Correspondent
MADISON
What are the risks of leaving this year’s high-moisture corn standing in the field during part or all of the winter in hopes that it will dry to an acceptable level for safe storage? What about the possibility of harvesting that corn as soon as possible for snaplage instead? What concerns could there be when feeding this year’s corn to dairy cattle?
Those questions and others are considered in a series of advisories issued in late October by the University of Wisconsin Extension’s TeamGrains. The full versions of all the releases are posted on the Web site: http://fyi.uwex.edu/grain.
Based on back-to-back winters starting in 2000 and 2001 at the Arlington research station, the results of leaving corn stand for part or all of the winter could be radically different, according to Winnebago County agriculture agent Nick Schneider. Due mainly to a heavy snow cover, the yield losses topped 50 percent for the crop grown in 2000 and didn’t even reach 20 percent for the test plots for the 2001 crop during a winter with little snow.
Schneider says the pertinent question for growers is whether the winter loss will be less than the cost of drying the corn that would be harvested in the next few weeks. There is no definite way to predict how much the yield loss would be but the variable factors include stalk strength, ear health, insect damage and shank attachment plus the possibility of wildlife damage and the totally unpredictable amount of snowfall, ice cover or winter rainfall, he points out.
The Extension has prepared a break-even table based on the percent of yield loss during the winter, drying costs and per bushel corn prices. For example, the break-even drying cost would be 56 cents per bushel for corn worth $3.75 per bushel if the anticipated yield loss would be 15 percent. At a 40 percent loss, growers would break even by spending up to $1.60 per bushel for drying if the corn were sold for $4 per bushel.
One source estimates a cost of 40 cents per bushel for drying corn by 10 moisture points – $80 per acre on a 200-bushel yield or $60 for a 150-bushel yield. Schneider notes that, for many growers, the 2009 corn crop was already the most expensive that they ever grew.
Wisconsin’s corn growers who had crop insurance also need to be aware that their coverage for a crop harvested for grain ends on Dec. 10, Schneider states. This means they could not make claims on a crop harvested later but they should still contact their insurance agent before the deadline to talk about options if they plan to leave their corn stand into the winter, he advises.
While research data shows that the corn is likely to dry to below 20 percent moisture by late winter or early spring, growers will face the challenge of preparing the fields for the next crop after a very late harvest, Schneider observes. Other risks are higher pest populations and volunteer corn in the following crop, he adds.
While combines can comfortably handle corn that’s between 20 and 30 percent moisture, this changes with corn above 30 percent moisture, Extension machinery systems specialist Matthew Digman reminds growers. “Then your work will be a balancing act between leaving unthreshed grain in the field and grain damage.”
When harvesting wet corn, adjust the ground speed to avoid overloading the combine engine which will need to operate at its rated speed to keep the separator and cleaning shoe running at full speed, Digman advises. Set the header as high as possible and consider widening the stripper plates on the deck to reduce the volume of wet plant material that could easily interfere with the proper operation of the separator, he adds.
Consult the operator’s manual for adjusting the combine’s concave to a uniform alignment and appropriate clearance, Digman continues. “But first make sure it is level side-to-side on a conventional combine or front-to-back on a rotary combine.”
Then adjust the cylinder or rotor speed for maximum threshing of the wet grain in combination with an acceptable amount of grain damage, Digman notes. “If there’s too much grain damage, slow the cylinder or rotor. Don’t increase the concave clearance.”
With the cleaning shoe, start with the maximum chaffer and sieve openings specified in the operator’s manual and adjust based on how clean the corn coming into the tank is, the amount of cob in the grain and the volume of tailings sent for rethreshing, Digman indicates. If there’s too much cob, try increasing the airflow first and then close the top chaffer sieve a little or the lower shoe sieve a little to address the problem, he suggests.
Above all, have the combine in good repair for operating under such trying conditions, Digman emphasizes. He encourages checking the operator’s manual and with the local dealer to learn if there are any equipment options or inserts for harvesting very high-moisture corn as grain.
To avoid most of those potential problems and challenges, harvesting corn as snaplage when the kernels have at least 28 percent moisture is still a practical option for many corn growers, TeamGrains suggests. For that, the team referred to an article written by Bill Mahanna, a corn and livestock nutrition specialist who is affiliated with Iowa State University and Pioneer Hi-Bred.
Mahanna defines snaplage as corn harvested with a silage chopper equipped with a snapper head and run through the chopper’s kernel processor. Snaplage contains kernels, cobs and some husks and ear shanks. It differs from high-moisture ear corn because the latter is picked and then processed through a roller mill or tub grinder at the storage structure rather than in the chopper’s processor, he explains.
Snaplage brings such advantages as a harvest between corn silage and dry grain, yields 10 to 15 percent higher than with dry grain, a potential cost saving compared to processing at the storage structure, higher availability of starch in the rumen compared to dry corn and having the cobs and non-kernel material add fiber to the ration, Mahanna indicates. As disadvantages, he lists fermentation and feedout losses, a higher inventory carrying cost and inconsistency in starch digestibility because of changes over time while in storage.
The inclusion of corn cobs will raise the moisture of snaplage to an ideal of about 34 to 35 percent moisture when going into storage, Mahanna indicates. He recommends inoculating the snaplage with Lactobacillus buchneri if it is not going to be fed until the spring or summer and, as with corn silage, not starting to feed it until 60 days after it went into storage, although it probably completed fermentation in two to three weeks if the kernel moisture was above 28 percent.
With snaplage and high-moisture and dry shelled corn, however, there could easily be feeding risks for dairy cattle with corn from the 2009 crop, Wisconsin’s Extension livestock nutritionists point out in another of the series of advisories. They explain that the higher, much higher in many cases, moisture content in grain corn translates to lower starch content, a faster rate of starch digestion in the rumen, variable rates of neutral detergent fiber and the presence of mold and or mycotoxins.
Shelled corn hit by a killing frost before it reached physiological maturity – black layer at the point of the kernels – is likely to contain less than the normal 68 to 70 percent dry matter basis content of starch and a reduced feed energy value when harvested at more than 32 percent kernel moisture and stored as a high-moisture feed, the team of nutritionists indicates. A coarse roll rather than the usual more aggressive processing measures would probably be appropriate so the wet shelled corn doesn’t become too fine, they add.
The nutritionists cite a color code to noticing the types of mold that have already and or still could develop in the high moisture grain corn: whitish to pink star bursts on kernels throughout the ear to indicate fusarium, reddish rots starting at the tip of the ear for gibberella, a powdery green or blue green on or between kernels for penicillium and heavy or thick white masses of mold with kernels almost appearing to be glued to the husk as a symptom of diplodia, an ear rot.
Although they carry some of the same terminology, mycotoxins are not physically detectable, which is why the nutritionists recommend a test of any shelled grain corn which exhibited signs of ear molds. They note that plant wounding, temperatures above freezing, moisture above 20 percent and exposure to oxygen are all favorable to the development of mycotoxins and that the risk increases the longer the corn remains in the field.
In the fusarium family of mycotoxins, deoxynivalenol, commonly known as DON, is the most frequent and is far more threatening to livestock health and performance in grain corn than it is in corn silage, the nutritionists point out. The effect of the handful of mycotoxins in the penicillium family is not well known but the risk of having them can be reduced by proper harvest timing and ensiling methods, they note.
Nine mycotoxin testing laboratories in the Midwest, including Covance Laboratories in Madison, are listed in the advisory as facilities at which to test shelled corn for mycotoxins. Additional information is available in the Extension’s publication A3646, pest management in Wisconsin field crops.
