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Published August 28, 2009, 02:55 PM

Early harvest, immature corn still valuable

Due to late planting dates and a cooler than normal growing season this year, many corn fields may be harvested for silage. There is even great potential for corn in these fields to be too immature for proper corn silage harvest.

By: Jim Stordahl, Clearwater/Polk Extension

Due to late planting dates and a cooler than normal growing season this year, many corn fields may be harvested for silage. There is even great potential for corn in these fields to be too immature for proper corn silage harvest.

The questions arises of how should the value of corn silage be adjusted for frosted or immature corn. The usual calculation methods for pricing normal corn silage include:

1) Relative feed value of a known forage market.

n Silage ($/T) = ¼ to ½ value of hay

n Silage ($/T) = 6 to 8 times the price of a bushel of corn. If it’s already harvested, then 10 times.

2) Feed replacement or substitution costs.

3) Market prices for energy, protein, and digestibility (NEL of corn, soybean meal, hay).

4) Contracted price above the cost of production (which now tops $400/acre).

For most crops, forage quality and value decreases with maturity, that is fiber levels increase and digestible energy decreases. Corn is somewhat unique in that quality increases with maturity. In corn silage, most of the digestible energy is in the grain portion. Immature corn will have a lower proportion of grain in the silage. Two approaches to consider for calculating the value of immature corn silage are:

n Reduce the value of immature corn silage by the cost of buying back grain to bring the grain:stover ratio to a more normal proportion.

n Use University of Minnesota Extension software to calculate the milk per acre and milk per ton that could potentially be produced from immature corn silage.

Frost before physiological maturity will significantly reduce grain yield. For example, a killing frost at the soft dough stage of development would result in a grain yield loss of 55% and at least that much grain would be required to produce normal silage.

The relationship between kernel maturity and silage yield and quality is shown in the table below. Milk production per acre is 35 percent less when corn is harvested at the immature soft dough stage compared to the optimum stage at 50 percent kernel milk.

Milk production per ton of immature corn silage (soft dough) was 25 percent lower than the optimum stage of 50 percent kernel milk. Thus, the milk production potential would be reduced between 25 and 35 percent with immature corn harvested for silage. The value of the corn silage should be adjusted accordingly.

Lastly, don’t forget the crop insurance implications. Any insured field originally destined for the grain bin and will now become silage must be inspected and released by your insurance company. So, if you are contemplating the silage option, contact your crop insurance agent well before you plan to harvest the field.

For more information, contact me in McIntosh on Monday and Thursday, Red Lake Falls on Tuesday, or Bagley on Wednesdays.  Our toll free number is 800-450-2465. If e-mail is your thing, contact me at stordahl@umn.edu.

Source: Joe Lauer, University of Wisconsin Extension corn agronomist.

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