Yield information from monitors and yield maps is an extremely important tool that you can use to make deci-sions in your business. However, it is only as accurate as the calibration and taking time to do this will help elimi-nate poor information later. Here are some tips to remem-ber when looking at yield monitor calibration:

Clear your memory card and back up previous year’s data

Calibrate multiple times throughout the growing sea-son to ensure consistent data

Make sure your load is enough weight (3,000-6,000 pounds)

Make sure you have multiple loads at different speeds (3.5, 4.5, 5 mph, etc.)

Calibration loads should be in a uniform area of the field, a good representation will improve accuracy

Differences in moisture and grain quality will require a new calibration to be accurate

In a year with variability, taking time to calibrate will pay big dividends!

Many corn fields in the region were planted mid to late May or early June, which means a lot of corn will likely need until early October 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 har-vest. 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. Similarly, 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 heat units (GDUs). Under ideal weather conditions, corn may lose up to one point of moisture per day. As the days get cooler, GDUs decrease

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 GDUs per day in late September, and only about 3-5 GDUs per day in late October. That means that field drying of corn may take two to three times longer for late maturing fields. Drydown is also hybrid specific. Long, tight husks as well as hybrids of high test weight tend to dry slower than hy-brids that don’t carry those characteristics. 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

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.

Calibrating Yield Monitors

WALKING YOUR FIELDS

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August 28, 2013 - Issue 5

Corn Drydown & Harvest Timing

Delaying harvest may increase risk of lodging, ear drop or kernel loss and result in reduced yields. Photo: DuPont Pioneer

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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 har-vest is 25 percent. Harvesting wetter than that can dam-age kernels and of course significantly increase drying costs (Nielsen et al., 1996). Artificial drying costs will vary this season depending on LP gas prices. Nonetheless, harvesting at a higher mois-ture level this year may increase grower profitability, spe-cifically when growers anticipate medium to high harvest losses. The table below was developed by Iowa State University, and customized by DuPont Pioneer agrono-mists to illustrate different drying scenarios and costs based on an average LP price of $1.35/gallon.

(Sources: Minyo, Geyer & Thomison. 2009. How will delaying corn har-vest affect yield, grain quality and moisture? Ohio State University Ex-tension. Nielsen et al. 1996. Kernel dry weight loss during post-maturity drydown intervals in corn. Purdue University.)

What is the ideal harvest moisture for corn grain? Or, to be more specific, what grain moisture will provide the greatest economic return to the grower? This is a question that has been studied and debated over the years, with some growers favoring earlier har-vesting, while others prefer drier grain to minimize artifi-cial drying. While there is no definitive answer to this question, limited research, and some reliable on-farm anecdotes suggest grower’s yield may “disappear” after physiological maturity due to respiring grain in the field. (a.k.a. phantom yield loss) Additionally, field and harvest loss due to ear drop and shelling may also impact har-vestable yield. To address this question, DuPont Pioneer is looking for growers to run a simple test in their field this fall, compar-ing a “early harvest” vs. “late harvest.” The test is easy to do, and can be done with any corn hybrid: 1. Select a uniform field near bins or buildings that allow

for multiple harvests over time. 2. Harvest a portion of the field early, with grain mois-

tures near 25%.

3. Harvest a second time (or more) a week or more lat-er, with final grain moisture targeted less than 20%.

4. Record harvest data with a yield monitor or weigh wagon.

5. Note visible yield loss (dropped ears, etc.) 6. Provide harvest dates, yield & moisture data and

notes to your Sales Rep or DuPont Pioneer Agrono-mist.

Contact your local Pioneer Sales Representative if you are willing to participate in this test and to answer any questions you may have. Again, we are looking for lots of grower participation to help us address this question.

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 patho-gens might be at work in your soy-bean fields. Prop-er identification can help with fu-ture variety selec-tion and manage-ment decisions.

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

Early Harvest Challenge Late-Season Soybean Diseases

Figure 1. Leaf necrosis caused by SDS or BSR. Photo: DuPont Pioneer >>

Prevent Plant Acres Management

Sudden Death Syndrome (Fusarium virguliforme) produces striking leaf symptoms (Figure 1), which alert us to problems in the roots. Affected plants may die rapidly after first leaf symptoms appear due to toxins produced 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 diseas-es. Tissues be-tween veins be-come yellow and quickly turn brown, except for a narrow band of green tissue out-lining the vein. However, BSR is distinguished

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 ad-dition to cool tempera-tures, the production of white mold apothecia requires moist soil 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 evidence of the dis-ease becomes conspicu-ous 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 populations are high, in nar-row rows, in tightly closed canopies, where plants be-come lodged and/or where less tolerant varieties are planted. Northern Stem Canker (Diaporthe phaseolorum) is a re-emergent soybean disease that begins at points along lower stems, creating brownish-red lesions (cankers) ex-tending part way around and into lower stems (Figure 4). Affected plants often retain dead leaves even up to har-

vest time. Roots and pith (the soft center are of stems) are generally not affected by stem canker.

The challenging weather from this spring left a large amount of acres unplanted in some areas of Wisconsin. As a result, we are encountering fields that have a tre-mendous amount of weed pressure. Annual weeds such as giant ragweed, common lambsquarter, pigweed, and waterhemp are all prolific seed producers. If left uncon-trolled giant ragweed can produce 5000-10,000 seeds per plant and common lambsquarter, waterhemp, and pigweed are all capable of producing 100,000 seeds per plant. The effects from not controlling these weeds can potentially have long term effects from a weed control standpoint. According to studies, it can take 12 years to reduce a common lambsquarter weed seed bank by 50 percent, due to factors such as seed dormancy. It will also be extremely important to evaluate your weed con-trol program on these acres for next season. There could be some early pressure from winter annual weeds like shepherd's-purse and dandelions that will require a fall or spring burn down. In addition, it will be very important to have a good foundation herbicide program in place for these acres next spring; not controlling this early weed pressure could have a significant impact on yield.

Figure 4. Northern stem canker. Photo: L. Osborne, DuPont Pioneer

Figure 2. Brown stem rot Photo: L. Osborne, DuPont Pioneer

Figure 3. White Mold Photo: DuPont Pioneer

Heavy shepherd’s-purse and common lambsquarter pressure in pre-vent plant field. Photo: Brian Buck, DuPont Pioneer

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