The corn is as high as an elephant’s eye,
An’ it looks like it’s climbin’ clear up to the sky.
You couldn’t blame motorists for wanting to break into song when they see the broad vistas of the hundreds of acres of corn farmers planted in the Delta region of the Mid-South this spring.
While the corn may not be as “high as an elephant’s eye,” in part, because of drought, the sheer number of acres makes you wonder where growers found all that seed, especially those who had to replant after an untimely Easter freeze struck the northern part of the Delta.
But many are also wondering whether producers can find a home for all that grain when they begin harvest in Louisiana later this month, followed by growers in Arkansas, Mississippi, southeast Missouri and west Tennessee in August.
Grain bin installers reportedly have been doing a land-rush business. Farmers are also looking at possibilities for temporary storage, including piling the corn on the ground, under machinery sheds, in “grain bags,” old silos and in warehouse-type buildings, including an abandoned Wal-Mart or two.
All carry some risks, especially in the Mid-South where hot, August weather can cause grain quality to deteriorate much faster than in the cooler Midwest, says Ron Noyes, professor emeritus and Extension agricultural engineer for grain storage and handling at Oklahoma State University and Purdue University.
“I’ll say right up front there is no silver bullet for storing grain,” Noyes told farmers attending a grain storage and handling workshop in Oak Grove, La., June 12. “Maybe after today you’ll have some silver buckshot to take home with you.”
Noyes is no stranger to Louisiana, having traveled to the state in 2002 to work with LSU AgCenter researchers and Extension specialists on grain storage issues. What he saw in 2002 pales in comparison to the corn Louisiana growers have planted in 2007 (730,000 acres or more than double the 300,000 acres in 2006).
The realization farmers will have a lot more grain to handle has touched off a scramble for storage from the Louisiana-Arkansas line to Cajun country in south Louisiana and back up the Red River Valley in the state’s northwest corner. (Farmers in Arkansas increased their acreage from 180,000 to 530,000 and Mississippi, 325,000 to 950,000, according to USDA’s June 29 planted acreage report.)
While many farmers are looking for any port in the storm, so to speak, where they can keep corn out of the heat and the rain, Noyes says growers must keep several things in mind whether the storage is temporary or long-term.
“There’s a technical factor called equilibrium relative humidity or ERH,” he said. “ERH is the relative humidity of the air between the kernels of grain or the air space in grain that is in equilibrium with the grain. Corn at a certain moisture content and temperature will generate a specific relative humidity in the air among the kernels.
“A level of 65 percent ERH is considered safe not only for storing corn, wheat and other grains but for other products such as fruits and nuts. For anything that can be stored in bulk, if you can keep it at 65 percent ERH or lower and take care of it in other ways, it should be safe.”
Noyes says that when grain or other commodities reach 70 percent ERH or lower, aerobic molds stop growing. “The idea is to get the grain down to where molds will not get started or grow and damage corn.”
He displayed a chart that shows 65 percent ERH can be achieved at a range of moisture from 22 percent down to 8 percent and at a range of different temperatures.
“So the moisture level at which you can store grain has a lot to do with the temperature of the crop,” he noted. “That’s why it’s important to be able to aerate and get grain cool at a certain moisture to put it in a safe condition.”
According to the ERH chart Noyes showed at the meeting, at 65 percent ERH for corn at 59 degrees F, the moisture content is 14 percent. For corn stored at 68 degrees F, the safe corn moisture is about 13.7 percent. Safe storage or 65 percent ERH for 15-percent moisture corn is 41 degrees F.
To say farmers need aeration for storage is an understatement, especially in the South, says Noyes. “In the South, my view on aeration is that it will be needed pretty darn fast after grain goes into storage. You have a limited opportunity for weather to come through and cool things down and that opportunity can move quickly.”
Steve Butzen, agronomy information manager for Pioneer, has written a publication on temporary storage of grain that has been getting increased circulation as farmers in the South and elsewhere planted more corn. Noyes distributed copies of the paper at the Oak Grove meeting.
The paper includes a chart developed by University of Nebraska researchers that shows the estimated “shelf life” for aerated, shelled corn under varying temperature and moisture conditions. (The chart is based on conditions in the Midwest that can be far from those in the south Delta.)
“Note that corn at 16 percent moisture held at a constant 50 degrees F can be safely stored six months,” says Butzen. “The shelf life decreases about one month for every point of moisture above 16 percent. At any given moisture content, shelf life is cut in half for every 10-degree F increase in temperature.”
In the hot, humid August conditions typically encountered in the South, shelf life can be drastically reduced, the chart shows. Corn stored at 16-percent moisture and at a temperature of 75 degrees could lose 0.5 percent of its dry matter after one month.
At 18 percent moisture and 75 degrees, corn begins to lose 0.5-percent dry matter in 23 days and at 20 percent moisture in 12 days.
“Corn could lose some quality at this point, but should maintain its market grade,” says Butzen. At conditions where indicated shelf life is less than one month, visible mold growth may occur sooner than the times indicated in the table.”
By now, most Mid-South farmers have realized that handling 150 to 180 bushels of corn per acre is a different ballgame than dealing with 60-bushel-per-acre soybean or wheat crops. Thus, determining how much storage is needed becomes a major undertaking.
“How much volume do I need now, and how much do I need in the future,” says Noyes. “When you’re setting up a storage system, try to plan as far in advance as you can when you start locating bins and other facilities.”
Growers should try to pick a site that fits in the traffic flow on the farm. “You need to look at traffic patterns, how you’re going to get trucks in and out. You need to set up an office space for housing moisture testers, temperature-recording and grain-sampling equipment if you have a drying system.”
One mistake many make is deciding to just dump the grain into a bin with a spout with no distribution. “A simple metal, cone-shaped spreader, for example, helps break up the fines pattern that keeps broken kernel pieces or fines, weed seed and trash from forming a dense column down the center of your storage.” (Fines can block air movement in storage.)
Another weak point in some storage bins is the roof venting — getting sufficient air openings for exhaust air to get out of the bin roof area. “You need to have adequate vents so that the air velocity through those vents from the fans is no more than 1,000 feet per minute.”
Unloading systems are important, as well. “You might start off with an augur system and put in your basic storage system first,” he said. “Then you can go back later with an elevator system or a pneumatic conveyor system.”
Aerating grain requires fans, but not just any fans. Growers must select fans that are capable of pulling a certain amount of air through the grain bin or pile or other system the grower uses for storing corn.
“If you’re only dealing with corn, large kernel grains, then you can use high-speed (3,450 rpm) vane-axial fans or low-speed (1,750 rpm), centrifugal fans,” says Noyes. “The centrifugal fans are quieter, and you can get about the same air flow with up to twice the static pressure of the vane-axial fan. If your grain isn’t too deep, the vane-axial fans will work.
“The low-speed, centrifugal fan might be the better investment, especially if you think you might be dealing with storing small grains in the future.”
He said he wants to see airflow of 0.25 cubic foot per minute per bushel (cfm/bu) in Louisiana and other parts of the South. The grain bin industry standard for the last 60 years has been 0.1 cfm per bushel.
“It takes about 130 to 150 hours of cooling time to run one cooling front through with 0.1 cfm per bushel with relatively level grain surfaces. If bins are peaked, add another 30 percent or more cooling time,” says Noyes. “You guys don’t have that kind of weather to cool for 150 to 200 hours.”
Installing airflows of 0.25 cubic foot per minute per bushel is inexpensive compared to grain losses, “and it buys you insurance to put bigger fans in, especially in corn where your static pressure is fairly low.
“So I would go between 0.25 and 0.5 cfm. With airflow rates of 0.25 to 0.5 cfm/bu, you’ll cool your corn in 30 to 60 hours. You need to watch your weather or put on an automatic controller so that when the outside air temperature drops to the desired level it will turn the system on, then when the air temperature warms above the thermostat setting, the aeration fan will turn off.”
Growers can operate their systems for three to five hours or more at a time, then wait a few days till a cool weather front comes through to run the fan again. Intermittent cooling is cumulative and is cheaper than operating the fans continuously. A fan controller will reduce costs and help maintain the grain in the right conditions.
Noyes says a grower should connect a recording hour meter in parallel with his fan so it accumulates the number of hours that the fan runs each time. “Then if you’re cooling with 0.25 cfm/bu, you’ll know when your fan has cooled for 60 to 75 hours — whatever time you decide.”
The ducting has to be integrated with the remainder of the aeration system. “Once you pick a fan capacity, you need to size the ducts, not only the solid ducts from outside that go into the perforated ducts, but aeration ducts as well. It should all be based on the total flow coming from your fans.”
Noyes said growers have several sources of information about fan selection and sizes to draw on, including a publication called “Selecting Fans and Determining Airflow for Crop Drying, Cooling and Storage,” by Bill Wilcke at the University of Minnesota. (http://www.extension.umn.edu/distribution/cropsystems/DC5716.html) .
Another is the FANS program developed by Wilcke and Dirk Maier at Purdue University (http://www.bae.umn.edu/postharvest/index.html). The latter allows growers to put in information on bin diameter and grain depth, grain type, full floor or perforated ducts,, fan manufacturer and horsepower.
“The FANS program is useful not only for setting up systems in grain bins, but also for piles, bunkers and pole barns or metal buildings with bulkheads,” said Noyes.
A paper titled, “Temporary Corn Storage Options,” distributed by Noyes at the Oak Grove meeting, provides a wealth of information on storing corn in conventional grain bins and preparing and taking care of grain in unconventional facilities such as flat storage buildings with concrete floors.
It also give pointers on converting old dairy silos for storing corn, creating wooden bulkheads for holding grain indoors and out, forming grain piles with concrete highway barriers or large hay bales for perimeter walls. A brief discussion on the use of grain bags for storage is also included. (For a copy, contact Bill Branch, Extension agricultural engineer at the LSU AgCenter in Baton Rouge or Myrl Sistrunk, West Carroll Parish, La., Extension agent, at [email protected].)
“Whether corn is stored in conventional bins, temporary structures or outside piles, it should be carefully monitored throughout the storage period,” says Noyes. “Even though temporary storage structures will likely be more difficult to check, it is even more imperative that grain in less-than-ideal storage be monitored regularly.
“Most experts suggest you should check grain at least every two weeks to assess condition and catch any problems early. If problems are detected, correct them immediately. This may require aeration, pest control or, in some cases, moving the grain.”
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