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Ohio State University Extension


C.O.R.N. Newsletter 2009-38

Dates Covered: 
November 10, 2009 - November 24, 2009
Greg LaBarge

How will Delaying Corn Harvest Affect Yield, Grain Quality and Moisture?-Research Findings

Leaving corn to dry in the field exposes a crop to unfavorable weather conditions, as well as wildlife damage. A crop with weak plant integrity is more vulnerable to yield losses from stalk lodging and ear drop when weathering conditions occur. Additional losses may occur when ear rots reduce grain quality and can lead to significant dockage when the grain is marketed. Some ear rots produce mycotoxins, which may cause major health problems if fed to livestock.

Several years ago we conducted a study that evaluated effects of four plant populations (24,000, 30,000, 36,000, and 42,000 plants/A) and three harvest dates (early-mid Oct., Nov. and Dec.) on the agronomic performance of four hybrids differing in maturity and stalk quality. The study was conducted at three locations in NW, NE, and SW Ohio over a three year period for a total of eight experiments. Many growers are currently weighing the risk of allowing corn to field dry. Results of this study provide some insight on yield losses and changes in grain moisture and stalk quality associated with delaying harvest. The following lists some of the major findings from this research.


• Results showed that nearly 90% of the yield loss associated with delayed corn harvest occurred when delays extended beyond mid-November.

• Grain moisture decreased nearly 6% between harvest dates in Oct. and Nov. Delaying harvest after early to mid Nov. achieved almost no additional grain drying.

• Higher plant populations resulted in increased grain yields when harvest occurred in early to mid-October. Only when harvest was delayed until mid-November or later did yields decline at plant populations above 30,000/acre.

• Hybrids with lower stalk strength ratings exhibited greater stalk rot, lodging and yield loss when harvest was delayed. Early harvest of these hybrids eliminated this effect.

• The greatest increase in stalk rot incidence came between harvest dates in October and November. In contrast, stalk lodging increased most after early-mid November.

• Harvest delays had little or no effect on grain quality characteristics such as oil, protein, starch, and kernel breakage.

In this study, yields averaged across experiments, populations and hybrids decreased about 13% between the Oct. and Dec. harvest dates. Most of the yield loss, about 11%, occurred after the early-mid Nov. harvest date. In three of the eight experiments, yield losses between Oct. and Dec. harvest dates ranged from 21 to 24%. In the other five experiments, yield losses ranged from 5 to 12%.

Grain moisture content showed a decrease from the Oct. to Nov. harvest dates but little or no change beyond the Nov. harvest dates. Grain moisture, averaged across experiments, hybrid, and plant population, decreased 6.3% points between the Oct. and Dec. harvest dates, with most of the decrease occurring between the Oct. and Nov. harvest dates (5.8 % points); only a 0.5 % point decrease occurred after early-mid Nov. Population effects on grain moisture content were not consistent. Differences in grain moisture were evident among hybrids on the first harvest date in early-mid Oct. but were generally negligible on the later dates.

For more details concerning this study, including table summaries, check out
“Effects of Harvest Delays on Yield, Grain Moisture and Stalk Lodging in Corn”. C.O.R.N Newsletter 2005-34 (October 10, 2005 - October 18, 2005); available online at

A Field Loss Calculator for Field Drying Corn
Agronomists at the University of Wisconsin have developed a “Field Loss Calculator” Excel spreadsheet available at: that allows producers to calculate the costs of harvesting today versus allowing the crop to stand in the field and harvesting later. The spreadsheet accounts for higher drying costs versus grain losses during field drying. It allows the user to account for elevator discounts and grain shrink. The following article complements this spreadsheet.

Schneider, N. and J. Lauer. 2009. Weigh Risk of Leaving Corn Stand Through Winter. University of Wisconsin Extension. Available at

Resources for A Delayed Corn Harvest

The weather over the past week has been welcomed to help progress in harvesting witha challenging 2009 corn and soybean crop. While we are making progress we still have a ways to go. Bob Nielsen, Extension Agronomist from Purdue has put together a list of resources from across the midwest that address issues related to the late harvest season including the following topics:

Maturity and Field Dry Down of Corn Grain
Frost-Damaged Crops
Grain Diseases & Mycotoxins
Harvesting Crops, Grain Drying and Storage
Feeding Issues w/ Moldy Grain
Grain Marketing & Crop Insurance
Soil Management & Tillage
Other Crop Harvest & Grain Quality Web Sites

The website can be found at

Discussing the 2009 Soybean Aphid Season and What it May Mean for 2010.

As you had read in this C.O.R.N. newsletter this past summer, soybean aphids did become a problem in parts of Ohio as predicted, with the worst problems being in the northeast counties and a few locations long Lake Erie. We did have some unusual happenings that should be mentioned again. We saw large, near economic populations in southern Ohio, especially along the Ohio River, for the first time ( We would mention that similar populations were observed in parts of Kentucky, southern Indiana, and southern Illinois.

The large flights of aphids seen in an outbreak year were much later than expected, more into mid-to-late August. These flights lasted well into the September. These late flights resulted in extremely large populations of aphids on buckthorn, the aphid’s overwintering host (C.O.R.N. Newsletter 2009-33). Having that many aphids on buckthorn is unusual during an outbreak year. We normally see high buckthorn populations during low, non-outbreak years, since these high numbers in the fall lead to our predictions of high densities the following year. Although we expected to see large egg numbers on buckthorn, this did not happen. It appeared that a fungal pathogen infected the aphid population causing significant mortality. It was not unusual to see large numbers of brown, dead unwinged aphids along with winged aphids that seemed to “melt” on the leaf surfaces. Subsequently, we have observed very few eggs on the buckthorn this fall as we had projected. We would mention that this has been the same scenario that other Midwest entomologists have seen in their states.

What does this mean for 2010? At this time, we have to admit we do not know. Normally when we see late flights and large numbers of aphids on buckthorn, we predict that we will see significant problems the following summer. But the large mortality we observed with the corresponding lack of egg deposition questions that assumption. Thus, no prediction can be made. We will recommend that growers maintain extra vigilance next summer until we see trends in what the soybean aphid population is doing. We would remind growers that this C.O.R.N. newsletter will be the best source of information as we move into the summer months during 2010. Whether the aphid remains in a 2-year cycle with 2010 having low populations, or do we lose the 2-year cycle and have economic outbreaks next year remains to be seen.

Managing Marestail and Weed Control in non-GMO Soybean Fact Sheets Available

We have a large supply of two fact sheets, “”, and “”, available at no cost. These can be viewed at our website, Our goal is to have these as widely available as possible, so let us know if you would like a quantity for your business, outlet, distribution to clientele, etc. Contact Mark Loux at 614-292-9081, or

Fall Herbicide Treatments in Wheat

There is time yet this fall to apply postemergence herbicides to wheat for control of winter annual weeds and dandelion. While winter annual weeds can be controlled with an early spring herbicide application, our research over the past 9 years or so in various crops indicates that herbicides are most consistently effective on winter annuals and dandelion when applied in fall. For most of the herbicides with activity on winter annual grasses, labels specify that control is maximized through application in fall. A dense population of winter annuals may have already suppressed wheat growth by the time a spring treatment can be applied, especially if the spring application is delayed into April. Applying herbicide and nitrogen fertilizer separately reduces the risk of injury, compared with mixtures of these applied in spring, especially when wheat is under stress from cold, wet weather in March or early April.

Many wheat herbicides can be applied in the fall, although not every herbicide label provides this information. Some labels instead indicate the minimum wheat stage before an herbicide can be applied, and our assumption has been that application in fall is allowed unless otherwise specified on the label. Wheat herbicide descriptions in the “” include this information also. In addition to tribenuron (Express, Nuance) and thifensulfuron + tribenuron premix products (Harmony Extra, Nimble, TNT Broadleaf), several newer wheat herbicides have activity on a fairly broad spectrum of winter annual broadleaf weeds. These herbicides include Huskie, Olympus, and Olympus Flex. When applied in fall, Olympus controls cheat and downy brome also, and Olympus Flex controls these grasses along with annual bluegrass and ryegrass. Among all of these herbicides, only Huskie controls ALS-resistant marestail, although dicamba (2 to 4 oz/A) can be added to the others to improve control of this and other broadleaf weeds. While we do not have as much research data on control of dandelion as we would like, our research to date indicates the most effective treatments include combinations of dicamba with tribenuron or thifensulfuron + tribenuron. Results from one study also showed Olympus Flex to have similar activity to these treatments.

We do not recommend application of 2,4-D to wheat in the fall, based on reduced yield that occurred in several studies we conducted. Most 2,4-D labels specify that it should be applied in spring after the wheat is tillering. The label for Curtail, a premix of clopyralid and 2,4-D, specifies application in spring after 4 leaves have unfolded on the main stem. The labels for several dicamba + 2,4-D premix products (WeedMaster, Brash, etc) allow application in the fall after wheat begins to tiller. However, these labels also specify that the user assumes all liability for crop injury when these products are applied in the fall.

Get Your Fertilizer Spread This Fall or Next Spring, But Avoid Frozen Ground Applications

As you continue to harvest crops, plan on getting your fertilizer down this fall prior to frozen ground setting in or plan on waiting until spring after the thaw. Considering the number of acres that did not receive phosphorus or potassium last year with the prices we were facing, some of you may be in a situation where soil test indicates that you should make the application this year. If that describes your situation there is still time to make your applications this fall. The reason we would rather see applications made this fall is because we do not want to make applications on frozen ground. Applications made to fields with any appreciable slope can result in significant fertilizer losses. Not only do these losses represent an environmental concern, but they also represent an economic loss for your operation. Remember, if you soil test levels are still above our current critical levels (60 pounds per acre phosphorus, and 175-300 pounds of potassium, depending on soil CEC) then your risk of yield loss is small. Thus, you still do not have to make an application for next summer’s crops.

Another issue that producers are bring up is our current phosphorus and potassium recommendations and critical levels. Since at least some producers avoided applications of phosphorus and potassium last year and the crop season was as successful as it has been, growers question if our recommendations are too high. The are designed to ensure that phosphorus and potassium are not limiting production based upon soil test. A soil test value below the critical does not guarantee a yield loss, so those fields with low tests that performed well may have been those instances where enough phosphorus and potassium was made available (due to chance and weather) to allow for a relatively high yield. Additionally, since no fertilizer was supplemented, we do not know how much yield could have been made with an application (some yield may have been lost, but we have no way of measuring it without non-limiting control treatments replicated in the same field). Operating on low soil test levels is a risky venture, especially with potassium. We have documented yield losses of 35% and 50% on soils with below-critical phosphorus and potassium, respectively. You may be able to produce great yields on soils with low soil test levels, but the one time you do not will be a year you will remember.

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Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.