As the 2013 cropping season nears completion, concerns arise about crop maturity with potential risks from early frosts impacting yields. Corn and soybean development shows varying progress across states, with yield monitoring calibration being essential for accurate data. Additionally, late-season diseases in soybeans highlight the need for proper identification to inform future management decisions.

1. As we approach the conclusion of the 2013 cropping sea-
son in our area, we’re nibbling our nails a bit. Concern
over crop maturity has many wondering if we’re in a race
to the finish line with mother nature (or even Jack Frost!)
We’re certainly going to be pushing up against a time
when killing frosts are a possibility, and with that comes
some risk of delayed maturity and potentially reduced
yields and light weight grain. In looking at how crops are
developing, the corn seems to be playing catch-up in
many areas with milk-ripe (R3) stage corn giving way to
dough stage and even some denting kernels. As of Au-
gust 19, MN reported about 27 percent of corn as dough
stage compared to a five-year average of 47 percent,
slightly behind, while SD corn was slightly ahead of the
average at 65 percent dough-stage. Both states were
near average levels for soybean pod set. Corn needs
about 200-300 GDUs (10-20 days) from 1/2-milk line
stage (dent) to reach black layer. Soybeans require about
15-18 days from R6 (filled pod at top four nodes) to physi-
ological maturity. Both crops usually require some time to
dry for ease of harvest, but a killing frost after maturity
should not affect yields or grain quality. Have a safe and
productive harvest season!
Yield data from
combine monitors
can be an im-
portant tool that
you can use to
make decisions in
your business.
However, it is only
as accurate as the
calibration, and
taking time to do
this will help elimi-
nate poor infor-
mation later. Here are some tips to remember when look-
ing at yield monitor calibration:
 Back up prior year’s data and clear memory cards
 Calibrate during the growing season as needed to en-
sure consistent data across your farm.
 Make sure your calibration loads hare heavy enough to
provide an accurate test (3,000-6,000 pounds)
 Make sure you take calibration loads at different speeds
(3.5, 4.5, 5 etc.) to simulate higher and lower yields
 Calibration loads should be in a uniform area of the
field, a good representation will improve accuracy
 Major differences in moisture and grain quality (test
weight) will require a new calibration to be accurate.
Many corn fields in the region were planted mid to late
May or early June, this corn will likely need until early Oc-
tober to reach maturity (black layer). As growers hope for
a late autumn to get field work done before the snow flies,
now is the time to weigh the cost of in-field grain drydown
versus using artificial drying at harvest.
There are three main factors that influence the rate at
which corn dries, physiological maturity, weather and the
corn hybrid. Corn that matures earlier typically dries fast-
er due to more favorable drying conditions earlier in the
harvest season. On the same note, later maturing corn
has fewer warm days to aid drying and will dry slower. In
a typical year, corn that matures on September 15 may
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Coming Into The Home Stretch!
WALKING
YOUR FIELDS
®
www.pioneer.com
August 28, 2013 - Issue 5
Growing Degree Unit Update for the Area
Location
GDU
since
May 5
Departure
from
Normal
Predicted
GDUs to 9/2
(departure)
Alexandria, MN 1688 -62 1976 (0)
Morris, MN 1762 -8 2035 (+48)
Montevideo, MN 1793 -143 2083 (-95)
Marshall, MN 1826 -75 2119 (-19)
Brookings, SD 1703 -81 2007 (+2)
Luverne, MN 1842 -74 2137 (-18)
Sioux Falls, SD 1840 -178 2146 (-133)
Source: www.pioneer.com GDU Calculator
(May 5 - August 19, 2013, forecast through Sept. 2)
Calibrating Yield Monitors
Grower enters calibration data into his yield
monitor during corn harvest. Photo: Case IH.
Corn Drydown & Harvest Timing
>>

2. require only about 10-15 days to reach 20 percent mois-
ture, while corn that matures on September 25 may need
30 days to reach the same moisture level (D.R. Hicks,
2004). Drydown is linked to heat units (GDUs). Under
ideal weather conditions, corn may lose up to one point of
moisture per day. As the days get cooler, GDUs de-
crease and drying slows. A rule of thumb is that 30 GDUs
are required to lower the grain moisture each point from
30 percent to 25 percent. Forty-five GDUs per moisture
point are required from 25 percent to 20 percent. Also
consider that we typically expect no more than about 10
GDU’s per day in late September, and only about 3-5
GDU’s per day in late October. That means that field dry-
ing of corn may take two to three times longer for late
maturing fields. Dry-down is also hybrid specific. The
amount, thickness and tightness of husks affect drydown;
the more insulated the ear, the longer it takes to dry. Up-
right ears are more prone to capture moisture in the
husks. Lastly, corn with moderate test weight dries faster
than hybrids with heavier test weight.
The ideal harvest moisture for corn is between 22-25 per-
cent. Waiting for corn to dry to 18 percent moisture in the
field certainly saves on the energy bill; but it also increas-
es the likelihood of excess harvest losses due to stalk
lodging, ear drop and detrimental weather, all of which
can affect your bottom line. In addition, there may not be
enough heat units this fall for in-field drydown. Ohio State
University research indicated no additional in-field grain
drying occurred after early to mid-November (Minyo,
Geyer & Thomison, 2009).
“Phantom yield loss” may also encourage growers to har-
vest at slightly higher moistures this fall. Growers occa-
sionally report harvesting part of a field early and finishing
the field when it is dryer, only to discover the later har-
vested portion of the field is yielding several bushels less
per acre than the first harvested corn.
Purdue University confirmed these claims indicating that
grain corn dried in the field has the potential to yield one
percent less per point of moisture. For example, corn that
was 200 bushels/acre at 28 percent moisture would only
yield around 180 bushels/acre at 18 percent moisture if
left in the field too long. This research also confirmed that
the ideal moisture level for corn grain harvest is 25 per-
cent. Harvesting wetter than that can damage kernels
and of course significantly increase drying costs (Nielsen
et al., 1996).
Artificial drying costs will vary this season depending on
LP gas prices, which currently range from $1.25 - $1.40
per gallon across Minnesota. Nonetheless, harvesting at
a higher moisture level this year may increase grower
profitability, specifically when growers anticipate medium
to high harvest losses. The table below was developed
by Iowa State University, and customized by DuPont Pio-
neer agronomists to illustrate different drying scenarios
and costs based on an average LP price of $1.35/gallon.
If you have questions about moisture levels, drydown and
harvest, contact your local sales representative for assis-
tance.
(Sources: Minyo, Geyer & Thomison. 2009. How will delaying corn
harvest affect yield, grain quality and moisture? Ohio State Univer-
sity Extension. Nielsen et al. 1996. Kernel dry weight loss during
post-maturity drydown intervals in corn. Purdue University.)
Delaying harvest may increase risk of lodging, ear drop or kernel loss
and result in reduced yields. Photo: DuPont Pioneer
Estimated Cost to Dry Corn to 15% Moisture
Harvest
Moisture
LP
gal/bu
LP
$/gal
LP
$/bu
Drying Cost
$/bu*
Drying cost
$/point*
35 0.472 1.35 0.637 0.645 0.032
30 0.337 1.35 0.455 0.461 0.031
25 0.219 1.35 0.296 0.299 0.030
20 0.109 1.35 0.147 0.149 0.030
Based on: NCH-51 Hybrid Maturity-Energy Relationships in Corn
Drying, Iowa State University; *assumes electrical cost of $0.115/kwh
Propane tanks and grain dryer set-up on bins. Photo: Mark Jeschke

3. In a stressful growing season, attack from plant patho-
gens may begin to show up late in the year as patches of
dying or wilted plants with drooping or diseased leaves.
While soybean diseases may become apparent just prior
to harvest, the infection may have occurred much earlier
in the season. These above-ground symptoms are com-
mon to several unique below-ground problems. A quick
peek at roots and lower stems can help determine which of
these pathogens might be at work in your soybean fields.
Proper identification can help with future variety selection
and management decisions.
Sudden Death Syndrome (Fusarium virguliforme)
produces striking
leaf symptoms
(Figure 1), which
alert us to problems
in the roots. Affect-
ed plants may die
rapidly after first leaf
symptoms appear
due to toxins pro-
duced by the root
rotting fungus. Split
stems will generally
show only minor
discoloration in solid
cortex areas, with
normal white pith. Cool, moisture conditions early in the
growing season often results in higher disease incidence.
Stress due to heat and drought may reduce occurrence of
SDS in some cases.
Brown Stem Rot (Phialophora gregata) produces similar
striking leaf symptoms mid-season as SDS, which may
cause confusion of the two diseases. Tissues between
veins become yellow
and quickly turn brown,
except for a narrow
band of green tissue
outlining the vein. How-
ever, BSR is distin-
guished from SDS and
other diseases by
brownish discoloration
due to an infection of
the pith tissue in lower stems (Figure 2). This infection
impedes the movement of water and mineral nutrients
needed for growth.
White Mold (Sclerotinia Rot) Sclerotinia white mold is
favored by cooler night temperatures (50-60°F) and moist
conditions in the plant canopy. In addition to cool temper-
atures, the production of white mold apothecia requires
moist soil and a closed canopy. If surface soil moisture is
low or the soybean canopy is not closed during flowering,
the fungus would not be able to produce apothecia. When
scouting for this disease, pay attention to the fields that
have a history of white
mold and fields that have
good soil moisture and a
closed canopy. The first
evidence of white mold is
a chlorotic, girdling lesion
covered with white, fluffy
mycelium at one of the
middle nodes. The evi-
dence of the disease
becomes conspicuous in
August when dead tops
start to show up in fields.
It is most likely to show
up in low spots of the
field where plant popula-
tions are high, in narrow
rows, in tightly closed
canopies, where plants
become lodged and/or where less tolerant varieties are
planted.
Northern Stem Canker (Diaporthe phaseolorum) is a re-
emergent soy-
bean disease
that begins at
points along
lower stems,
creating brown-
ish-red lesions
(cankers) ex-
tending part
way around
and into lower
stems (Figure 4). Affected plants often retain dead leaves
even up to harvest time. Roots and pith (the soft center
are of stems) are generally not affected by stem canker.
Late-Season Soybean Diseases
Figure 1. Leaf necrosis caused by SDS
or BSR. Photo: DuPont Pioneer
Figure 2. Brown stem rot.
Photo: L. Osborne, DuPont Pioneer
Figure 4. Northern stem canker.
Photo: L. Osborne, DuPont Pioneer
Figure 3. White Mold
Photo: DuPont Pioneer
AGRONOMY RESOURCES, TOOLS & APPS
Pioneer®
Field360™ Tools app
Keep fields at your fingertips
Pinpoints your field location and records notes or
photos on the spot.
Pioneer®
Field360™ Notes app
Agronomy expertise in one app in real time
Track scenarios, view precipitation map, calculate
GDUs and key crop stages.
Pioneer®
Field360™ Plantability app
This planter settings calculator gives precise
planter settings for corn and sunflower seeds of all
sizes and shapes.
Pioneer Planting Rate Estimator
Examine historical yield response curves to help
find and optimum planting rate for Pioneer®
Brand
Corn Products.

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