The June issue of Walking Your Fields newsletter contains articles about: Nitrogen loss after excessive rainfall, glyphosate restrictions, corn stand evaluation, and early season sunflower management. Articles are written by DuPont Pioneer agronomists in South Dakota and distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. Heavy spring rainfall causes concerns about nitrogen (N)
losses in corn fields and raises questions about the need
for supplemental N applications. In general, leaching
losses are more likely on sandy soils where water can
move through the profile quickly. Denitrification is more
likely on medium and fine textured soils that are not well
drained. The exact extent of N losses through leaching
and/or denitrification following the heavy rains is difficult
to determine. Both of these loss processes occur through
the nitrate form of N, so the potential for significant loss is
determined by the amount of the crop N supply that was
in the nitrate form when the excess rainfall occurred.
Losses depend on many factors such as when the N was
applied, the forms of N applied or expected to provide N
for the crop, soil characteristics, and soil moisture.
Where fertilizer N was applied before planting, the timing
of the application and the form of N used are important in
determining the risk of loss. Keeping in mind that losses
occur through the nitrate form of N, the timing of nitrate
formation is an important consideration in evaluating po-
tential losses. Fall-applied fertilizer N has a high risk for
loss following excess rainfall because most or all of the N
would be in the nitrate form by mid-May. For spring pre-
plant applications, ammonium forms of N such as anhy-
drous ammonia or urea are converted to nitrate-N in
about 4 to 6 weeks. Urea usually is converted to nitrate
more rapidly than anhydrous ammonia. Nitrogen solu-
tions (28% UAN) contain half of the N as urea and the
remainder as ammonium nitrate. Essentially, this fertilizer
contains 75 percent of the N as ammonium and 25 per-
cent as nitrate when it is applied.
Denitrification losses can occur within a few days if the
soil remains saturated or flooded and nitrate-N is present.
Warm temperatures and extended periods of saturated
conditions favor high losses. Work in Illinois suggests that
four to five percent of the nitrate-N present can be lost
each day the soil remains saturated. Table 1 from the
University of Nebraska provides some estimates of deni-
trification losses at various temperatures and times of
saturated soil conditions.
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Kyle Christensen
Field Agronomist
Ryan Nuttall
Product Agronomist
Jim Ruhland
Field Agronomist
June 10, 2013 - Issue 3
NCGA National Corn Yield Contest
For nearly a half century, the National Corn Grower‟s
Association‟s corn yield contest has provided corn grow-
ers an opportunity to compete with colleagues to grow
the most corn per acre ~ helping feed and fuel the world.
This NCGA contest has given participants the recognition
they deserve as well as an opportunity to learn from their
peers.
 June 15: Early entry deadline. Cost per entry $80.
 July 12: Final deadline to have all entries submitted.
Cost per entry $110
Do you have a nice looking field of Pioneer corn?
Enter a Pioneer®
brand hybrid in the yield contest and all
entry fees and membership dues are paid by Pioneer
directly to NCGA.
Talk to your Pioneer Sales Representative about
your entry.
On-line entries are available by following this link:
https://membership.ncga.com/CornyieldContest/
N Losses Following Excessive Rainfall
Continued on pg 2
Table 1. Estimated denitrification N Loss-
es as influenced by soil temperature and
days saturated.
Soil Temp
(°F)
Days
Saturated
N Loss
(% of applied)
55-60
5 10
10 25
3 60
75-80
5 75
7 85
9 95
Source: Shapiro, University of Nebraska.

2. Options for applying supplemental N when it is needed
include traditional side-dressing with anhydrous ammonia
or N solutions. Where the entire crop N requirement has
not yet been applied, side-dress or other post-emergence
applications should contain the balance of the crop N re-
quirement plus 25-50 percent of the N that was already
applied. Urea-ammonium nitrate solutions (28%) can also
be applied as a surface band or as a broadcast spray
over the growing crop. Dry N fertilizers such as urea or
ammonium nitrate can also be broadcast applied to the
crop. Leaf burning from solution or dry broadcast applica-
tions should be expected. Applying the dry materials
when foliage is dry will help to minimize burning. Basical-
ly, broadcast N rates should be limited to 90 lbs. N/acre
for corn with four to five leaves and to 60 lbs. N/ acre for
corn at the 8-leaf stage. Under N deficient conditions,
corn will respond to supplemental N applications through
the tassel stage of development if the N can be applied.
To help you assess potential fertilizer N losses, download
the simple and reliable Supplemental Fertilizer N Work-
sheet from the University of Minnesota. http://
bit.ly/17iNb9A. (Source: Schmitt and Randall, U of MN)
(Source: Portions of this article are from Dr. Larry G. Bundy, U
of WI Extension Service, „Evaluating Nitrogen Losses Following
Excessive Rainfall.‟)
Glyphosate on Corn
Corn can be damaged by
spraying glyphosate too late
in the growing season. Ears
appear to have aborted ker-
nels or scattered pollination. It
can be easy to diagnose
when only part of the field
has been sprayed. There is a
distinct line and difference
between sprayed and un-
sprayed portions of the field.
 Corn may be sprayed
broadcast or over the top
with glyphosate until it
reaches V8 stage or 30
inches in height (whichever
comes first).
 Corn can be sprayed be-
tween 30 and 48 inches
with a ground rig employ-
ing drop nozzles that direct
the spray to the base of
the corn plants and avoids
direct application of spray
solution into the whorl of
the corn plant.
Glyphosate on Soybeans
Spraying soybeans with glyphosate can occur through R2
stage. Reproductive phases are as follows:
 R1--Plants have at least one flower on any node.
 R2--Plants have at least one flower open on one of
the two uppermost nodes (Four days after R1).
 R3--A 3/16 inch pod at one of the four uppermost
nodes (Ten days after R2).
After you see the first flower, you have approximately two
weeks to spray glyphosate to stay on label. This recom-
mendation is a clarification of previous definitions of
spraying glyphosate on soybeans throughout flowering.
The average yield of corn in the U.S. and Canada has
tripled over the last half-century. Yield gains have result-
ed from improved hybrid genetics, more precise soil fertil-
ity practices, better weed control, and advances in other
production methods. Among these factors, genetic im-
provements have contributed the most to yield gains,
adding from 1.0 to 1.5 bu/acre each year. To accomplish
these increases, corn breeders have selected for superior
tolerance to drought and other stresses, and yield stabil-
ity across diverse growing environments. A key result of
enhanced stress tolerance is adaptability of hybrids to
higher plant populations. Optimum economic returns of-
ten require plant populations of 35,000 plants/acres or
more, depending on the hybrid and environment. Obtain-
ing these higher plant populations is essential, especially
at higher yield levels.
Corn stands can be reduced by many issues such as
cold or wet soils, insect feeding, poor seedbed, and
equipment issues. The best time to evaluate stands and
the effectiveness of planter equipment, residue manage-
ment and seedbed preparation is shortly after emer-
gence.
Stand counts. Take
several sample counts
to represent the field or
area under considera-
tion. For ease of calcu-
lation, a sample size of
1/1000th of an acre is
recommended (Table
2). Measure off the dis-
tance appropriate for
your row width, count
the number of live plants
and multiply by 1000 to
obtain a reasonable es-
timate of plants/acre.
Restrictions on Spraying Glyphosate
Ear on left shows irregular
kernel set resulting from a late
glyphosate application. Ear on
right is from unsprayed plant
in same field. Photo by Clyde
Tiffany, DuPont Pioneer.
Evaluate Corn Stands: Identify Areas
for Improvement
Table 2. Row lengths equal
to 1/1000th of an acre.
Row Width Length of Row
38 inches 13 ft. 9 in.
36 inches 14 ft. 6 in.
30 inches 17 ft. 5 in.
22 inches 23 ft. 9 in.
20 inches 26 ft. 2 in.
15 inches 34 ft. 10 in.
Continued from pg 1

3. Stand counts should be taken randomly across the entire
area of the field. The accuracy of your stand estimate will
improve with the number of locations sampled within the
damaged area.
Stand uniformity. Evaluate whether plants are evenly
distributed or if the stand is uneven. Gaps and doubles
indicate an equipment or seedbed problem and reduce
yield.
Identify Problems and Plan for Solutions. After you
have evaluated stands and uniformity, make every effort
to identify the causes of any observed problems. Were
metering devices working properly? Were row cleaners
set properly and working effectively? Was planting depth
proper and consistent? Was residue managed effective-
ly? Were monitors effective in identifying metering devic-
es or other equipment problems when they occurred?
Was pre-plant tillage uniform, and did it create a quality
seedbed? Continuously improve your planting operation
by making sure to implement solutions to any problems
observed.
Of all the crops grown around the world, only one was
domesticated from North America, the sunflower. Sun-
flowers are a key crop for the northern and western plains
of the U.S. In central and western South Dakota, sunflow-
ers are a great fit in the cropping rotation. Other attractive
characteristics include a relatively short growing season,
shorter than most fall crops to help spread out work load
during planting or harvest, and excellent drought toler-
ance.
Planting Depth. Proper planting depth is critical in es-
tablishing strong lateral roots for nutrient and moisture
uptake. The ideal planting depth is 1.5 to 2 inches deep,
similar to corn. The seed should be placed into moisture
but not deeper than 3 inch-
es as percent emergence
will decrease. Sunflowers
have a “woody hull” so ex-
cellent seed to soil contact
is critical and closure of the
furrow becomes more im-
portant than for corn and
most other crops.
Planting Date. Sunflowers
can be planted from May 1
until late June. Best yields are usually obtained from late
May to early June planting dates. More important than the
calendar date is having soil temperature of 50°F or more
at seed depth. 65°F is better suited for optimal germina-
tion and growth.
Scout for Early Season Insects and Weeds. Typically
the only insect to keep an eye on in the early seedling
stage is an infestation of cutworms. These caterpillar-like
larvae are usually cream color to gray-brown, often with
dark mottling or stripes as seen in photo.
Cutworms damage can be observed by chewing at, or
slightly above, ground as the plant emerges. The eco-
nomic threshold is one per square foot or 25-30 percent
stand reduction. Management options include several
different post applied insecticides that are registered for
cutworm control.
Early weed control is essential to maximizing yield poten-
tial in sunflowers. Knowing the field‟s weed history will
help plan for successful weed control options.
For emerged weeds, apply a burndown (glyphosate) in
conjunction with a residual herbicide (sulfentrazone) as a
pre-plant application. For in-season weed control, utilize
the Pioneer®
brand sunflower hybrids with the DuPont™
ExpressSun®
trait for tolerance to DuPont™ EXPRESS®
herbicide with TotalSol®
soluble granules. EXPRESS
herbicide can be applied as a post application, controlling
Canadian thistle and many other broadleaf weeds.
DuPont™, Express®
, ExpressSun®
and TotalSol®
are trademarks of DuPont or its affiliates.
Photo:TomDoerge,DuPontPioneer
Early Season Sunflower Management
Photo: NDSU Extension
Photo: NDSU Extension Entomology Department

4. WALKINGYOURFIELDS®
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DuPont Pioneer
Sales & Marketing
PO Box 466
Johnston, IA 50131
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In this issue:
 NCGA Yield Contest
 Nitrogen Management
 Spraying Guidelines
 Evaluate Corn Stands
 Sunflower Management
This Walking Your Fields® newsletter is brought to you
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DuPont Pioneer Account Manager.
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