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Pre-harvest considerations for corn

When the growing season winds down, it’s time for growers to prepare for corn harvest and start thinking about next year.

Combine adjustment

Volunteer corn in soybean fields serves as a reminder to properly adjust combines.

In addition to being an eyesore, volunteer corn can cause significant economic losses by adding weed-control costs and reducing bushels at harvest.

Under normal conditions, losses due to the combine should be less than one bushel per acre. It only takes two corn kernels on the ground per square foot to lose one bushel per acre at harvest. Dropped whole and partial ears contain hundreds of kernels.

Guidance for adjusting the combine

Yield monitor calibration

Yield monitors are a valuable tool, as they provide vital data for making hybrid and maturity comparisons.

Years with moisture stress, with lower- or higher-than-normal rainfalls, likely mean more variability in grain yield and harvest moisture within and among fields. This makes a properly calibrated yield monitor even more critical.

Stalk strength

When preparing for harvest, walk through the fields to determine stalk strength. This is particularly important in fields that have experienced considerable stress.


Estimating yield

Growers can estimate yield prior to harvest using the following procedure. Accurate yield estimation requires multiple samples from representative locations throughout a field, according to a Purdue University study.


Crop maturity and early frost

Kernel moisture at the onset of denting is around 59 percent, and it generally takes an additional approximately 25 days from the start of denting to reach physiological maturity (black layer).

A light frost killing only the leaves at the half milkline stage can be expected to reduce final grain yield by 5 percent, while a hard frost killing the whole plant at this same stage would reduce final grain yield by about 10 percent.

Table 1 lists average long-term dates of critical fall temperatures for various locations in Minnesota.

Table 1: Median dates of critical fall temperatures (1948 to 2005)

Location 32°F 28°F
Northwest: Crookston Sept. 23 Oct. 2
North central: Bemidji Sept. 22 Sept. 26
West central: Morris Sept. 29 Oct. 6
Central: Stewart Oct. 1 Oct. 10
East central: Forest Lake Oct. 5 Oct. 17
Southwest: Lamberton Sept. 28 Oct. 7
South central: Faribault Sept. 29 Oct. 12
Southeast: Rochester Oct. 1 Oct. 12

Table source: Minnesota Department of Natural Resources State Climatology Office

Hybrid selection

Fall is the time to start thinking about hybrids for next spring, as success in the following year begins with decisions made in the fall.

When selecting hybrids, spread out your risk by planting multiple hybrids of differing maturity.

Identify and select hybrids that consistently are top performers over multiple sites or years within a region. Consistency over multiple environments is critical because you cannot predict next year's growing conditions.

Base hybrid selection on information from numerous sources, including universities, grower associations, seed companies and on-farm strip trials.

University of Minnesota hybrid trials

Minnesota Corn Growers Association hybrid trials

Results from the current year's trials are posted soon after harvest.

Ryan Van Roekel, former graduate student and Jeff Coulter, Extension agronomist

Reviewed in 2018

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