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The Right Moisture to Harvest Corn

Have you ever heard of a farmer who started harvesting a corn field at 26 percent moisture and it was yielding 200 Bu./A. (adjusted to dry bushels). He left the other half of the field to dry down on its own as he went to harvest soybeans. When he harvested the other half of the corn field three weeks later it was 16 percent moisture but only yielded 190 Bu./A.?

As commodity prices decline, it is tempting to let corn dry in the field instead of harvesting early and drying it on the farm or paying drying cost at the elevator. This article discusses the three top reasons to harvest your corn between 25-20 percent moisture. Those reasons are: phantom yield loss, harvest loss, and fall operations.

Phantom Yield Loss 

This the loss of dry matter from the kernel. Seed is a living breathing organism that respires and uses its energy reserves over time. High humidity and temperature causes seed to respire at a higher rate. As seed is on the ear drying down it is in a very humid environment within the husk. Phantom yield loss is worse yet if corn dries down, is rewetted by rain and humid weather, then initiates sprouting which hurts quality, testweight and overall yield.

A Purdue study proved that yield losses of 0.6 percent-1.6 percent per point of moisture can occur in corn drying in the field(1). A later study by the University of Nebraska Lincoln minimized the significance of phantom yield loss(2). Though an elusive topic, from field trials and farmer experience and my experience, I believe phantom yield loss contributes 0.6 percent plus or minus yield loss per point of moisture and is a contributor to the yield loss observed in the field dry down of corn among other factors.

Harvest/Pre-Harvest Loss

When the corn continues to dry and die in the field there is increased butt shelling at the stripper plates and ear loss at the header during corn harvest. Stalk integrity is less so there can be more stalk and root lodging as well as ear drop prior to running the combine through the field. This all means less bushels in the grain tank and increased volunteer corn the following year and also decreased harvest efficiency which can add fuel expense and lost time. Timely corn harvest may also mean less ear mold development because ear molds enter the plant at pollination and multiply in the humid drydown conditions of grain drying in the field. 

Fall Operations

Lastly, a timely corn harvest may mean shorter lines at the elevator and more time for fall post-harvest operations such as cover crop planting, fall herbicide application, manure/fertilizer application, or fall tillage. When corn is harvested early it has more time for residue degradation which theoretically may help next year's crop. Also you can normally dry corn cheaper in early October than mid-November because you don’t need to heat the air up as much because of warmer air temperatures = less propane used per point of moisture removed.

The Math

If the elevator charges 3¢ per point of moisture per bushel (plus shrink), it would cost 21¢ per bushel to dry corn from 22 percent to 15 percent which is $42/acre at 200 bushel corn.

At $3.25/bushel corn price it takes 13 bushels to pay for drying. It is very likely in this scenario that you could lose 10+ B.U./A. bushels per acre by letting the corn dry in the field. Further reasoning to justify harvest at 25-20 percent moisture can be made by considering adverse weather/wind/rain during this time along with the other benefits mentioned above that come with a timely harvest.

In summary, plan to harvest your corn between 25-20 percent moisture this year because of phantom yield loss, harvest/pre-harvest loss, and fall operations.

For continued reading:
1. Kernel Dry Weight Loss During Post-Maturity Drydown Intervals
2. Corn Grain Yield- Kernel Weight Stability After Black Layer

What We Are Seeing On Corn Ears

Ear molds such as Gibberela and Diplodia infect the ear at pollination. We see the mold showing up at this point in season as we walk fields and husk back ears. These molds continue to multiply in the moist environment within the husk during grain maturation and drydown. We have not seen alarming amounts of ear mold yet, just scattered ears with small amounts of mold. The cool wet conditions we had at pollination may favor Giberella and Diplidia infection. This is what to keep an eye out for:

Diplodia: White mold that shows more at the butt of the ear.



Gibberela: Red-pink and white mold shows more at the tip of the ear causes vomitoxin.


Fusarium: Scattered moldy kernels and sometimes a "starburst" on the kernel causes the mycotoxin fumonisin. I'm not seeing as much of this because it is favored by hot and dry weather during and after pollination.


Kernel Red Streak: Not a mold or disease. Tip kernels sometimes have red streaks on them caused by the wheat kernel mite. Also some hybrid genetics produce kernels that are darker or have red streaks on them.


                                                (picture courtesy of

Sudden Death Syndrome (SDS)

The newsletter two weeks ago showed soybean disease identification. This week talks about management considerations for SDS.

Key considerations for SDS management:

--- Variety tolerance. Some soybeans are more tolerant of the disease than others.

--- Soybean cyst nematode population and control. Cyst nematode pressure makes SDS more likely

--- Compaction

--- Drainage

--- Later planting is less likely to contract SDS, so plant fields with a history of SDS last.
Cool, wet conditions in the early vegetative stages encourage SDS infection, which doesn't show the foliar give away until late in the summer.

--- Rotation to corn does not seem to help much.



Further reading at:

Purdue Extension - Sudden Death Syndrome

For more Agronomic News from Alex Johnson, Beck's Team Sales Agronomist, please visit his 

Agronomy Page




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