tillage, whether it be surface or subsoil
tillage. However, places and conditions where tillage has
proven to be beneficial are not great. The benefits of tillage
occur mainly on poorly drained soil for surface tillage and
compacted soils for subsoil tillage.
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Kentucky’s soybean producers believe that yields are no longer
increasing. Is this true? Are we approaching a yield barrier?
Many farmers expect good yields this year, but the Kentucky
Agricultural Statistics Service’s September estimate of the
average state yield is only 38 bushels per acre. Kentucky
first reached this yield level in 1992. Our all-time record
yield, 40 bushels per acre, occurred in 2001. The same yield
in 1992 and 2003 might suggest a plateau, but the record yield
occurred just two years ago, suggesting that yields may be
we know if yields are increasing or stagnant? Soybean yields
are determined by the yield potential of the variety,
management practices, soil type and the weather – primarily
rainfall. The amount of rainfall and when it occurs are
critical in Kentucky, causing much of the year-to-year
variation in yield (Fig. 1). This variation makes it difficult
or impossible to spot a yield plateau until it is well
established. Is the nearly constant yield from 1992 to this
year a plateau or just a run of years with bad weather? What
about the 1980’s? Its hard to say for sure, but one or two
years with excellent weather and record yields will destroy
any plateau and restore the upward trend, just as it did in
the early 1990’s.
Over the long haul, soybean
yields in Kentucky have
increased. Trend analysis of average state yields (data from
Kentucky Agriculture Statistics Service) in Kentucky from 1972
to 2002 suggests that yields increased at an average rate of
0.3 bushels per acre per year (Fig. 1).
That increase is less than 1% of the projected yield for 2003.
No wonder it is easy to get the impression that yields are not
increasing. The average rate of increase was a little higher
in Illinois (0.4 bushels per acre per year) where average
yields are usually higher than in Kentucky. We also evaluated
yield increases in selected high-yielding counties in Kentucky
and Illinois. The average increase was up to 0.4 bushels per
acre per year in Henderson and Davies counties in Kentucky and
0.5 and 0.8 bushels per acre per year in the Illinois
counties. By comparison, the increase in low yielding counties
in Kentucky and Illinois was much lower (only 0.1 to 0.2
bushels per acre per year). We always found that the yield
trend was upward but, at best, it was not very large and in
areas with low yield potential it was almost zero. Such small
increases are easily masked by variation in weather creating
the impression that yields have reached a plateau at times.
Looking at yields over 31 years (Fig. 1) makes the trend for
higher yields clear, but it doesn’t tell us if the stable
yields over the past 10 years represent the beginning of a
yield plateau or just a run of years with bad weather.
Plateau or not, yields now
are higher than they were 30 years ago, primarily because
modern varieties have higher yield potential, better agronomic
characteristics, and broader disease resistance. Are varieties
still improving? The average rate of increase in yield of the
three highest yielding varieties in each maturity group from
the Kentucky Soybean Performance tests was 0.3 bushels per
acre per year from 1975 to 2002, which is just about the same
as the increase in average state yields. Soybean varieties
available to Kentucky producers are constantly improving and
there is no indication that this trend will end soon, as the
highest yields over the 28 years (> 50 bushels per acre)
occurred in 2001.
Kentucky and Illinois demonstrate that soybean yields have
increased and I think they have the potential to keep
increasing slowly. The modest yield potential in Kentucky will
limit us to a slow increase, just like in the past, and the
year-to-year variability in yield may often mask the increase.
Is there anything that can be done to increase yields faster?
Research over the past 40 years at the University of Kentucky
and in other states has done a good job of defining the Best
Management Practices for growing soybean. This system starts
with good seed of the best high-yielding variety available.
Plant the seed in May or early June at an optimum population
in narrow rows on a soil with adequate levels of fertility. If
weeds and the soybean cyst nematode are controlled and harvest
losses minimized, you should have the potential for high
yields. Actual yield will depend on the inherent productivity
of the soil and the weather - neither of which can be
controlled. Unfortunately there are no magic bullets or
potions out there that will produce dramatic increases in
yield, but applying the Best Management Practices package and
praying for rain should keep Kentucky soybean yields edging
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Much of the
blame of the current soybean yield plateau has been directed
at Roundup Ready soybeans. One area of blame was with sudden
death syndrome. But, is this blame worthy?
Roundup Ready soybeans were first used on a wide scale in
1997, a severe epidemic of sudden death syndrome (SDS)
occurred in the southern Midwest. Of course, the southern
Midwest also experienced unusually wet weather that year.
Still, some accused the Roundup Ready soybean system for the
recently published article from Agronomy Journal (2003,
volume 95, pages 1140-1145), researchers evaluated the effects
of glyphosate herbicide on SDS and Fusarium solani f.
sp. glycines, the casual agent of SDS. The researchers
investigated ten Roundup Ready soybean varieties in central
and southern Illinois. They applied glyphosate herbicides when
the soybeans were at the V3 growth stage. They monitored SDS
development and compared their results to soybeans that were
not sprayed with glyphosate. The scientists found that
applications of glyphosate did not increase Fusarium
colonization of soybean roots. In addition, applications of
glyphosate did not increase SDS. The researchers did observe
different levels of variety tolerance to SDS.
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Roundup Ready soybeans more susceptible to SDS? The answer is
yes and no. Yes, some varieties were more susceptible to SDS
and no, some varieties were more tolerant to SDS. Don Hershman,
Extension Plant Pathologist, suggests that some earlier
Roundup Ready varieties were more susceptible to SDS because
of the agronomic package of the parent material. Most
companies rate soybean variety tolerance to SDS and other
pathogens. Those ratings are included in the Soybean Variety
home message is to check the variety disease tolerance ratings
before selecting your varieties, and to apply glyphosate to
Roundup Ready soybeans without concern about disease
information about SDS and its management, you can read
PPA-37: Soybean Sudden Death Syndrome in Kentucky. You
can receive a copy of this extension publication from your
county extension agent or online at:
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wet weather that prevailed for much of the growing season in
most areas was good news from the standpoint of mycotoxins.
Although mycotoxins are not a serious and widespread problem
in Kentucky, there are instances where they can cause
unacceptable levels of contamination in corn. Mycotoxins are
toxic substances produced by fungi.
mycotoxins in Kentucky are aflatoxins and fumonisins.
Aflatoxins are probably the most well-known mycotoxin, because
they have been regulated by the US. Food and Drug
Administration for the longest period of time. Fumonisons are
not as well known but are the most common mycotoxin in
Kentucky corn crops.
in general, are rare in Kentucky corn fields. Aflatoxins
require sustained drought stress and high temperatures during
grain fill. Hot, dry weather and drought stress prior to and
during silking, followed by period of high humidity, have been
associated with many outbreaks of fumonisin contamination in
corn. Given the weather experienced this growing season, we
would not expect to find aflatoxins or fumonisins in the 2003
these mycotoxins can accumulate in stored corn, if
environmental conditions permit, even if the corn was not
contaminated with mycotoxins in the field. Spores (microscopic
fungal “seeds”) of the mycotoxin-producing fungi can be
present on the outside of kernels as the grain is harvested
and stored. By themselves, the spores do not produce
significant levels of aflatoxins or fumonisins. However, if
the stored corn is held at moisture contents above 18%, spores
can germinate and grow into the corn kernels. This growth in
stored grain can result in high levels of aflatoxins and
fumonisins. There was a case from western Kentucky this past
summer of milk that had to be dumped because of aflatoxin
contamination from the 2002 crop. Thus, always be sure to
store corn properly to reduce the risk of mycotoxin buildup in
Extension resources are available on these complex subjects.
For more information, see the following:
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stored seed is a somewhat different task form protecting
stored grain/seed in the food /feed system. The same insects
attack the seed and some of the tools for prevention and
control are the same. However, several of the tools are
different and the type of protection needed is different.
two general groups of insecticides available for protection.
The first group is labeled for stored grain while the second
group is labeled for protecting the seed.
labeled for stored grain are Actellic,
Reldan and Storcide. These products
specifically seek labeling against stored products insects
such as bran bugs, weevils grain moths, etc. Actellic,
Reldan and Storcide are approved for use
on commodities that are destined for food and feed.
Formulations of Cruiser, Gaucho
and Lorsban are labeled for protecting the seed.
Most often they provide protection of the seed as it
germinates and in the small seedling stages, from insects in
and on the soil such as wireworm, aphids, seed beetles and
maggots. Cruiser, Gaucho and
Lorsban also may provide protection from stored
grain insects, but are for use on seed to be planted, not
for use on grain immediately destined for food and feed.
Managing Stored Seed/Grain
seed/grain storage manager must look closely at the intended
use of that seed/grain and whether or not that use is likely
to change. Also, the manager must decide whether or not the
seed/grain must be able to germinate or will simply be in a
bulk that needs to be protected from becoming “buggy”.
of the intended use the pesticide label must be examined
closely. Not all company claims are equal in either the list
of pests for which protection is claimed, the ease of
treatment and the level of protection.
following tips can be of help in protecting seed:
recommendations assume that the seed is initially free from
insect infestation. If the seed is infested it must be
fumigated to control existing populations then treated with
one of the seed protectants.
clean the storage area.
Use shovel, broom and vacuum cleaner. Remove all old
grain, broken pieces and grain dust from the area.
the storage area.
Tempo SC Ultra at a rate of 0.27 to 0.54 fl.
oz. (8 to 16 ml) per gal of water is a good choice for this.
Apply as a general surface, spot, crack and crevice
treatment. Tempo SC Ultra may NOT be
applied to the grain. Other insecticides may be used.
However, using a different insecticide for treating the
premises than is being applied to the seed is a good idea.
the storage area can not be adequately cleaned it may have
to be fumigated.
Thoroughly clean the seed.
Many of the most common insect pests can not live on whole,
solid kernels. Most infestations are based on broken, or
cracked kernels and dust.
applying a seed/grain protectant. If you do this follow the
quantities of seed can be stored in a cooler. Temperatures
below 50oF will prevent insect damage.
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There is a
complete service testing program for seed quality of grain
crops available to Kentucky corn, wheat and soybean producers.
This resource is the Seed Testing Laboratory of UK’s College
of Agriculture. This laboratory routinely tests seed of grain crops as well as
clovers, grasses, tobacco and vegetables. The laboratory is
located in the
Poundstone Building, Division of Regulatory Services at the
corner of University and Alumni Drives on the UK campus.
laboratory tests 150 to 200 corn samples and 500 to 700
soybean samples each year for farmers, seedsmen and other
businesses. Tests often requested on corn seed lots are
standard germination, cold test, accelerated aging, moisture
content and Roundup™ tolerance. Tests most commonly requested
on soybean lots are a complete test, standard germination,
accelerated aging, moisture content, Roundup™ tolerance and
seed count. A description of each test follows.
test includes crop purity, noxious weed and germination
evaluation of the seed lot. Crop purity includes separating
the seed sample into a pure seed component (corn or soybeans),
other crop seed (i.e. wheat or ryegrass), inert matter (broken
seeds, plant parts and insects) and weed seed (morningglory,
ragweed, or black nightshade seeds) as well as noxious weeds
(i.e. johnsongrass). This test is necessary if you plan to
label and sell your seed, as you must know and list these
components on the seed label
germination test is a measure of how many seeds are going to
sprout. Seeds for each crop are planted under optimum
laboratory germination conditions (temperature, light and
moisture). Seedlings are then evaluated to determine the
percentage of seeds that will produce a normal seedling during
a seven or eight day germination test. Thus, the germination
percentage reported is the maximum potential emergence for
that seed lot if planted in nearly ideal field conditions.
Unfortunately, field conditions are not always ideal and field
emergence may be equal to or less than the values reported for
the germination test. For this reason, some farmers and
seedsmen also conduct seed vigor tests which relate more
closely to emergence in stressful field conditions.
test is a seed vigor test routinely used for corn seed and
sometimes also used for soybean seed. When conducting this
test seeds are planted in a soil medium which contains
pathogens and are exposed to a chilling treatment (50° F) for seven days prior to exposure to warm temperatures similar to the
standard germination test. Those seeds that survive and
produce a normal seedling are more tolerant to cold stress.
Thus, seed lots with a high cold test value are better suited
to early field planting than lots with a low cold test value,
which may be damaged by cool temperatures.
accelerated aging test is another measure of seed vigor. This
test is often used for soybean seed lots and exposes seeds to
high moisture and high temperature for a short duration (i.e.
three days) prior to planting for a germination test. Seed
lots that perform well after this aging treatment are high
vigor lots and have a greater emergence potential under
stressful field conditions and greater storage potential than
low vigor seed lots.
test for Roundup™ tolerance is exactly as it sounds. The corn
or soybean seeds are exposed to Roundup™ during germination
testing and the test measures how many of the seedlings are
damaged by the herbicide. A seed lot with a low value is not
resistant to glyphosate (i.e. conventional seed lot) and a
seed lot with a high value is resistant to application of
Roundup™ (i.e Roundup Ready variety). All Roundup™ Ready
varieties should show high resistance to Roundup™ in this
content is a measure of the seed moisture percentage of a seed
lot. This information is valuable from a storage perspective.
Seed lots with a high moisture level (above 14%) should be
dried prior to storage to prevent heating and pathogen growth
that may occur, both of which can significantly damage the
quality of a seed lot.
are expressed on a per pound basis. A high seed count per
pound reflects small or light seeds and a low seed count
indicates heavier or larger seeds. This information can be
combined with results of the germination test to adjust
planting rates to maximize field emergence and stand.
laboratory charges a fee for testing seed. Prices range from
$4.00 for a seed count on any seed kind to $14.00 for a
complete test on corn. Samples can be submitted directly to
the laboratory or through your local county extension office.
A report with the test information is sent when seed testing
is completed. For a complete price list, other tests offered,
submission information or additional information about seed
testing, please contact the laboratory. Information is
available at the seed laboratory website (www.rs.uky.edu)
or you can reach the laboratory by telephone at (859) 257-2785
or by email
firstname.lastname@example.org. If you have questions regarding tests
available or meaning of the results, you are welcome to
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Most of the
articles in this newsletter focus on field issues and attempt
to provide crop management recommendations. These articles are
written by Extension faculty whom you probably have met at
various Extension meetings. Extension faculty are dedicated to
helping the Kentucky producer with current, field-based
information. However, there is another component at the
University of Kentucky who may not attend Extension meetings
but are working equally to benefit the Kentucky producer.
These individuals have a basic research focus. That means
their efforts today may not reach the field for another ten
years, but they are on the cutting edge of science.
cutting-edge scientist is Dr. Glenn Collins who is using
biotechnology to improve soybeans for Kentucky farmers. “Our
major thrust is on developing bean pod mottle virus (BPMV) and
soybean mosaic virus (SMV) resistant soybean germplasm,” Dr.
Collins said. Virus resistance is not the only area of crop
improvement as Dr. Collins continued, “We are also attempting
to genetically engineer soybeans for improved protein and oil
composition in the seeds.” A specific target for improving
protein is to improve the content of amino acids that contain
sulfur. Developing soybeans with less saturated fatty acid
content in the oil is another goal. Dr. Collins cooperates
with several field scientists to test developments in both the
laboratory and the field. Although these efforts are several
years away from reaching a producer’s field, Dr. Collins’
group is making good progress. In addition, he appreciates the
support he has received from the Kentucky Soybean Promotion
Board for this research.
Because Dr. Collins is involved heavily
in research and education, he may never appear at an Extension
meeting. However, Dr. Collins is just one example of the many
researchers in the College of Agriculture at the University of
Kentucky who are working to benefit Kentucky producers.
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In the Next Issue:
Hershman and Johnson are analyzing the data and will report on