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ISU Extension Logo

Northwest Iowa Extension
Crop Information
by Todd Vagts
ISU Extension Crops Specialist
Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.

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[Home][Special Topics][Weather Data][Subsoil H20][PDF Info] [ISU Extension][IA State University]
 

(Word Document)

Reducing Harvest Losses in Lodged Corn Fields
Todd Vagts
ISU Extension Field Crop Specialist

Early July wind storms flattened many west-central Iowa corn fields just prior to pollination.  Most fields recovered remarkably well by goose-necking and redevelopment of a brace root system.  Pollination and subsequent crop development has progressed without major problems, yet harvest of the goose-necked corn will be a challenge.  Rows will be difficult to follow, ears will be closer to the ground, harvest speed will be reduced and potential field losses may increase.  Depending on fall harvest conditions, stalk rots may develop, plants may fall back to the ground, and ear damage/loss may increase.  Therefore, timing of harvest, proper combine calibration, special header attachments and safety will be of up most importance.

Harvest Losses
Every bushel of corn you save by careful operation of your combine adds to your profit per acre.  Losses as high as 20 bushels of corn per acre have been measured behind a poorly adjusted combine operating in weedy or severely lodged corn.  Harvesting losses cannot be completely eliminated, but they can be reduced to 1 to 2 bushels per acre if you take time to check the performance of your combine.

To keep harvesting losses low, you need to know where losses occur, how to measure them, what reasonable loss levels are, and what machine adjustments and operating practices will reduce losses.  Checking for combine losses should take about 15 minutes. Corn saved by finding and correcting problems will more than pay for this time.

Harvest Lodged or Standing Fields First?
In most situations, it is better to harvest lodged fields or field areas before the well-standing fields. This strategy must be evaluated on a case by case basis, however. If better-standing corn is ready for harvest it may be more efficient and cost effective in some cases to harvest it first, before lodging increases there.

Where Do Losses Occur?
Until corn harvesting losses can be identified and measured, operators have no way of knowing whether their losses are at an acceptable level. Following is a list of the major sources of loss.

        Preharvest loss. Some crop losses are caused by lodging. Appearing as whole ear losses, they increase as the season progresses, and they are outside the operator's control at harvest time. Average preharvest losses should be less than 1 percent of total crop yield. This loss can go much higher in adverse crop years or when harvest is delayed.

        Header ear loss. Driving at a ground speed that is too fast or too slow, driving off the row or operating the header too high may result in lost whole or broken ears. Losses average 3 to 4 percent of the total crop yield. With proper machine operation and adjustment, you can hold losses to 1 percent.

        Header kernel loss. Some kernels are shelled out and lost by the header at the gathering snouts, snapping bars and snapping rolls. These losses average about 0.6 percent. With proper adjustment and machine operation and good field conditions, you can hold these kernel losses to about 0.4 percent.

        Combine cylinder loss. Insufficient shelling action causes some kernels to remain on the cob as they pass through the machine. With the correct cylinder or rotor speed and correct concave clearance adjustment, this loss should not exceed 0.3 percent. Correct adjustment results in few or no broken cobs with no kernels attached to them. Too vigorous shelling action results in excessive kernel breakage.

        Combine separation loss. Some kernels may pass over the sieves and out of the combine. With correct sieve and wind adjustment, this loss should be held to 0.1 percent of the total crop yield.

How To Measure Losses
To measure losses, stop your combine well in from the edges of the field, disengage the header drive, raise the header, and back up 15 to 20 feet. 

Ear Loss
Measure or pace off an area of 1/100 acre (Table 1.) on the harvested rows behind your combine, gather all missed ears of corn within this area, and count the number of equivalent 3/4-pound ears to determine total ear loss.  Each 3/4-pound ear (or its equivalent in smaller ears) found in this area is approximately equal to a loss of 1 bushel per acre.

Table 1.  Length of row(ft) for 1/100 acre for measuring ear losses

Row Width

Number of rows being harvested

(inches)

2

3

4

6

8

20

130.7

87.1

65.3

43.6

32.7

28

93.3

62.2

46.7

31.1

23.3

30

87.1

58.1

43.6

29

21.8

32

81.1

54.4

43.6

27.2

20.4

36

72.6

48.4

36.3

24.2

18.2

38

68.8

45.9

34.4

22.9

17.2

40

65.3

43.6

32.7

21.8

16.3

Kernel losses

Table 2. Dimensions of a rectangular frame enclosing 10 square feet for measuring loose kernel losses. 

Width

Length

(inches)

20

*

30

48

32

45

36

40

38

37 7/8

40

36

* Use frame for 40-inch rows and place over 2 rows at a time.

The easiest way to measure loose kernel losses is to use a rectangular frame enclosing 10 square feet.  Every 20 kernels of corn found within the frame is approximately equal to 1 bushel per acre loss. Make the frame out of No.9 wire or 1/8-inch rod and carry it on the combine. The width of the frame should be the same as the width of your corn rows, and the length of the frame is listed in table 2. 

Place the rectangular frame over the first harvested row behind the combine.  Carefully remove the stalks, husks, and leaves, and count the kernels attached to pieces of cob and the loose kernels within the frame.  Record each count separately.  Then flip the frame over onto the next row and count the kernels. After kernels are counted from all the rows being harvested, divide the total number of kernels attached to cobs by the number of rows, and then divide the answer by 20 to find cylinder loss.  Divide the total number of loose kernels by the number of rows, and then divide the answer by 20 to find the total loose kernel loss. This will be the sum of stalk roll shelling and separating loss.

 

Table 3.  Total harvest loss recording form

Row Number

Preharvest  Ear Loss

Post-Harvest Ear Loss

Cylinder Loss

Stalk Roll Shelling and Separating Loss

Total Loss

1

 

 

 

 

 

2

 

 

 

 

 

3

 

 

 

 

 

4

 

 

 

 

 

5

 

 

 

 

 

6

 

 

 

 

 

7

 

 

 

 

 

8

 

 

 

 

 

Total

 

 

 

 

 


 

What Are Reasonable Loss Levels?

Table 4. Harvesting losses for 84 randomly selected combines harvesting corn in central Iowa.

 

Average

Top 10%

 

(bu/acre)

(bu/acre)

Machine ear loss

1.5

0.0

Stalk roll shelling

0.9

0.3

Cylinder loss

0.6

0.0

Separating loss

0.7

0.2

Total harvesting loss

3.7

0.5

Preharvest dropped ears

2.1

1.0

Total loss

5.8

1.5

From randomly checked, 84 central Iowa corn combines, the average losses are listed in Table 4. Machine ear loss and stalk roll shelling were the most frequent causes of high field losses. Harvest losses were lowest when kernel moisture was between 19 and 23 percent.  If your losses are greater than the average values in table 4 stop and find out why.   

 

Tips For Keeping Losses Low
The best guide for correct combine adjustments is your operator's manual.
Remember that gathering head losses usually represent the greatest source of loss for the combine.

        Use a ground speed of 2.8 to 3.0 miles per hour.

        Close the stripper plates or snapping bars only enough to prevent ears from passing through.

        The chain flights over the stripper plates should extend beyond the edge of the plates about 1/4 inch.

        Ears should be snapped near the upper third of the snapping roll. 

        Gathering snouts should float on the ground, and gathering chains should be just above the ground.

        Measure losses and make corrective machine adjustments whenever crop conditions change.

 

Add-on Snouts and Reels
Use plastic snouts and reels to help pick up lodged corn and move it off the corn head and into the combine. Below is a list of manufactures and dealers for combine snouts and reels.

The Kelderman reel moves the corn off the header and into the combine to allow the combine to continuously move forward.

Kelderman Equipment
2686 Highway 92 East
Oskaloosa, IA 52577-9685
Phone: 800-334-6150
http://www.keldermanmfg.com


The Meteer corn reel
is very similar to the Kelderman reel. Its revolving fingers help to feed lodged corn into the head, saving down corn that would otherwise be lost.

Meteer Manufacturing
RR1 Box 221
Athens, IL 62613
Phone: 217-636-8109
http://www.meteer.com 


The Roll-A-Cone Manufacturing Company
has two different types of plastic cone attachments, one for a corn head and the other for a soybean-type head.

Roll-A-Cone Mfg. Co.
Rt. 2, Box 25
Tulia, Texas 79088
Phone: 806-668-4722
http://www.roll-a-cone.com


Soybean Platform Head May Help
If plants are extremely lodged and stalks and roots are badly deteriorated, a high number of ears may be lost over the outside snouts of a regular corn head. This is especially true if roots are easily pulled from the soil during harvest. In such cases another harvest option is to use a soybean platform head to completely cut the plants off. This may reduce the instances of corn trash plugging the head as well.

Stay Safe   
Disengage power and shut off engine before making any adjustments. Stalk rolls turn faster than you can react to release plugged stalks.  Keep shields in place.  Mechanically lock and block the corn head before getting underneath it. Carry two fire extinguishers, a small one inside the can and a 10-pound unit at ground level.

References
Profitable Corn Harvesting, 1990.  Mark Hanna and Larry Van Fossen.  PM-574, Iowa State University Extension.  http://www.ae.iastate.edu/pm574.htm

Measuring and Reducing Corn Harvesting Losses, 1993. Charles Shay, Lyle V. Ellis and William Hires.  Agricultural Publication G01290.  University of
Missouri Columbia.  http://muextension.missouri.edu/xplor/agguides/agengin/g01290.htm

Harvesting downed corn presents safety, health hazards, 2001.  John Shutske and Joseph Kurtz. University of Minnesota http://www.extension.umn.edu/extensionnews/2001/HarvestingDownedCornPresentsSafety.html

Harvesting Severely Lodged Corn, Louis Chapko.  Pioneer Hi-Bred.  Crop Insights V. 10 No. 20.  http://www.pioneer.com/usa/crop_management/corn/harvesting.htm

Corn Production Guide, A-1130, May 1997.  North Dakota State University.  http://www.ext.nodak.edu/extpubs/plantsci/rowcrops/a1130-10.htm

 

(Word Document)


Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue 
Carroll, IA 51401 
Office: 712-792-2364; Cell: 712-249-6025;  Fax: 712-792-2366
Email: vagts@iastate.edu  


For questions or comments please respond to vagts@iastate.edu

This page last updated on 07/21/03

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