Perils of piling grain outside
Precipitation is a big problem for uncovered grain piles, says Ken Hellevang, North Dakota State University Extension ag engineer and storage grain management specialist.
Here are some numbers to consider if piling grain outside is your plan B this year:
• Grain has a void percentage of about 43%, which means it is very porous. Water runs through it.
A 1-inch rain will increase the moisture content of a 1-foot layer of corn by 9 percentage points. This typically leads to the loss of at least a couple feet of grain on the pile surface.
• Aeration and wind blowing on the pile generally will not adequately dry the wet grain to prevent spoilage. A couple of feet of spoiled grain near the surface amounts to a huge loss.
A cone-shaped pile 25 feet high is approximately 59,000 bushels of grain. Losing just 1 foot of grain on the surface is about 13% of the grain, and a loss of $39,000, if the grain value is $4 per bushel. A pile 60 feet high will have a diameter of about 250 feet and hold about 800,000 bushels.
Losing 1 foot of the surface grain is a loss of only about 6% of the grain, but it has a value of about $176,600 at $4 per bushel. A cover to prevent water infiltration is strongly recommended.
• Drainage is of critical importance to the success of any grain storage. There will be about 25,000 gallons of water running off a 100-by-400-foot area during a 1-inch rain. This water must quickly run away from the grain and the area next to the grain.
Examine the entire area to ensure that flooding of the site will not occur during major rain events.
• The ground-piling surface of an outdoor pile needs to be prepared to prevent moisture from reaching the grain. The storage floor should be higher than the surrounding ground to minimize moisture transfer through the soil into the grain.
The ground surface should be crowned so any moisture that does get into the pile drains to the exterior, rather than creating a wet pocket that leads to grain deterioration. Use lime, fly ash, cement, or asphalt to prepare the ground surface.
• Grain covers are held in place by a combination of restraining straps and suction from the aeration system. For a vacuum to be formed within the pile, access to air by the aeration system must be restricted. However, adequate airflow through the grain must be provided to control grain temperature.
Perforated ducts are placed on the grain under the cover to provide a controlled air intake for the aeration system, and to provide airflow near the cover to minimize condensation problems under the cover. A perforated wall should permit airflow through the grain, but the amount of open area needs to be minimal so the air does not “short-circuit” to the fan.
Wind velocity will determine the amount of suction needed to hold the cover in place. Some control systems measure wind velocity and start fans based on the wind speed.
Backup power may be used to ensure that the cover is held down during power outages. Check the backup power to assure that it starts when needed.
• Grain should be cooled with aeration to reduce the potential for insect infestations.
Insect reproduction is reduced at temperatures below about 60 degrees F; insects are dormant below about 50 degrees F; and insects can be killed by extended exposure to temperatures below about 30 degrees F.
Cooling grain as outdoor temperatures cool also will reduce moisture migration and the potential for condensation near the top of the grain pile. The rate of mold growth and grain deterioration is affected by both the grain moisture content and the temperature.
The allowable storage time is approximately doubled with each 10-degree-F reduction in grain temperature. For example, the allowable storage time for 17% moisture corn is about 130 days at 50 degrees F, and about 280 days at 40 degrees F.
The grain should be cooled whenever the average outdoor temperature is 10 to 15 degrees cooler than the grain temperature, and cooled to near or below 30 degrees F for winter storage depending on available air temperature.
• Wind does not aerate a grain pile because the airflow takes the path of least resistance, which is over the grain pile rather than through the grain.
• Aeration ducts need to have perforations sized and spaced correctly to have air uniformly entering or exiting the duct, and to obtain the desired airflow through the grain.
Ensure that the ducts are appropriately connected and secured so the duct placement is correct after filling.
Space aeration ducts equal to the grain depth to achieve acceptable airflow uniformity. Fans need to be sized to both aerate the grain and hold down the pile cover.
Source: NDSU Extension
This article published in the October, 2014 edition of DAKOTA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2014.