Originally written February 1, 2006 | Last updated October 26, 2016


rokebygrain.jpg (44475 bytes)

The safe level for ear corn in the crib is higher than for shelled corn because air passes through to remove heat and to dry the corn. In northern corn growing areas, the upper limit in narrow cribs (4 1/2 feet) is about 25% moisture in the grain. If late fall and winter are so damp that grain does not dry, spoilage will begin with the onset of warm weather in the spring. In the central Corn Belt where cribs are wider in order to handle higher yields, the safe limit is about 20%. Corn should be down to 18.5% by March 1 to avoid spoilage with the onset of warm weather.

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

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

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


  1. Estimating the Value of Wet Ear Corn--A Suggested Starting Point UWEX Bulletin A3410

  2. Usually harvested at 28-32% kernel moisture

  3. Equivalent Price/Ton of High Moisture Ear or Shelled Corn vs Price per Dry Bushel: conversion tables for converting wet ear corn and wet shelled corn to its dry corn price equivalent. Developed by Jeff Key, Winnebago County and Gary Frank, Center for Dairy Profitability

Advantages of HMEC over HMSC

  1. Can harvest 15-20% more feed/acre with HMEC than with HMSC

  2. Milk production/lb of feed is slightly better for HMEC

  3. Cows don't go off feed as often with HMEC

Advantages of HMC over conventional harvesting

  1. No Drying Costs

  2. Earlier harvest

  3. Spreads work load

  4. Reduces harvest losses

  5. HMC is more palatable than dry corn

Handling and processing of HMC for good packing and fermentation

  1. 95% of the kernels should be cracked or broken

  2. Cob pieces shouldn't be larger than 1/2-inch in diameter

  3. Grinding too fine will result in floury HMC

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

big.jpg (154734 bytes) Bin6w.jpg (119638 bytes) DryingBin.jpg (279842 bytes) callouts_150dpi.gif (72142 bytes) Mvc-008s.jpg (29843 bytes)

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

Grain Drying and Storage of Damp Grain University of Manitoba

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

Emergency/Temporary Grain Storage Considerations

Strategies for Utilizing Commodity Loan and LDP Provisions

Grain Storage:  Value, Costs, and Returns

Prepare Grain Bins and Equipment for Harvest

Initial Condition Determines Quality of Stored Grain

Grain Cleaners and Spreaders

Management - The Key to Maintaining Stored Grain Quality

Using Existing Buildings for Temporary Grain Storage

Insect Pest Management in Farm-Stored Grain

Temporary/Emergency Grain Storage Options

Computations on Grain Stored in Various Configurations

Schematic Plans and Software

Schematic Plan of a 6' by 8' Portable Bulkhead Wall

Schematic Plan of an 8' by 8' Portable Bulkhead Wall

Engineering Grain Storage and Aeration Systems

Purdue - Dryeration & Bin Cooling Systems For Grain

Purdue - Fan Sizing and Application for Bin Drying/Cooling of Grain

NDSU - Grain Drying, Part I - Introduction

NDSU - Grain Drying, Part II - Types of Dryers and Drying

NDSU - Grain Drying, Part III - Energy, Quality Fire, Moisture and Fans

NDSU - Grain Drying, Part IV - Heaters, Costs, Safety and Managing Stored Grain

Aeration Management

General Grain Quality and Storage Information

Purdue - Post Harvest Grain Quality - Stored Product Protection Program - Home page

Stored Grain Pest Management

ISU - Indian Meal Moth

U of MN - Stored-product Insects and Biological Control Agents

Ohio St - Confused and Red Flour Beetles HYG-2087-97

Ohio St - Sawtoothed and Merchant Grain Beetles HYG-2086-97

Ohio St - Granary and Rice Weevils HYG-2088-97

Uses and Quality

USDA Grading Standards and Moisture Conversion Table for Corn Purdue University AY-225

Popcorn Production and Marketing National Corn Handbook - 5

Sweet Corn Production National Corn Handbook - 43

Other publications

Aflatoxins and Other Mycotoxins National Corn Handbook - 52

Temporary Grain Storage North Dakota State University AE-84

Gib Ear Rot of Corn PDF

Costs of Drying High-Moisture Corn PDF

Shifting from Corn Drying to Corn Storage PDF

Why Is Stored Corn Deteriorating Prematurely? PDF

Grain Storage Problems Are Increasing the Dangers to Farm Operators (revised) PDF

Drying Wheat to Prevent Spoilage and Sprouting PDF

Integrating Temperature and Pest Management for Successful Grain Storage PDF

Grain Mite Infestation: Prevention and Control PDF

Proper Use of Moisture Meters PDF

Optimizing Dryer Operations PDF

Rewarming "Supercold" Grain PDF

Blue Eye in Corn PDF

Last Minute Grain Dryer Checks PDF

Slow Versus Fast Low-Temperature Bin Drying of Corn PDF

Keeping Cold Grain Cold PDF

Head Scab of Wheat and Vomitoxin PDF

Quality Grain Needs TLC PDF

Vomitoxin in Feed Wheat for Hogs PDF

Harvesting, Drying, and Storing Frost-Damaged Corn and Soybeans PDF

Cob Rot Damaged Corn PDF

Ear Corn Drying, Storage and Handling PDF

If you would like to subscribe (or unsubscribe) to updates during the growing season, click here.
©  1994-2024