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.)

WALKING YOUR FIELDS® newsletter is brought to you by your local account manager for DuPont Pioneer. It is sent to customers throughout the growing season, courtesy of your Pioneer sales professional. The DuPont Oval Logo is a registered trademark 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.

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

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.

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/Brand

1

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

1All 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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