Fit silage to structure

Jul 26, 2013
by DTN

This year’s cool, wet spring and delayed plantings may lead to more farmers harvesting corn for silage this season.

Timing of harvest for corn intended for silage is vital to ensure the best quality. However, it is most crucial to time harvest for the correct moisture level for the type of silage structure you are using.

Farmers need to time corn harvest correctly to be able to preserve and ensile corn so that it goes through fermentation properly for the type of structure they intend to put it into, according to Joe Lauer, corn agronomist at the University of Wisconsin- Madison.

What dictates harvest timing the most is silage structure, he said. “Every structure has an optimum range.

You need to make sure the corn going into those silos is at the correct moisture so you can get proper fermentation, the silage can be preserved longer and will be better quality when it comes out.”

For a horizontal bunker, the structure most commonly used for corn silage, corn needs to be at about 65 percent to 70 percent moisture, he said. A lot of people use large silo bags, which requires between 60 percent to 70 percent moisture.

An upright concrete stave silo requires corn at between 60 percent and 65 percent moisture. Less common are oxygen-limiting fiberglass silos, which function best with corn between 50 percent and 60 percent moisture, he said.

Farmers can also check kernel stage to help with timing for correct moisture, specifically checking the milkline, Lauer said. If you break an ear of corn in half, you can see the milkline on the kernels. It is a visible borderline between the bright yellow outer portion of the seed that is hard and the duller yellow lower portion of the seed that is still milky and more fluid. For more information on milkline, visit:

There is usually about a 30-day period for the milkline to move from the crown to the tip of the kernel, Lauer said. “As soon as the milkline begins to move, as soon as you can see it, you need to go out and take moisture measurements.”

Once the milkline begins to move on the kernels, farmers will know the crop will begin to dry down, typically at a rate of about half a percent a day on average. Of course, if plants are wet, drying will take longer. Conversely, plants in drought areas will dry faster.

Lauer, however, stressed that while the milkline is used as a guide, it is still the moisture for the type of storage structure that dictates the timing of harvest. He gave two examples as farmers chop several plants representative of the field to test moisture and they see the milkline begin to move.

If plants are at 74 percent moisture, and figuring half a percent drying per day for corn intended for a bunker silo, a farmer could starting filling the silo at about 70 percent moisture, or about eight days on average from the time he took the sample.

To fill a concrete stave silo, starting at about 65 percent moisture, you would be looking at a total of 18 days until you harvest.

“It all hinges on the structure you’re trying to fill,” he said.

Getting the moisture level in corn correct for harvest is vital for silage, Lauer said. Corn that is harvested too wet will have seepage and will be sour—much less palatable for cattle. Corn that is harvested too dry is more susceptible to mold and spoilage, and the energy and protein digestibility of the silage declines.

With normal planting dates, corn is ready for harvest at about mid-September on average. However, since soil moisture currently varies between major corn-growing areas, it is difficult to predict the exact date for harvest.

“There’s quite a range that can occur. It all depends on the growing season,” he said. “It can be as early as late August, or as late as the first week or two in October.”

Whether corn is mature enough to harvest for grain or silage is one consideration for farmers, but what if a killing frost occurs before plants are even mature enough to cut as silage?

Lauer stressed that all silage harvest still depends upon putting it up at the right moisture for the type of storage structure you intend to use. Although the killing frost stops growth, the corn may still be too wet for the storage structure it is going into. This could take as much as seven to 10 days before the froststricken corn is ready to be chopped, he said.

“It’s not really a matter of development of the crop,” he said. “The farmer has to wait until the corn is the right moisture after a killing frost.” — Cheryl Anderson, DTN