The document discusses corn drydown and harvest timing. It notes that corn planted in mid-late May or early June in the region will likely reach maturity later than usual. It also discusses factors that influence drydown rate like temperature, wind, and hybrid. The ideal harvest moisture is 22-25% but waiting until 18% risks losses from weather, stalk lodging and ear drop. Artificial drying costs vary depending on fuel prices but may increase profitability when losses are anticipated.

1. Many corn fields in the region were planted mid to late
May or early June, and that corn will likely reach maturity
(black layer) later than usual. 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 ver-
sus using artificial drying at harvest.
There are three
main factors
that influence
the rate at
which corn
dries: physio-
logical maturity,
weather, and
the corn hybrid.
Corn that ma-
tures earlier
typically dries
faster due to
more favorable
drying conditions earlier in the harvest season. Converse-
ly, 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 require only about 10-15 days to
reach 20 percent moisture, 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 air
temperature, which can be measured in Growing Degree
Units (GDUs).
Corn grain drydown rates are primarily influenced by tem-
perature. Research by Dr. Bob Nielsen, Purdue Univ.,
determined the dry down rate as affected by temperature
to be characterized by this formula:
Dry down rate =
(Average Daily Temperature X 0.0202) – 0.7133
As the following graph indicates, at an average daily tem-
perature of 85°F, corn grain would drydown about 1 per-
cent per day. At an average daily temperature of 60°F,
corn grain would dry down about 0.5 percent per day.
Factors such as wind and relative humidity will affect
these rates – drydown rates at a given temperature will
be greater under windy, low humidity conditions.
The ideal harvest kernel moisture for corn is 22 to 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.
Artificial drying costs will vary depending on LP gas pric-
es, which currently range from $1.25 - $1.40 per gallon
across Minnesota. Nonetheless, harvesting at a higher
moisture level may increase grower profitability, specifi-
cally when growers anticipate medium to high harvest
losses. The table below was developed by Iowa State
University, and customized with their permission by
DuPont Pioneer 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 DuPont Pioneer Sales
Representative.
(Sources: Minyo, Geyer & Thomison. 2009. How will delaying corn harvest affect
yield, grain quality and moisture? Ohio State University Extension. Nielsen et al.
1996. Kernel dry weight loss during post-maturity drydown intervals in corn. Pur-
due University.)
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terms and conditions of purchase which are part of the labeling and purchase documents. ®, TM, SM Trademarks and service marks of Pioneer. © 2013 PHII.
Corn Drydown and Harvest Timing
WALKING
YOUR FIELDS
®
www.pioneer.com
August 28, 2013 - Issue 5
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
Delaying harvest may increase risk of lodging,
ear drop or kernel loss and result in reduced
yields. Photo: DuPont Pioneer

2. The tillage and residue management you do this fall can
have a large influence on next year’s crop. The fall of
2013 is shaping up to be a similar environment as 2012
with dry soil conditions, which may present some of the
same opportunities and challenges. Here are some chal-
lenges and opportunities to consider during fall tillage:
Challenges of Primary Tillage in Dry Soils
 Hard, dry soil may lead to equipment stress, frequent
breakdowns, and dramatically increased wear on soil
-contacting blades and points.
 Primary tillage shanks on many brands of tillage tools
are set up on wide spacing (30”). To increase residue
coverage, many are equipped with wings on the
points. These wings on wide spacing can cause large
chunks of soil, creating undesirable seedbeds that
exhibit areas of loose dry soil intermingled with firm
moist conditions.
 To fracture the soil and form consistently sized
chunks that are field level you may need to reduce
ground speed to 4.5 to 5 mph. Each soil and type of
tillage tool is different, but slowing down may improve
the results.
Opportunities for Tillage in Dry Soil
 Primary tillage is most effective at lifting soil compact-
ed layers and producing an even shattering effect
across the width of the tillage tool.
 Soil smearing with ground contacting points is mini-
mized.
 Leveling devices on primary tillage tools may work
more effectively.
 Appropriate levels of residue incorporation can be
accomplished, which increases soil to residue con-
tact, enhancing residue breakdown without layering
residue and causing seedling residue interactions
(especially important in corn on corn rotations).
 Residue sizing and corn root ball management can
be more effective with the use of corn head choppers
or stalk choppers combined with vertical tillage tools
prior to primary tillage.
The previous photo shows variable ear placement and ear
sizes based on emergence timing and interaction of seed-
lings with residue in the developing root system. By digging
up runt plants and comparing to larger better developed
neighbors you can start to understand causes of delayed
emergence or delayed growth. Photo: Kimberly Ag Consulting. Max-
well, IA.
Pollination and grain filling are the two most critical times
in which moisture stress can impact corn yield. Here are
some points to remember:
 In areas where drought has affected the crop, corn
kernel depth will likely be shallower than normal.
 Shallow kernel depth will reduce test weight and grain
yield per acre.
 Planting dates for 2013 were later than normal, and
Growing Degree Unit (GDU) accumulations are slightly
behind the thirty year average. Physiological maturity
will likely be later than normal for most areas of East-
ern North Dakota and Northern Minnesota.
 The corn crop is mostly in the R2 to R3 stage at this
time. The following table shows the general number of
days -as well as average GDUs- that are needed to
reach physiological maturity from each stage.
Actual days between growth stages will vary depending
on daily temperatures. We often associate response to
day length with soybeans, but corn will also adjust maturi-
ty and timing of growth stages to day length to some de-
gree. GDUs alone are not a cookbook recipe for maturity
estimates. GDUs are only one tool we use to estimate the
approximate time to black layer of a hybrid, and are not a
substitute for in-field observations.
Fall Tillage in a Dry Year
Corn Development and Maturity
Large depressions from primary tillage. In this case, there
is a 12” difference between the high and the low behind the
digger. In a spring like 2012 where the conditions were dry,
this may lead to areas of dry, loose soil slumping into the
depressions in contrast to the firm moist areas. This can
lead to planter performance issues on planting depth and
seed drop due to engagement of gauge wheels, which then
leads to differing emergence rates due to seed-to-soil con-
tact and water uptake into the kernel. In a wet spring and
summer, these factors are less of a problem.
Photo: Kimberly Ag Consulting. Maxwell, IA.

3. Expected GDUs to
physiological maturity of
six Pioneer®
brand hy-
brids are listed to the
left. These values are to
be used as a guideline;
you will need to verify
these in your fields in
varying conditions,
planting dates and
stress levels.
Without knowing the actual date of a killing frost, trying to
predict when products will reach PM (black layer) in any
region would be merely a guess. An estimate could be
made based on GDU accumulations to date in your area,
the long term average GDU accumulation, and the GDUs
to PM listed by hybrid/brand above.
Drought stress during reproductive stages of soybean
causes abortion of flowers and small pods, reduced
seeds per pod and reduced seed size. The seed filling
period is particularly critical – drought stress during seed
fill results in the largest yield decreases. The table below
shows yield loss in soybeans during reproductive stages
due to drought stress. The reproductive stages of soy-
beans overlap - the first week of pod development occurs
at the same time as the second week of flowering, etc.
When a pod loses its green color, it is a sign that seed
filling has ceased in that pod. Rainfall received before
seed filling ceases will increase seed size and yields.
Drought Effects on Soybeans
Days after pollination between growth stages
and expected GDUs to Physiological Maturity (PM)
in a 80 Day Corn Hybrid
Kernel Stage of
Development
Days to
Maturity
GDUs to Reach
Phys. Maturity
R1 – Silk 50-55 850
R2 - Blister 40-45 700-800
R3 - Late Milk 30-35 500-600
R5 - Early Dent 20-25 350-450
Full Dent 10-15 150-250
R6 – Phys. Mature 0 0
Percent of Total Yield Expected When a
Killing Frost Occurs at Various Stages.
Stage
Max Grain
Yield (%)
Grain Moisture
Content (%)
Silk 0 -
Blister 0-10 85-95
Early Dent* 60-75 50-55
Full Dent* 90-95 35-40
Phys. Mat. 100 25-35
*If a killing frost does occur between early dent
and full dent, 80 to 90 percent of full yield would
still be expected.
GDUs to Phys. Mat. of
six Pioneer®
Brand Hybrids
Hybrid/
Brand1
GDUs to
PM
39D97 1840
P8210HR 1910
39V07 2020
39N95AM™ 2020
P8640AM™ 2070
P8906 2120
Effect of Four Days of Visible
Moisture Stress on Soybean Yield.
% Yield
Decrease
1st
Week Flowering 8
1st
Week Pod Development 19
2nd
Week Flowering
1st
Week of Seed Filling
3rd
Week of Pod Development 36
4th
Week of Flowering
2nd
– 4th
Week of Seed Filling 39-45
5th
Week of Seed Filling 12
Reprinted with permission by Iowa State University
1
All Pioneer products are hybrids unless designated with AM1, AM, AMRW, AMX and AMXT, in which case they are brands.
AM - Optimum®
AcreMax®
Insect Protection system with YGCB, HX1, LL, RR2. Contains a single-bag integrated refuge solution for above-ground insects. In EPA-
designated cotton growing counties, a 20% separate corn borer refuge must be planted with Optimum AcreMax products. YGCB - The YieldGard®
Corn Borer gene offers a
high level of resistance to European corn borer, southwestern corn borer and southern cornstalk borer; moderate resistance to corn earworm and common stalk borer; and
above average resistance to fall armyworm. LL - Contains the LibertyLink®
gene for resistance to Liberty®
herbicide. RR2 - Contains the Roundup Ready®
Corn 2 trait that
provides crop safety for over-the-top applications of labeled glyphosate herbicides when applied according to label directions.
Herculex®
Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex®
and the HX logo are registered trademarks of Dow AgroSciences LLC.
YieldGard®
, the YieldGard Corn Borer Design and Roundup Ready®
are registered trademarks used under license from Monsanto Company.
Liberty®
, LibertyLink®
and the Water Droplet Design are trademarks of Bayer.
Drought stress on soybeans. Note that leaves are rolled or cupped.
Photo: Rebecca Ahlers

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