Ray Mueller
Correspondent
MADISON
Trying to salvage the best use and value from the remaining non-harvested portion of their 2009 crop is uppermost on the minds of many corn growers as October moves into November.
University of Wisconsin Extension Service agronomists addressed that concern this week with the release of advisories on the harvesting and storage considerations of this year’s very high moisture grain corn and on understanding the corn test weights. Additional advisories are scheduled in the coming days on field drydown rates, the effect of corn quality on feeding livestock, the proper settings of combines for harvesting very high-moisture corn, harvesting corn as earlage or snaplage, the storage of low-quality grain, the costs associated with drying and otherwise protecting such grain in storage and setting priorities for completion of field work before winter sets in, according to Extension Service corn agronomist Joe Lauer.
Fond du Lac County crops and soils agent Mike Rankin prepared the two advisories circulated this week. He suggested that the pertinent question being posed by corn growers when deciding how and when to harvest and then store the high-moisture grain corn that’s still on their fields is “What can I get away with?”
When “even the best plans to ensile high-moisture corn at the proper moisture level are sometimes thwarted by weather and time constraints,” growers need to recognize the special factors pertaining to their crop, Rankin indicates. “The maximum moisture percentage to preserve corn becomes a primary issue when crop maturity has lagged behind normal or frost puts an early halt to the growing season.”
Be especially wary of trying to store grain corn with more than 40 percentage moisture in any kind of facility, Rankin warns. “Undesirable fermentation may take place and yeast may proliferate along with ethanol levels. Animal acceptance may be poor with this type of fermentation.”
For conventional top unloading silos, bunkers and silo bags, the ideal kernel moisture is 28 percent to 32 percent for shelled corn and 32 percent to 36 percent for ear corn, Rankin points out. The respective upper limits are 36 percent and 40 percent while the minimum percentage is 26, unlikely to be relevant very often this year, he adds.
The recommended kernel moisture is lower for bottom unloading oxygen-limiting silos, Rankin continues. For shelled corn, the maximum is 32 percent, ideal is 26 percent to 28 percent and the minimum is 24 percent. With rolled ear corn, the respective percentages rise to 36, 28 to 32, and 26.
While most high-moisture corn is processed – rolled or ground – before being placed in storage, Rankin lists two exceptions. They are corn with 35 percent or higher kernel moisture and shelled corn put into an oxygen-limiting unit.
Increase the degree of processing as corn approaches the optimum moisture content but go easy on that with very high moisture, Rankin states. “Excessively fine high-moisture corn may result in rumen acidosis, butterfat test depression, off-feed problems or an increased incidence of displaced abomasums.”
For devising a harvesting strategy and timetable, Rankin suggests harvesting the lowest moisture corn first and placing it at the bottom of storage units. This will enable feeding of the highest risk corn during the coldest months of the year, thereby reducing the odds of heating and spoilage while in storage, he explains.
The risk of mycotoxin development can be reduced by harvesting corn with the highest moisture kernels as shelled corn rather than as snaplage or ear corn, Rankin says. The same applies for corn which already has significant mold on the kernels or cobs at harvest, he adds.
Place silo bags holding high-moisture corn away from trees and tall grasses and regularly remove any snow from around them, Rankin asks growers. Remove the corn from them first in order to avoid the risk of rapid and extensive spoilage that can easily occur around punctures, rips and tears during the summer, he notes.
Moldy corn is a problem that corn growers across the Midwest are battling this fall, Purdue University agronomist Richard Stroshine noted in a recent commentary. “If farmers try to operate like they normally do during harvest this year, it could cause some major problems during the storage of this year’s crop,” he warned.
Stroshine cited a grain elevator operator who indicated that the amount of the mold is the highest since 1974 and a grower who found that 15 percent of the kernels in his harvested corn had been damaged by mold. One point that Stroshine emphasized is to remove as much of the fine material and broken pieces of corn as possible and striving to dry the corn that’s intended for sale as number two dry corn to 14-14.5 percent moisture.
“Use the combine’s full capabilities to get rid of the fine material and incorporate high-capacity screen cleaners into the grain handling systems,” Stroshine stated. Even though it is appealing to get corn off the field in order to limit the mold growth, he also warned that not getting wet corn into a dryer immediately after harvest will probably reduce its shelf life and make it more susceptible to additional mold when encountering any later stresses.
To the notion of blending moldy corn with good corn, Stroshine said, “my recommendation would be to segregate the good corn from the bad. If need be, it could be blended later.”
When dealing with high-moisture corn for which drying is not an option, boost the odds of protecting its quality while in storage by applying propionic acid or another acid mix including propionic, Rankin advises. “The propionic acid will not lessen any problems from the mold but will likely prevent mold problems from becoming worse.”
Preserving high-moisture grain corn in storage is more difficult than with corn silage because the rate of fermentation is slower, the high levels of starch promote aerobic deterioration and the extended presence of oxygen nurtures yeast growth, Rankin explains.
While he considers one or more of the acid products to be the top choice as a preservative because of their proven effectiveness, Rankin also acknowledges that they cost more than the standard inoculants and require specialized equipment for the application. He says “it’s a must” to apply propionic acid to any high-moisture corn stored on floors or in bins of concrete or wood.
The proper application of propionic acid reduces the pH of the stored corn to about 4.0, thereby inhibiting the growth of harmful micro-organisms, Rankin indicates. “The cost of treatment is usually comparable to that of on-farm drying.”
What the proper application rate is depends on the grain’s moisture content and the intended length of storage, Rankin points out. With kernel moisture near 30 percent, he says it typically takes 10 to 20 pounds of actual acid to properly preserve one ton of high-moisture corn.
For 6 months storage, Rankin indicates 3.3 to 5 pounds of actual propionic acid per 1,000 pounds of corn at 20 percent moisture and gradually increasing the amount to 8.5 to 10.5 pounds at 35 to 40 percent moisture. At those percentages, the propionic acid rates would increase to 4 to 6 pounds and 11 to 14 pounds for 9 months of storage and to 5 to 7.5 and 12.5 to 15 pounds for 12 months of storage.
Rankin also mentions the possible scenario of filling an upright silo from which the corn will not be fed until much later. In that case, he suggests applying acid only to the corn in the top 5 to 10 feet of the silo because that is the area in which oxygen is most likely to infiltrate.
Removal rates also have to be considered, Rankin continues. He recommends a minimum daily removal of 3 to 4 inches during warm weather to prevent a new cycle of heating but also notes that this removal rate is not appropriate if the corn quality is detrimental to animal health. In such a case, treat the bottom third or half of the silo with propionic acid at 12 to 15 pounds per ton or with lactobacillus buchneri inoculant, he says.
Rankin likes L. buchneri as the top choice among inoculants as a high-moisture corn preservative because an extensive body of research has shown that it is very effective in all storage units. He says the L. buchneri’s role in boosting the production of acetic acid not only deters the growth of certain yeasts but also improves aerobic stability by limiting the temperature rise of the corn at feedout regardless of the ambient temperature.
Standard bacterial inoculants are also a possibility but only those specifically developed for ensiling high-moisture grain corn should be chosen and then applied at the manufacturer’s recommended rate, Rankin cautions. He notes that these inoculants quicken fermentation by producing extra lactic acid but some of them reduce the aerobic stability at feedout.
In a separate advisory issued this week, Rankin addresses corn test weight – a topic likely to be discussed widely by growers this year because of the immature crop which has resulted in a high volume of high-moisture corn. He points out that the simple way to understand test weight is that the test weight increases as the kernel moisture decreases.
That’s because an official bushel of corn measures 1.244 cubic feet, Rankin explains. This relates to test weight because more kernels fit into that volume when they shrink as they dry, he notes. Other factors which play a minor role in determining test weight are hybrid differences and physical traits of the kernels– size, density, shape and outer kernel layer slickness, he adds.
Rankin suggests that some confusion might exist about test weights because the official allowable minimums in the U.S. are 56 pounds per bushel for number one yellow corn and 54 pounds for number two corn. Because the weight is so contingent on moisture content, he points out that commercial grain buyers base their pricing on a standard moisture content of 15 percent or 15.5 percent.
To illustrate how test weight varies according to moisture content, Rankin cites a table which calculates the numbers for lowering the moisture to 15 percent from previous levels of 18 percent to 28 percent. For every two percentage points of reduction in moisture, the test weight increases by 0.5 pound. Starting at 18 percent moisture, drying the corn to 15 percent moisture adds 1.5 pounds to the test per bushel test weight while a reduction from 28 percent to 15 percent adds 4 pounds to the test weight.
