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Drying and storage of wheat grain

After grain harvest should provide storage prior to its realization on the market or use for animal feed. After all, to realize the whole crop at once is almost impossible. The condition of the harvested wheat and type of the room in which this grain will be stored, will depend on the storage duration.

According to the materials from the source Canada Grain Council's


After grain harvest should provide storage prior to its realization on the market or use for animal feed. After all, to realize the whole crop at once is almost impossible. The condition of the harvested wheat and type of the room in which this grain will be stored, will depend on the storage duration. The binned grain varieties can be stored under condition of low temperature and room humidity. After all these are the factors that prevent or permanently delay the appearance of different insects, mites, mold and mildew. 

Storage and Cooling of Grain

Creation of conditions for grain has a single purpose - the preservation of grain quality. Low moisture content and low temperature, as mentioned above, is necessary for successful storage of grain for a long period of time. To ensure the safe storage of grain should undergo a series of processes for cooling.

Appropriate Conditions for Storage

For efficient storage of grain should comply with the appropriate conditions to prevent or obstruct the growth of microorganisms and insects. Such conditions shall include monitoring and maintenance:

- The moisture content of the grain

- Grain temperature

- Status and stability of grain

- Reserve of oxygen in the storage environment.

The Process Of Conditioning Grain Crops

The advantages of conditioning (drying)

1. Consider harvesting tough grain and thus reduces losses from weather and natural environment.

2. Increases the available harvest.

3. Possible earlier harvesting.

4. Drying tough or damp grain can reduce or eliminate spoilage of crops during storage.

5. Can improve market grade and acceptability of grain.

6. Can afford alternative market outlets for grain.

7. Can eliminate the need of stacking of the rolls for obtaining "dry" grain.

8. Can improve the quality of cologania by reducing the purification of the nucleus and cracking during combining. However, the majority of customers will not knowingly buy grain which has been artificially dried.

9. Artificially dried grain, usually contains huge amount of water, greatly overestimates the cost of production when selling.

Disadvantages of conditioning (drying)

1. Requires additional monetary investment for equipment, energy and operation.

2. Requires additional manpower. The inconvenience of processing in the absence of centralized institutions.

3. Require personnel that have experience in this field.

4. System failure (low air temperature) can degrade the quality of cologania barley.

Aeration (aeration)

Aeration - the process of ventilating stored grain at low airflow rates to maintain a fairly uniform temperature throughout the grain hopper to prevent the accumulation of moisture in the upper (or lower) section of the hopper due to the natural convection. The amount of air required to change grain temperature, can greatly affect the moisture content. Although aeration is not conditioning the grain, but in very dry weather the fan may operate for a very long time. In addition, low (1-2 liters/seconds/cubic meter) air flows are not sufficient to secure storage if grain temperature are near or below 0 °C.

Not heated or the natural drying of grain

In this system, the drying potential of ambient air used to remove moisture from the grain. The speed of drying plays an important role in obtaining the dry grain before it spoils, anyway. Usually air is blown into the hopper from the base to a fully perforated floor and out through vents on the roof. The moisture transport from the grain to the air occurs in the drying area.

Heated drying air (3 zones: the wet grain drying zone dry grain)

The principle of operation is to move the drying zone through the top of the grain mass within the allowable storage time. The time allowed for drying is reduced at high temperature and grain moisture. This means higher demand for air streams that are drying within the permissible storage for wetter grain. Similarly, when higher temperatures increase the rate of air flow to dry completely before spoilage occurs.

The effect of temperature and moisture content on allowable storage time of wheat, oats and barley.

Dry airing

Dry aeration is a modification of the system that uses the heated air followed by rapid cooling of the grain in the dryer before transfer to storage. In the process of roasting is received in the corresponding hopper or cooled. There they are stored for 8-10 hours (without air flow) and then slowly cooled. Grain can be transferred to another bin for storage. The benefits of using dry ventilation in the bunker with cooling of grain drying:

- Increased efficiency of energy

- Less risk of reducing grain quality

- Increased drying capacity due to the higher drying temperature and replacement of the cooling section additional section of the drying.

Storage in the cooling medium

The differences between storage in the cooling medium and dry airing is that when the hot grain is delivered from the dryer to cooling bins with partially perforated floors, the fan starts up immediately to avoid hardening of the grain. Quenching is eliminated, to reduce or eliminate condensation on the roof and walls. This allows you to store grain in the cooling bin, and not to transfer it to another bin for storage. Storage in the cooling medium is an interesting alternative for bins with partially perforated floors, as this allows them to be used both for cooling and for final storage.

Heated air for drying grain

Whenever the ventilation or natural air drying does not meet the conditions for grain storage, a heated air drier may be included in the system storage of the harvest. Compared with natural air drying, heated drying air absorbs more moisture from the grain and thus the grain dries faster. Of course the weight of such grain will be significantly reduced due to low moisture content in it. In addition, this grain is more expensive from the point of view of the cost of the propane. These costs must be balanced with respect to the quantity of wheat and secure the conditions of its storage.

The Drying Temperature

Some of the factors listed below, may dictate the maximum temperature for drying of cereal grains:

the storage

low temperatures should be used if storing grain for 6 months or more

- moisture

a humidifier increases the grain drying process, therefore, should be used low temperature

- type dryer

- lower temperatures should be used in dryers that are not mixed or do not distribute the grain

- the end use of the grain - malt or seed - low temperature.

The maximum safe air temperature within the dryer for barley and wheat

Since excessively high temperatures can damage the grain and reduce its ability to germinate, maximum safe air temperatures must not be exceeded.


Selection and Malting

Barley 45 °C (113 ° to 55 °C (131 ° 80-100 °C (176-212 degrees
Fahrenheit) Fahrenheit) Fahrenheit)

Wheat 60 °C (140 ° 65 °C (149 ° 80-100 °C (176-212 degrees
Fahrenheit) Fahrenheit) Fahrenheit)

The canadian Grain Commission will check the samples of grain damage caused by heated air drying. Two sample one pound (454 grams) must be submitted; one before drying and one after it. Samples must have a presentable appearance.

Drying in the Sun

Spread a thin layer of grain in open Sunny areas is a form of solar drying that has been practiced for many years worldwide, and is still running in many tropical countries. However, the drawbacks of this system are:

- The uncertainty of success due to variable weather

- Uniform grain quality.

To circumvent these problems associated with this method of drying, have been applied solar collectors in combination with a fan, a duct system and the bin in which grain is dried and stored.

Solar grain drying has been studied in Alberta as an alternative method of drying, however, was not reliable.
This was due to the high rates for the work of the collectors of grain and insufficient heating by the Sun.

Draft solar dryers grain was not as accurate as other types of dryers due to scattered, unstable and unpredictable nature of solar energy.

Types Of Grain Dryers

The main types of hot air dryers is made in the form:

- bunker
- a La carte
- Continuous flow


The basic system of the dryer hopper consists of a fully perforated floor, the grain spreader, fan and heater, sweep auger and under-floor unloading auger. In this system the grain is being loaded as a package and remains stationary in the dryer throughout the drying period. The main advantage of the dryers of this type - low installed cost.

- Offers minimum supervision.

- The suitability of the bunkers for storage after drying.

- The possibility of variable lot sizes.

Disadvantages of hand dryers-silos:

- High initial cost, which includes the processing of grain.

- The requirement of careful management in order to obtain acceptable uniform drying.

- The requirement for compliance with loading and unloading equipment.

Portion of the dryer

Batch dryers are designed as:

- without recirculation

- with recirculation

In the system without recirculation column of grain remains in the same position relative to the drying air for complete drying of the party. The grain is under dried on the outside and dried on the inner, layer. The final moisture content in the grain was determined after purification. This problem is mitigated by a recirculation batch dryer in which the grain is mixed constantly while drying using priobretennogo drill. The advantages / disadvantages of batch dryers:

- Uniformly dried grain with continuous recirculation

- The required observation

- The loss of drying time at the time the shipment is loaded or unloaded.

Dryers continuous flow

In these systems the hot air is passed through continuously smooth grain weight. After a cold hot air is blown through the grain. As the grain passes into the drying column only once, the grain is often not dried uniformly so as in the recirculating batch dryers. The advantages of continuous flow dryers:

- Continuously to dry large amounts of grain

Disadvantages of continuous flow dryers:

- Initial high cost, which comprises treating grain

- The requirement of careful management in order to obtain acceptable uniform drying.

- The requirement for compliance with loading and unloading equipment.

Storage space for

These types of spaces are designed to:

- Prevention of losses in the result of isolation from rodents, domestic animals; the requirement for a Central location;

- Protect the grain from damage due to moisture migration, snow, rainfall, heating, insects and molds;

- Ease of access with regard to the processing or inspection of grain.

Best facilities for storage are of a monolithic design of the wall shall be ventilated and be protected from bad weather conditions. The design of such premises may consist of metal or wood and regardless of the nature, they all have their advantages and disadvantages. They must be built on a high, well-dried earth, to protect grain from heavy rainfall and spring floods. Sometimes, when yields are above average, grain is stored in temporary storage, including barns, sheds or machinery in the open area.


Metal storage structures range from the shape of the round steel bins and types of arch roof with the slope of the straight walls and rectangular blocks. Round silos are most common on the canadian prairies, because they are easy to built, easy to maintain, have a wide range of sizes and can be adapted to mechanized unloading, aeration and drying systems.

The benefits of metal structures:

- fire protection

- protection against rodents

- does not require special skills in its service

- limited number of spaces for breeding insects

- full grain can be fumigated more effectively

Disadvantages of metal structures:

- for the installation of concrete slabs can cause cracks in these slabs, allowing moisture from the soil to seep into the grain itself

- expansion of storage when filled with grain, requiring waterproofing open joints.

Wooden structures

Wooden bins can be rectangular, round or have an arched roof construction. The discharge of the grain may be partially mechanized. The structure of the roof arches can be curved with the use of laminated veneer lumber, or have a gambrel roof. Mechanized unloading can be included, but it is not as comfortable as in a round storage bunker. However, the structure of the arched roof can be used as storage of equipment when not required the storage of grain.

The advantages of wooden structures:

- most of them are small, so can be moved when empty.

Disadvantages of wooden structures:

- requires constant repairs to maintain protection from the weather

- high fire risk

- low protection against rodents, unlike metal

- a large number of cracks in the wood makes it difficult to effectively control insects

Temporary storage

As mentioned earlier, when there is lack of space due to high grain yield, and for the construction of additional bunkers do not have enough money, build temporary storage.

- Open piles

Covered piles and exhaust fans

- Fencing from the snow

- Woven wire bin

- Slat bins

- Bales of straw or hay and wire connection

- Temporary bunkers out of plywood covering

- Commercially available temporary warehouses

Existing outbuildings

Fill the hopper to the top edges. Use dark polyethylene to protect the dried grain, wet grain and leave in an open area under the influence of wind and sun.

No matter what structure is used to store grain, the filling should be done in the center, as this will ensure even loading and smooth walls of the cone. Complete the granary just before the upper plate to provide a bypass for inspection and ventilation. Never store newly harvested grain on top of old grain that may be infested with insects or contain spoiled grains.

Today the bunker doing almost exclusively of metal structures with lots of space and natural air drying.

Heating Of Stored Grain

Wrong room temperature storage causes damage to the grain. As a result of increasing temperature from evaporation can form hot spots where inside the grain. The higher the moisture content and temperature of grain during storage, the greater the risk of hot spots. The heat generation is continuous and therefore constantly increasing the temperature. Continuous production of heat may result in temperatures high enough to kill microorganisms, thereby leaving the heating due to oxidation (burning without flame). At temperatures of 50 °C (122 °F) the oxidation increases the temperature so rapidly that, when left uncontrolled, spontaneous combustion can occur in a short period. Although this extreme heating effect, it can also lead to loss of ability to germinate, as well as to the poor quality of grain.

Thus heating of the grain can lead to:

- loss of ability to germinate

- loss in weight

- lower quality

- burning (in extreme conditions).

Table 2 shows the maximum levels of moisture content at which grain and oilseeds can be sold in a direct extent, as permitted in accordance with the Law of Canada on the grain.
The levels are periodically reviewed. If seeds are sold in direct the extent and the moisture levels exceed the allowable values specified in table 2, will be charged. The amount of the fine is determined by the amount of moisture content above the permitted level. Table 2 shows the safe moisture levels in grain. In practice, however, safe levels of moisture content in a one or two percentage points lower than shown in table 2.

Table 2 Maximum levels of moisture content in seeds varieties direct*.

Barley (feed) 14.8
Barley (malt) 13,5
Corn at 15.5
Buckwheat 16,0
Mustard seed 10.0
Bob garden 16.0
Flax 10.0
Lentils 14.0
Oats 13,5
Peas 16.0
Rye 14,0
Wild saffron 9.5
Soy 14,0
Sunflower 9,5
Triticale 14,0
Wheat 14.5
*Percentage based on wet weight

Factors Contributing To Storage Problems

Regardless of the determination of moisture content and temperature of grain, there are a number of other problems. The relationship between humidity and temperature can become a catalyst of new serious problems (Fig. 2). Safe shelf life can be increased by cooling the grain and reduce its moisture content. If grain was kept in severe conditions [more than 14.8 per cent (barley), 14.5 per cent (wheat), up 14.0% (triticale and oats) moisture], then every 2 weeks to check agro on the culture temperature. Usually hand stick in the mound of grain as deeply as possible or put a metal long rod at different depths to check on the warmth of the grain. Check the rod on the heat after its removal from the grain. Additional factors can contribute to the heating and spoilage of grain only in localized parts of the bin.

Migration of humidity

During storage, grain moisture it is quite uniform throughout the bunker. Over time, the limited high-humidity areas may develop due to changes in ambient temperature. Low outside temperature cools the wheat closer to the wall. This leads to a downward flow of air through the grain and upward toward the center of the bin. At the time, as the air moves through the grain, it becomes warmer and begins to pick up moisture from the grain. Condensation occurs when warm moist air hits the cool surface of the grain near the center of the hopper, which leads to the deterioration of the grain (figure 3.)

Migration of moisture in the hopper in cold weather

Reverse air flow can occur if the grain is still in storage after the end of spring. The heat from the sun on the outside of the hopper makes the flow of moisture to move in and the bunker itself through its center. High humidity, condensation occurs in the lower part of the hopper (Fig. 4). In addition, wet zones can form in the grain when rain or snow percolates through ventilators and cracks in the roofs and walls.

Migration of moisture in the hopper in warm weather.

Insects, mites and mold

Failure to protect the grain from pests can cause a great loss; not too high a price to pay? Insects, mites and molds that cause heating of grain can be cleaned by lowering the temperature (below 8 °C (48.4 °F) in insects, 3 °C (37.4°F) for mites and 8 °C (17.6 °F) for the mold). Mites and similar insects disappear at 13% grain moisture, and more adapted pests of cereals disappear when 10% moisture. Apart from the actual moisture content of the grain, its mass also affects the level of cooling.

Practical farm storage conditions are given in figure 5. The ideal condition is a humidity of 12% or less and the temperature is 3 °C or below.

Practical storage conditions in the farm

Detection of invasion

Before any control measure can be adopted, the problem must first be detected. Producing a sample of grain every 2 weeks to check for the presence of insect and the temperature, you can ensure early detection of damage.

Check for insects

You should skip the grain through a sieve to detect pests. The study sampling can help in obtaining deep samples. Other detection devices insects consist of probes or tubes, perforated with small holes that will prevent damage to the kernels but allow insects to get trapped.

Also plastic cups filled with water, can be inserted into the bunker to trap insects during the summer. In Canada there are 2 major pest of grain: rusty grain and red flour beetles. Rusty beetle lays larvae inside the grain. Adult beetle reaches a length of 0.2 cm, flat, reddish-brown. So it is diagnosed directly in the grain. Red flour beetle twice.

Check for ticks

Tick-infested samples of grain can be sifted through a sieve (12 mesh / cm; 30 / in). Dust and bran should be heated to room temperature and examined with a magnifying glass. Mites form clumps of moving dust, and so they can be found.

Control of the infestation

Before the grain is put into an empty bin for storage, it is necessary for him to spray insecticide to control any pest that might already be present (table 2).

If the pests found in stored grain, it is important to destroy them as soon as possible to keep them from spreading to other bins. Control measures depend on the conditions of grain storage, types of mites or insects, grain temperature and season of the year.

Cold weather processing

As mentioned earlier, the insects do not reproduce and do not damage the grain at 0 °C.

Fumigation of grain

Grain can be fumigated using liquid or solid fumigants. Fumigants are toxic to farm animals, people and insects, so this method should only be applied by specially trained people. Follow the instructions, and any precautions listed on the container (table 3).

Table 3. stored grain Insects

Pest and location of the Insecticide Metric measure Courses Use the Comments

EMPTY HOPPER Malathion 500 300ml/5L 10 FL oz 50% 5 l/100 m2 Apply to the internal surfaces of bunkers.
Rusty grain beetle, red EC of water/1 gallon of water (1gal/1000 ft2) will Also moisten the area beneath perforated floors
flour beetle, the weevil in the bins with vozduhonosnye system.

Treatment of stored grain fossil meals 5 kg 100 - 1000 grams/ Not more than 100 g/tonne for wheat. Death insects
and empty grain bins land bag 1 metric ton of grain occurs through dehydration almost immediately, but
Rusty grain beetle, red (diatomaceous earth) powder, depending on type, you should wait 4 weeks before mixing grain.
flour beetle, rice weevil, plants and insects
Indian moth
Mediterranean flour moths,

FUMIGATION of GRAIN IN STORAGE Phostoxin Ready Ready to Introduce tablets or wax Coated pellets prevent the release of gas within
Gastoxin the use of tablets or granules granules evenly after 4 hours the opening of the hopper. Phostoxin is a very
in tablets of grain in accordance with the toxic substance. Use it only in the event that
or granules with instructions that if the grain temperature is above 5 °C (40 °F).

The period of Fumigation Temperature the Period of Fumigation After fumigation, you should ventilate the silo for up to 48 hours or
grain: until then, until the smell to dissipate. Grain can be used
4 °C-12 °C 10 days for fodder following aeration.
12-15 °C 5 days
16-20 °C 4 days

The COLD CONTROL Rusty grain beetles and similar insects can be destroyed under the influence of low temperatures as follows:

Temperature the Time required
grain to kill insects
-5 ° for 6 weeks
-10 ° for 4 weeks
-15 ° 2 weeks

Grain temperature can be lowered by aeration.
Moving the grain several times during the cold weather can lower the temperature enough to kill insects.

Source: Kolach and McCullough, 1992.

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