Tips and Tricks of Harvesting High Moisture Grain

Submitted by Aric Koenig on Fri, 10/04/2013 - 9:34am

How to Harvest High Moisture Grain

(Applicable to John Deere 60, 70, and S-Series combines)


Complaint or Symptom:

Customer states that while harvesting high moisture field corn the machine is operating with high losses, cleaning shoe loads, tailings and may have a poor grain tank sample.



A) First step is to ensure that the concaves are leveled and zeroed. What this means is that the concaves run true to the rotor and that the concave clearance reading in the cab is accurate. This is often overlooked by customers, and can change over time and with wear. Every time concaves are replaced it is recommended that they be re-leveled and zeroed. See the Operator and/or Tech Manual for doing this work. If the measured displacement was significantly different from what was read in the cab, a concave displacement calibration may be required also. See Operator and/or Tech Manual. It is assumed that round bar concaves have been installed in the machine.


B) While checking the concave level in step A, also look at the rotor elements for excessive wear and or damage. Elements that are worn will not thresh as well as those with sharper edges. If needed, replace elements in sets of three as they are sold in the kits, doing this will maintain rotor balance.


C) The next step to confirm is the shoe settings and again confirming that the measured displacement is what the cab readout indicates. If not, adjustment is required along with a factory installation calibration. Reference the Tech Manual for proper measurement, adjustment and calibration. It is assumed that deep tooth elements have been installed in the machine.


If the above items have been checked and confirmed the next steps should be performed in the field to modify machine settings to resolve the symptom.


Start harvesting and with the recommended in cab / out of cab machine settings/adjustments, if you are still seeing the symptom perform a few good power shutdowns to determine what adjustments are required to even out the material distribution from the conveying auger bed and return pan. It's important to keep the distribution from the conveying auger bed to cleaning shoe as even as possible. When looking across the conveyor augers and front chaffer, the distribution should look like a frown with the material heavier in the middle and lighter to the outside. This way we are not decreasing the grain savings ability. You can achieve this by adjusting conveying auger bed dividers or installation of concave covers, to even out the crop load across the conveying auger bed dividers.


Issue #1: High Grain Loss, especially just inside right hand wheel track.

Cause: Excessive loading of cleaning system, tailings system, and poor distribution.


Sieve / Chaffer Settings: Run more open sieve and chaffer than for dry corn. Chaffer settings up to 22 and sieve settings up to 15 have been used successfully.

1st Step: Auger Bed Divider position: Raise up right hand (RH) divider in an effort to improve distribution away from heavy RH side loading.

2nd Step: Concave Covers. Install covers (BH84535) on #2 concave (under tailings delivery auger) to move distribution to center of cleaning system.



Issue #2: Chipped Cob in Grain Tank

Cause: Aggressive rotor / concave settings needed to thresh off tough kernels and/or spongy cob.


Grate Spacers: Install 20 mm grate spacers (H123918) on LH side of separator grates. All machines 60 Series and later have the spacers installed in the storage position (above rail). Move to space grates down. (See picture below.)


Separator Grate Spacers

H86634 Separator Grate Spacers

A - Spacers

B - Separator Grates

C - Separator Channel

Spacers are installed in storage position (as shown) from factory.

Spacers can be used in corn to reduce bits of cob in the grain tank sample and to reduce separator loss.

IMPORTANT: Spacers should be used in corn and soybeans only. Remove spacers for all other crops (place spacers in storage position as shown).

Remove all separator grate spacers (A) from storage position (as shown) and install between separator grates (B) and separator channel (C).

Spacers provide added clearance between tine ends and the separator grates allowing for cleaner grain tank samples and reduce separator loss in corn.



Concave / Rotor setting: Rule of thumb – concave “threshes”, Rotor “separates”. For loss, speed up rotor. For unthreshed, tighten concave. Run as slow of rotor and as open of concave as possible to lower loss and reduce chipped cob.

Corn Head Deck Plates: Improper deck plates can cause cob damage. Too open of deck plates allow the cob to progress deeply into the deck plates and as a result there can be cob breakage.

Feederhouse Speed: Do not run the feederhouse / cornhead any faster than needed for proper plant processing.


Issue #3: Rotor Loss

Cause: Rotor / Concave / Sieve Settings


Try to run rotor as fast as possible without damaging corn kernels.

More open concaves and higher rotor speed will reduce loss more than tight concaves and slower rotor.


Issue #4: Damaged Grain

Cause: Rotor / Concave / Sieve Settings


Concave setting: Open as far as possible (slightly more than cob diameter minimum) and still result in adequate threshing.

Rotor speed: Reduce as much as possible to get good separation.

Sieve: Tight sieve tends to cause un-needed kernel re-processing (increased tailings returns) and results in damage. Open sieve as far as possible that still allows good sample. Chaffer can be slightly tightened to reduce cob load to sieve.


Issue #5: Plugging Tailings / High Tailings

Cause: Tight sieve settings or improper distribution


Tighten chaffer to reduce cobs and leaves onto sieve

Increase cleaning fan speed reducing the amount of green leafage from the sieve, cleaning fan speeds of 1200-1300 rpm maybe required.

Open sieve (better possibility with tighter chaffer) to reduce tailings.

Concave covers (or other distribution cures mentioned earlier) to allow for better kernel processing in the front portion of the cleaning system. This will allow for grain to progress through the chaffer and sieve earlier – yielding less grain over the rear of the sieve.

Slow FAST / Feeder / Rotor / Cornhead: Slowing components down typically reduces damaged cob and broken up plant that overload the sieve and thus the tailings. Run components as slow as possible for adequate rotor separation and material handling and processing.


Issue #6: Slow Unloading

Cause: Material bridging in grain tank


Raise covers in the grain tank as high as possible. Current drive is capable of handling High Moisture Corn with open grain tank settings.

Do you still have questions or concerns about harvesting high moisture grain? The experts at Koenig Equipment can provide additional answers or recommend solutions that you may not have considered. Find the nearest location to your farm, and give us a call today. 

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