General Information on Grain Drying, Storage and Management
Grain drying, storage and management is a critical issue to Missouri producers. Much of the profit or loss of farming can result from decisions that the producer makes after harvest. Missouri's temperate climate requires that producers who store grain be continually aware of its condition. The uncertainty of market prices provides opportunity to reap a profit or realize a loss merely from storing grain. Harvest time activities, coupled with the proximity of local commercial grain elevators, makes on-farm storage a necessity for many Missouri producers.
Stored Grain Management
Grain storage, particularly in temperate climates such as Missouri, requires a few simple management practices to ensure that the grain remains 'in (good) condition' as the seasons change. The best strategies are to inspect grain weekly, especially when air temperatures change quickly, and to aerate grain as needed to avoid storage problems. Measure and record grain temperatures in the bin center and about two feet below the grain surface. Watch for sudden increases in temperature or temperature differences in the grain mass and aerate as needed to maintain uniform grain temperatures.
Recognizing the causes of storage problems is the first step in good grain storage management. Storage problems arise from combinations of several factors including poor initial grain quality, moisture migration, storage molds and insects.
Poor Initial Grain Quality
Poor grain quality is a flag that should signal the need for more intensive inspection procedures. An intact seed coat protects the living embryo of a seed while physically damaged seeds are vulnerable to mold development and insect invasion. Aerated corn or soybeans in good physical condition can typically be stored safely until spring at wet basis moisture contents of 15.5% and 14%, respectively. Corn and soybeans should be dried to 14% and 12%, respectively, for storage up to one year. If any physical damage has occurred, inspect grain often and reduce all storage moisture levels by at least 1% below target levels for safe storage.
Moisture migration is another primary cause of storage problems. Moisture migration results from convective air currents caused by differences between the grain temperature and average outside air temperature. These differences in temperatures between outside air and the grain mass occur in the fall as average outside air temperatures drop and in the spring when average ambient air temperatures rise.
The importance of the effect is most significant in the fall. As outside temperatures drop, grain near the bin walls becomes cooler. The air in the grain becomes cooler and denser. The dense air moves downward and into the warmer grain in the center of the bin. This once cool air is then warmed by the grain in the center and becomes lighter, rising to the surface of the grain and carrying moisture. Moisture condenses on the cool grain at the surface. This wetter grain is more susceptible to attack by fungi and insects.
Managed aeration is the solution to preventing moisture migration. Begin aeration when the temperature difference between the ambient air and the grain mass is approximately 15°F. Continue aeration until the entire grain mass reaches an equilibrium temperature.
Once aeration is started, fans should be operated continuously until a complete cycle is detected by observing a somewhat abrupt change in the temperature of the grain surface or the exhaust air. Two or three cycles may be needed for the grain to reach an equilibrium temperature. This is particularly true when warming the grain in the spring. The warm air will initially condense moisture onto the grain just in front of the warming zone. If aeration stops before the warming zone moves completely through the grain (one cycle), condensed moisture will remain in the grain and provide conditions favorable for fungi and insects.
Several species of mold-causing fungi are always involved when grain becomes spoiled. By the time the obvious symptoms of fungal infections occur, considerable deterioration has already occurred. Left unchecked, a succession of fungi will emerge, each comfortable in a relatively small range of temperatures, but causing further increases in temperature. Toward the upper extremes, thermophilic fungi may cause temperatures of 140-149°F. They may be followed by thermophilic bacteria that can cause temperatures above 167°F. Under some conditions, chemical processes can occur which cause temperatures high enough for spontaneous combustion.
The incidence of storage molds and insects can typically be prevented or reduced by exercising strict cleaning and sanitation of bins, augers and other facilities and by keeping the grain at proper moisture and temperature conditions.
Storage molds can be controlled by quickly reducing grain moisture to below 15% and following the target moisture content levels previously set forth. Use seasonal aeration to reduce or eliminate moisture migration and to prevent wet pockets of grain that provide favorable conditions for fungi. Weekly inspection can help prevent irreversible conditions that can claim a whole bin of grain. Aerate grain immediately if any of the following conditions are noticed:
- musty or spoiled grain odor;
- hard layer or core below the grain surface;
- warm grain below the top surface;
- wet or slimy grain at the surface from moisture migration; and
- condensation on the roof that drips onto the grain.
Economics of Grain Storage
Storage of grain should be a conscious business decision based on the overall farm management plan. Aspects of the farm management plan that impact whether or not to store grain are:
- marketing plans, especially the anticipation of a better price for the grain at a later date;
- feeding the grain to livestock at a later date;
- transportation and labor constraints during harvest; and
- taking advantage of government programs.
Two options exist for storing grain. The first is on-farm storage, the second is commercial storage.
On-farm storage usually requires the purchase of storage facilities, which are then available for use for many years. However, on-farm storage can be rented from neighbors or landowners.
The advantages of on-farm storage include: 1) avoid selling the grain at seasonally low harvest time prices; 2) easier and quicker transportation of grain from the field to storage facilities; 3) allows the producer to harvest grain at a higher moisture level and to condition the grain on the farm without receiving a high discount from commercial elevators; and 4) gives marketing flexibility.
The disadvantages of on-farm storage include: 1) cash costs of purchasing and maintaining storage facilities; 2) concern with maintaining grain quality; 3) additional grain handling compared to commercial storage; 4) weight loss due to shrink; 5) risk of loss due to losing condition, rodent and insect infestation and natural disasters, and 6) owning on-farm storage results in a fixed cost (taxes, insurance, depreciation and interest on investment) regardless of whether or not grain is stored.
A producer incurs both fixed and variable costs when storing grain in good condition . The fixed, or ownership, costs are the largest costs. Hence, the most significant decision concerning on-farm storage is whether or not to purchase storage facilities.
Once facilities are purchased, the wise management of stored grain is a relatively small cost. Running an aeration fan continuously for several days may seem expensive, but aeration costs for an entire season typically amount to only a fraction of a penny per bushel. Drying corn one additional point to increase storage life causes grain shrinkage of about 2/3 pounds. Estimated drying costs for removing moisture is 2 cents per point per bushel. A serious infestation can quickly offset the costs of drying grain to proper levels and the costs of using seasonal or periodic aeration to control moisture migration.
The largest variable cost of grain storage is the opportunity cost of (foregone interest on) the value of the grain. An alternative investment rate of 10% on corn which could have been sold for $3/bushel but was stored for four months incurs an opportunity cost of 10 cents per bushel.
Costs not incurred if grain is sold at harvest or stored in commercial facilities are the cost of additional handling associated with on-farm storage and the risk of losing grain to infestations of fungi and insects.
The advantages of commercial storage include: 1) opportunity to sell the grain at any time without incurring additional handling expenses, 2) shifting the risk of loss of condition and natural disaster to the elevator and 3) depending on location, commercial storage may allow quicker transportation and unloading time than on-farm storage.
The disadvantages of commercial storage include: 1) higher cash costs than on-farm storage, 2) incur a cost of taking the grain out of storage to feed it to cattle or to sell it to someone other than the elevator, 3) risk of the elevator going bankrupt and leaving the producer as an unsecured creditor and 4) the shrink associated with drying usually exceeds true shrinkage of the grain.
Note: This paper is a part of the Missouri System of Crop Production, Extension Manual 165. Call 800-292-0969 to order a copy of the complete manual.
- MU Guide 1310 - Low-Temperature, In-Bin Drying.
- MU Guide 1305 - Estimating Airflow for In-Bin Grain Drying Systems.
- MU Guide 1300 - Low-Profile Bins for Grain Drying.
- MU Guide 1969 - Safe Storage and Handling of Grain.
- EC 960 "Grain Storage Management: A Guide for Keeping Your Grain in Top Condition. Brooker, D.B., F. W. Bakker-Arkema, and C. W. Hall. 1992.
- "Grain Conditioning Technology" - an educational aid prepared by Behlen Manufacturing Company, Columbus, NE.
- Drying and Storage of Grains and Oilseeds. Van Nostrand Reinhold, New York, NY. Loewer, O.J., T.C. Bridges,, and R. A. Bucklin. 1994.
- On-Farm Drying and Storage Systems. American Society of Agricultural Engineers, St. Joseph, MI.
Back to Missouri Grain Storage