Originally written February 1, 2006 | Last updated November 05, 2015

Ear Corn Storage - Cribs

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  1. Narrow cribs: 5-6 ft width - moisture % no higher than 22-23%

  2. Narrow cribs: 5-6 ft width - moisture % no higher than 22-23%

  3. Wide cribs: 7-8 ft width - moisture % no higher than 20-22%

  4. Recommended crib width is narrower in northerly areas of the CORN BELT

Dry Shell Corn Storage

A bushel of corn at 15.5% moisture consists of 47.32 pounds of dry matter and 8.68 pounds of water. 


Grain moisture is calculated on a wet basis:

Percent moisture =  100 x (wet weight - dry weight)
wet weight

When grain is dried there is less weight of dry grain:

Percent shrinkage = 1 -  { (100 - Corn moisture initial) }  x 100
(100 - Corn moisture final)

For example: 850 bushel truck load delivered at 23% moisture and is dried to 15%

1 -  { (100 - 23) }  x 100 = (1 - {77/85}) x 100% = 9.41%
(100 - 15)

Thus, the farmer would have delivered 850 bushels x 0.0941 = 80 "bushels" of water and 770 bushels of corn at 15% moisture.

Usually a 0.5% "handling" shrink is also added to "moisture" shrink due to:

  • "beeswings"

  • dust

  • general elevator experience

This would bring the total shrink to 9.41% + 0.5% = 9.91%

Many elevators use a shrink of 1.3 or 1.4 percent per point of moisture above the base market moisture. For this example:

23% - 15% = 8%
8% x 1.3 = 10.4% shrink
8% x 1.4 = 11.2% shrink

Drying and shrink charges vary by elevator and time during the season.

Typical drying charges range from 1.5 to 4 cents per point per bushel above 15% moisture.

Drying and shrink charges used by elevators often provide incentive for growers to dry their own grain.

Calculating Grain Weight Shrinkage in Corn Due to Mechanical Drying National Corn Handbook - 61

Drying Systems

Minimize moisture migration, storage diseases, and insect damage

Dry to 13% for safe, long term storage

Closed loop drying system

  1. Short bins: wet grain is dried

  2. Tall bins: dry grain is stored

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Shiver drying system

  1. Drying bin - Corn dried to 15 % moisture with forced, heated air

  2. Storage bins - Corn dried from 15 % moisture down to 13%

  3. Corn is augured from drying bins to storage bins automatically

Low temperature drying system

  • Uses unheated air or slightly-heated air

  • Depends upon outside temperature and airflow

Temperatures at which to dry corn

  • Continuous flow = 180 to 220 F

  • Corn to be used for wet milling, not exceed 140 F

  • Corn used for dry milling, not exceed 110 to 120 F

  • High temperatures reduce test weight, discolor kernels, denature protein, gelatinize starch and increase stress cracks

Recommendations for grain drying air flow by region:

The eastern and southern portions of the region need higher air flows because of higher humidities and somewhat warmer temperatures at harvest.

Hazards of Grain Drying Systems

(From MWPS-13 Grain Drying, Handling and Storage Handbook, 1987.)

A 200-lb human with a density of approximately that of water has a volume of approximately:
200 lb / (62.4 lb/cu.ft.) = 3.2 cu.ft. If the grain flow out of the bin is 1500 bu per hour, that is equivalent to 1500 bu x 1.244 cu ft/bu x 1/3600 hr/s = 0.518 cu ft/sec. So the human, if he/she is at the center of grain flow, will be buried in the grain in 3.2 cu ft/(0.518 cu ft/s) = 6.17 seconds.

Storage requirements - shell corn

Length of time depends upon temperature and humidity of grain


  1. Keep grain temp close to outside air temp 

  2. Cool with fans in late fall

  3. Warm with fans in early spring

Remove fines

  1. Worst problem in stored grain

  2. Inhibit air flow and cause heating

  3. Easiest for insects and diseases to attack

Temporary Grain Storage Tips

Picking sites that are elevated and have good drainage is the key to storing grain on the ground. The risk of crop loss is higher when grain is stored on the ground than in bins, so ground piles should be considered short-term storage and monitored frequently.

The success of storing grain on the ground depends on a combination of variables that can be controlled, such as site preparation, storage design, use of aeration and storage management, and factors that can't, such as the weather.

Advice for preventing crop loss:

  • Select a site that's elevated, has good drainage and is large enough to accommodate the volume of crop being stored and has roughly 130 feet of turnaround space for trucks dropping off the grain.
  • Prepare a pad for the grain to rest on by mixing lime, fly ash or cement in the soil to prevent soil moisture from wetting the grain. Make a concrete or asphalt pad if the site will be used for several years.
  • Create a crown in the middle of the pad with a gradual slope away from the center for water drainage. Also make sure the area around the pad drains well.
  • Run piles north and south to allow the sun to dry the sloping sides.
  • Build a retaining wall to increase storage capacity.
  • Place only cool (less than 60 F), dry, clean grain on the ground. Maximize pile size to reduce the ratio of grain on the surface, which is exposed to potential weather damage, to the total grain volume.
  • Build the pile uniformly for maximum grain surface slope and avoid creating hills, valleys, folds and crevices that will collect water.
  • Form the pile quickly and cover it immediately to minimize its exposure to moisture, wind and birds.
  • Install an aeration system to cool the grain so its temperature is uniform and equal to the average outdoor temperature. Cool temperatures minimize mold growth, limit moisture movement and control insects.
  • Check grain temperatures and moisture content at several locations in the pile every two to three weeks.
  • Frequently check the pile's cover for rodent-caused perforations, damage from wind or ice, worn spots and vandalism, and make repairs.
  • Inspect retaining walls for separation or movement at the connections and deterioration of the materials in the walls. Also make sure wall anchors still are holding.
  • When removing the grain, load it from the center of the pile to prevent uneven pressure on the retaining wall.
  • Try to separate spoiled grain from the pile to limit the amount of grain that needs cleaning, drying and blending with other grain stored in outdoor piles.

Producers also have alternatives to piling grain on the ground, such as storing grain in empty barns and pole buildings used for machinery storage. Here are some tips when using these buildings:

  • Make sure the site is well-drained.
  • Strengthen buildings to support the pressure of the stored grain. Most buildings were not designed or built to withstand any pressure on the walls.
  • Check with the building's manufacturer on how deep to fill the structure with grain.

Special Grades of Corn:

  1. Flint

  2. Flint and dent

  3. Weevily

  4. Waxy

Corn is traded on the basis of US No. 2

  1. No premiums for US No. 1

  2. Docked if below US No. 2

CORN GRADING: Grade Requirements for Corn

    Maximum limit of damaged kernels
Grade Minimum test weight per bushel Total damaged kernels Heat damaged kernels Broken corn and foreign materials
  pounds percent percent percent
U.S. Number 1 56.0 3.0 0.1 2.0
U.S. Number 2 54.0 5.0 0.2 3.0
U.S. Number 3 52.0 7.0 0.5 4.0
U.S. Number 4 49.0 10.0 1.0 5.0
U.S. Number 5 46.0 15.0 3.0 7.0
U.S. sample grade

U.S. sample grade shall be corn which:
Does not meet the requirements for the grades U.S. Numbers 1, 2, 3, 4, or 5; or   In a 1,000 gram sample, contain 8 or more stones which have an aggregated weight in excess of 0.20 percent of the sample weight, 2 or more pieces of glass, 3 or more crotalaria seeds (Crotalaria ssp.), 2 or more castor beans (Ricinus communis), 8 or more cockleburs, 4 or more particles of an unknown foreign substance(s), or a commonly recognized harmful or toxic substance(s), or animal filth in excess of 0.20 percent; or has a musty, sour, or commercially objectionable foreign odor; or is heating or otherwise of distinctly low quality.

Further Reading

MidWest Plan Service -  Available from AgriculturalEngineering Plan Service, 219A L.W.Chase Hall, University of Nebraska, 68583-0727 phone 402-472-6718. There is a charge for the publications and a fee for handling and postage.

  1. MWPS-13 Grain Drying, Handling and Storage Handbook

  2. AED-20 Managing Dry Grain in Storage

  3. MWPS-29 Dry Grain Aeration Systems Design Handbook

ISU - Indian Meal Moth

Dorn, Thomas.W. , Gerald R. Bodman, and David D. Jones. 1998. Temporary/ Emergency Grain Storage Options. University of Nebraska-Lincoln.

Herrman, Timothy J., Carl Reed, Joseph P. Harner III, and Adam Heishman.1998. Emergency Storage of Grain: Outdoor Piling. Kansas State University MF-2363 Grain Systems

Maier, Dirk E., and William F. Wilcke. Temporary Grain Storage Considerations. Purdue University

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