This issue of Walking Your Fields newsletter contains articles about: nitrogen losses, herbicide applications and timings, planting date impact and stand evaluations. Articles are written by DuPont Pioneer agronomists in Minnesota and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. Is The Drought Over?
For many of you a defi-
nite, “Yes” is the reply.
One grower recently said
he would welcome back
a “little drought,” so he
could complete his 2013
field planting operations.
Rainfall patterns have
been extremely spotty
across the state with some areas still on the dry side. The
planting window has been extremely compressed with
only a few good working days in May. Large planters
helped many growers cover a lot of acres when they had
the opportunity. This issue of Walking Your Fields®
news-
letter will center around stand evaluation, replant deci-
sions, weed control and nitrogen management. You can
access a wide variety of agronomy topics on
www.Pioneer.com and select the “AGRONOMY” tab, also
follow us on www.Twitter.com/PioneerMN.
Now is the time to inspect fields for any planting errors
and/or where waterlogged parts of fields may have
drowned out. Pioneer®
brand hybrids are treated with four
different fungicides which should pay dividends this
spring with improved stands and better overall plant
health. Corn stands can be reduced by many issues such
as cold or wet soils, insect feeding, poor seedbed and
equipment issues. Check with your Pioneer Sales Repre-
sentative for details regarding our replant program.
Stand Evaluation & Re-plant Decisions: Re-planting
should involve a careful study of the field in question and
an analysis of its yield potential. Follow these steps:
1. Determine cause of reduced stand. Insect, disease,
environmental, etc. If you do not resolve the underly-
ing cause, such as Pythium or Black Cutworm, etc., a
second re-planting might become necessary.
2. Determine stand density and condition of the stand.
3. Estimate yield potential of reduced stand in question.
4. Estimate cost to re-plant and find out if replacement
seed is available.
5. Will re-planting pay for itself? Sometimes it‟s better to
leave the reduced stand; especially the later in to the
season it gets.
Re-planting costs time and money, and it should be done
only if the need is justified and backed up by sound deci-
sions and economics.
To determine a plant stand for row crops, take several
sample counts to represent the field or area under con-
sideration. For ease of calculation, a sample size of
1/1000 of an acre is recommended (Table 1). Measure
distance appropriate for your row width, count number of
live plants, multiply by 1000 to obtain a reasonable esti-
mate of plants per acre.
Jim Boersma
Field Agronomist
Dave Pfarr
Field Agronomist
Clyde Tiffany
Field Agronomist June 10, 2013 - Issue 3
WALKING YOUR FIELDS® newsletter is brought to you by your local DuPont Pioneer account manager . It is sent to customers several times throughout the grow-
ing season, courtesy of your Pioneer sales professional. The DuPont Oval Logo and Harmony® are registered trademarks of DuPont. PIONEER® brand products are
provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents. ®, TM, SM Trademarks and service marks of Pioneer.
© 2013 PHII.
Spring of 2013 Will Be Long Remembered
Evaluating Stands & Replant Decisions
Table 1. Row Length 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.
Table 2. Soybean Stand Reduction Loss Chart
38" 30” 15” 7.5” Plants Per
Acre
Potential
YieldNo. of plants in 10' of row
131 103 52 26 180,000 100
116 92 46 23 160,000 100
102 80 40 20 140,000 100
87 69 34 17 120,000 99
80 63 32 16 110,000 97
73 57 29 14 100,000 94
65 52 26 13 90,000 90
58 46 23 11 80,000 86
51 40 20 10 70,000 82

2. 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. Deni-
trification 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 diffi-
cult to determine. Both
of these losses occur
with the nitrate forms
of N, so the potential for significant loss is determined by
the amount of the 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 (spring vs. fall)
 The forms of N applied or expected to provide N for
the crop
 Soil characteristics
 The duration of time soils remained in a wet or satu-
rated condition like the above photo
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 most
Nitrogen losses occur when in the nitrate form, the timing
of nitrate formation is an important consideration in evalu-
ating potential losses. Fall-applied fertilizer N has a high-
er 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 anhydrous ammonia or urea are converted to nitrate-N
in about four to six weeks. Urea usually is converted to
nitrate more rapidly than anhydrous ammonia. Nitrogen
solutions (28% UAN) contain half of the N as urea and
the remainder as ammonium nitrate. Essentially, this ferti-
lizer contains 75 percent of the N as ammonium and 25
percent as nitrate when it is applied.
Options for applying supplemental Nitrogen when it is
needed include:
1. Traditional side-dressing with anhydrous ammonia or
28/32% N solutions. Where the entire crop N require-
ment has not yet been applied, side-dress or other
post-emergence applications should contain the bal-
ance of the crop N requirement plus 25-50 percent of
the N that was already applied.
2. Urea-ammonium nitrate solutions (28%) can also be
applied as a surface band or as a broadcast spray
over the growing crop.
3. Dry N fertilizers such as urea or ammonium nitrate
can also be broadcast applied to the crop. Leaf burn-
ing from solution or dry broadcast applications should
be expected. Applying the dry materials when foliage
is dry will help to minimize burning.
4. 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.
5. Under N deficient conditions, corn will respond to
supplemental N applications through the tassel stage
of development if the N can be applied.
(Source: Portions of this article are from Dr. Larry G. Bundy, U
of WI Extension Service, „Evaluating Nitrogen Losses Following
Excessive Rainfall.‟)
The days of using a total post-emerge glyphosate pro-
gram to control weeds in corn is becoming very question-
able, as there are more and more documented glypho-
sate resistant weeds appearing. As weed species be-
come more tolerant to glyphosate, growers need to use
more diversity in their weed control program. Usually this
can be accomplished by using a pre-emerge herbicide
followed by glyphosate, or glufosinate and/or by using
glyphosate or glufosinate in combination with herbicides
that provide residual broadleaf weed control.
Critical Weed-Free Period
The critical period of weed control is the interval when
weed control is required to provide maximum yield. Weed
competition before this period will not affect yield, if
weeds are controlled by the start of the critical period.
Weed competition after the critical period will not affect
yield.
Figure 1 shows weeds removed in the first four weeks
after planting, corn yield was 100 percent (solid line).
When the crop was kept weed-free for at least seven
weeks, corn yield was also 100 percent (dashed line).
It is difficult to predict the critical period, because it de-
pends upon the weeds (how competitive the different
weed species are, their density, when they emerge), and
the environment (soil moisture and nitrogen). Research
conducted on weed interference in corn indicates that
weeds should be controlled by at least the third week
Saturated soils can cause denitrifica-
tion. Photo: DuPont Pioneer
Supplemental Nitrogen Management in Corn
“The Party Is Over”
Figure 1. Source: Reprinted with permission by
Chris Boerboom, U of WI. „Timing Post-emergence
Herbicides in Corn and Soybeans.‟

3. after planting, and weed emergence should subsequent-
ly be prevented until about eight weeks after planting (or
more accurately, 14-leaf or V12 corn). Giant ragweed is a
very competitive weed species and needs to be con-
trolled before it reaches 4 inches in height.
Control Emerged, Tough-to-Kill Lambsquarters
DuPont Crop Protection has a few
products that are excellent choices
for difficult to control weeds like
lambsquarters and pigweed in soy-
beans. The active ingredient rimsul-
furon is an older chemistry but still
is an excellent tank partner along
with glyphosate and is highly effec-
tive on this weed species. Speak
with your local sales rep to learn
how DuPont®
brand Harmony®
GT
XP can help control large lambsquarters. As always, re-
member to read and follow label directions and safety
precautions.
Soybeans are „day length sensitive‟ plants. This means
flowering and maturity are triggered by the length of the
night or dark period. When adapted maturity varieties are
planted before the middle of June, the flowering is trig-
gered by shorter days (actually longer nights) after June
21. For each three to five day delay in planting, flow-
ering and maturity are delayed only about one day.
That means if you plant the same variety on May 10 and
June 10 (30 days later), the flowering and maturity of the
later planting is delayed about six to ten days. This hap-
pens regardless of the maturity of the variety.
Soybean Development
Flowering usually begins six to eight weeks after seedling
emergence and continues for three to four weeks. How-
ever, flowering will occur earlier if soybeans are planted
late. Warm temperatures
accelerate development,
especially flowering. A full
season soybean variety will
normally flower in the first
ten days of July. If there is
a hot period in mid June, it
can flower up to two weeks
earlier. When this happens,
and if there is good weath-
er for the rest of the sea-
son, higher yields result
because of the extended
reproductive period. The
soybean plant may flower
ten days earlier, but it won‟t
necessarily mature ten
days earlier because of day
length controls. Generally, yield increases as the length
of the flowering to maturity stage increases.
Warm weather in August or early September does not
hasten maturity much, unless it causes water deficit
stress. Sometimes temperature is blamed for stress, be-
cause hot temperatures often accompany drought. A cool
fall does not delay maturity much either; although yields
may be reduced if the cool weather is accompanied by
heavy rain, causing disease. The flowering period is influ-
enced more by temperature. Maturity is more strongly
influenced by photoperiod. The rapid shortening of days
starting in mid-August drives the soybean to maturity;
temperature has only a small influence on maturity.
Key Points
 Soybean maturity is strongly influenced by day length.
The rapid shortening of days in mid-August drives the
soybean to maturity; temperature has a small influ-
ence.
 Soybeans adjust their final maturity to compensate for
late planting. Delayed planting delays the onset of
flowering by only a matter of days, even when planting
is delayed for weeks.
 Even normal maturity varieties may be shorter when
planted in June. When the normal vegetative period of
six to eight weeks is shortened, the effect on the soy-
bean plant is usually reduction in height.
 Warm temperatures will induce earlier flowering and a
longer flowering period, cool temperatures will induce
later flowering and a shorter flowering period.
Planting Date Impact on Soybean
Development & Maturity
This NCGA contest has given participants the recogni-
tion 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
Enter that 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/
Photo:TomDoerge,DuPontPioneer
Photo: DuPont Pioneer

4. WALKINGYOURFIELDS®
KH Boersma, Tiffany, Pfarr
DuPont Pioneer
Sales & Marketing
PO Box 466
Johnston, IA 50131
ADDRESS SERVICE REQUESTED PRESORTED
FIRST-CLASS MAIL
U.S. POSTAGE PAID
PHI CUSTOMER INFO
Follow your DuPont Pioneer Agronomists @PioneerMN
Chad Anderson
Account Manager
Troy Elfering
Account Manager
Jay Zielske
Account Manager
Scott Hanna
Account Manager
Mark Navara
Account Manager
Reid Olson
Account Manager
Brad Weber
Account Manager
Neil Hansen
Account Manager
This Walking Your Fields® newsletter is brought to
you courtesy of your Pioneer Sales Representative
and DuPont Pioneer Account Manager.
In this issue:
 Stand Evaluations
 Nitrogen Losses
& Alternatives
 Herbicide Applications
& Timing
 Planting Date Impact