On-farm grain storage can offer growers several potential advantages: Gaining early market premiums; improved market flexibility; reduced risk of severe weather; aflatoxin reduction; early fall tillage; improved management of the farm operation, and more timely harvesting.
But, says Herb Willcutt, Mississippi State University Extension agricultural engineer, farmers must evaluate whether these advantages will help offset the costs of constructing the facilities for handling, storing, and drying the grain.
And, he says, farmers should strive for harvesting efficiency in order to insure maximum quality of grain going into storage.
“As we moved heavily into corn production the last few years, we didn’t have that much on-farm storage/drying capacity, which limited growers’ marketing flexibility,” he said at a recent grain storage workshop.
“In some years, had growers been able to dry and move corn to market to take advantage of favorable basis, they would’ve been better off financially.”
Information on storing grain in the South, with its high temperatures and humidity, “has been fairly limited,” Willcutt says.
Field drying of corn is usually the most economical approach, he notes, but adverse weather can cause harvest delays and introduce an element of uncertainty into the drydown process. “It’s a pretty cheap drying process — unless you get a hurricane or other bad weather.”
A variety maturing Aug. 1 with 33 percent moisture would be ready to harvest in eight to 13 days at a moisture content of 28 percent to 35 percent; field drying to 15 percent moisture would push the harvest date to Sept. 1.
Although modern combines can shell corn at moisture levels as high as 35 percent, he says, four years of field loss data, 1999-2002, at three locations in Mississippi, showed little advantage for harvesting high moisture content corn.
“Midwest data show that the later you get corn out of the field, the greater the losses,” Willcutt says. “Combine losses also go up extremely fast.
“These data showed the least combine losses, about 1 percent to 3 percent, when corn is at 26 percent moisture. As the grain dries, lodging gets worse, combine losses increase, and 10 percent to 15 percent loss is fairly common with corn at 15 percent moisture. These losses are due to whole ears snapping off the stalk and falling to the ground and shelling of corn in the header.”
Data from Clarksdale, Miss., combine efficiency trials showed harvesting losses of 8.6 percent to 10 percent.
“If you’re losing 2 kernels per square foot across the total width of the combine header, it equals 1 bushel per acre.”
Combine condition and adjustment are important to obtain greatest harvesting efficiency, Willcutt says. “You need to constantly be on top of adjustments for your combine to limit whole ear losses, shelling losses, and cracked corn.
“Many growers run their combines too fast; you may need to back off some on your speed in order to try and save every ear possible. A 2-3 mph combine speed is best, but too many operators are going 4-5 mph. The best thing you can do: Read your combine manual and do what it says.”
Good weed control will minimize the amount of green trash going into the combine, Willcutt says, and “a good combine operator can minimize cracked kernels and trash — a poor operator can cost you in terms of quality.”
With today’s combines, a grower can very quickly flood a grain handling/storage system, he notes. “It’s extremely easy to overload drying capacity.”
A few years ago, aflatoxin was a major problem for corn growers across the area, Wilcutt says. Aflatoxin is one of the most toxic, naturally-occurring substances for both humans and animals, and contamination can cause severe discounts or rejection of the grain at buying points.
“A late-maturing crop in high temperature/high humidity conditions and/or a drought-stressed crop are among the factors that can lead to aflatoxin development,” he says. “With the planting problems we’ve had this spring, we’re going to be seeing a lot of maturity levels this year, so growers need to be alert to conditions that could cause aflatoxin to occur. One of the best things you can do is harvest early to minimize field weathering exposure.”
As little as 25 parts per billion — just 2 kernels in a 1,250-bushel, 80 million kernels load, can spell trouble.”
Sampling for aflatoxin is highly variable, Willcutt says. “It might be detected at one elevator, not at another. One load represents a wide range of field conditions, insect pressures, fertility levels, and drought/heat stress. Contaminated kernels aren’t uniformly distributed in a load, and the ratio of infected kernels can vary across an ear.”
Contamination can spread by not cleaning equipment properly: Grain left in a combine or handling equipment, with rain, can sour and rot. The combine exterior should be cleaned daily to minimize chaff and dust that could contain aflatoxin spores.
During the last aflatoxin outbreak, Willcutt says, “People were coming into the area offering to clean contaminated corn, but you can do just as good a job with your combine in the field if you do it properly.”
Combines should be adjusted for a clean tank sample, low mechanical damage, and low losses; cleaning fans should be set for maximum speed and cleaning; and ground speed should be slowed to decrease the amount of grain being cleaned at any time.
Grain bins should be cleaned by taking the floor up and cleaning out any old grain and trash, washing the bin down with Clorox diluted 50 percent, and then pressure washing. “Once you have the problem, you need to know contamination levels that are acceptable for various markets: Feed, brewing, energy, ammoniation, etc.
“Brewers generally don’t want it because of plant cleanup problems; it can’t be used for ethanol; and while ammoniation can reduce aflatoxin, it’s not 100 percent effective and it’s bad on grain bins. If you have 20 ppb or more, federal law requires that you have an identified end user before the grain can be shipped across state lines.”
Levels acceptable in feed rations are less than 300 ppb for finishing beef; less than 200 ppb for finishing swine more than 100 lbs.; less than 100 ppb for breeding beef, swine, or mature poultry; less than 20 ppb for humans, dairy, or poultry; and less than 20 ppb when the destination at first sale is unknown.
Willcutt says growers have asked about temporary storage facilities for corn, such as shops/sheds, cottonseed houses, converted silos, storage bags, or outside storage with tarp.
For cottonseed houses, he says, corn should be stored at no more than 50 percent to 60 percent of the depth that cottonseed would be stored, and there should be a lining of plywood or steel.
“Check walls frequently for moisture migration. Typically, aeration in cottonseed houses isn’t adequate to dry corn, so put dry corn in the house. And, because of the heavier weight of corn, watch for wall deflection when filling.”
Converted silage silos should be filled only two-thirds as deep as for silage, Willcutt says. “Inspect bands and rods for corrosion and make sure handling equipment is in good condition. Using a false floor can allow for some aeration.”
If using outside storage, such as inflatable bags or piles covered with tarps, it’s important to have adequate aeration, he says.
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