High Quality Corn Silage Means Correct Timing

Corn silage should be of good to excellent quality in North Dakota this year, according to Duane R. Berglund, extension agronomist at North Dakota State University. The 2001 corn growing season has resulted in well developed silage corn grain with potential for high quality and energy content.

Many producers wonder when is the best time to chop corn, before or after a hard killing frost, at what moisture content and how to prevent excessive seepage losses.

"Corn makes the best quality silage when the grain portion is near physiological maturity," Berglund says. "When chopped at this corn development stage, silage will have about 50 percent corn grain and cob by weight."

The corn grain and cob portion contains about 60 to 65 percent of the nutritive value of high quality corn silage. At physiological maturity the corn has attained its maximum dry matter weight per acre, maximum forage digestibility and maximum total digestible energy per acre.

The moisture content of the chopped corn crop (stalks, leaves and ears) should be about 63 to 68 percent for ideal silage fermentation. Under most favorable conditions the corn should be harvested at the hard dent or glazed kernel stage with green stalks and leaves.

The best method to determine if corn is ready to chop for silage is to observe the "milk line" on kernels, says Berglund. On sampled ears from five or six field locations, break the ear in two and examine the kernels opposite the germ side. The "milk line" is the cream-colored dividing line between the starchy part of the kernel and the milky dough below. The milk line will move from the top of the kernel toward the tip as corn grain matures. The best silage is when the milk line is one-half to one-third or less.

Various storage methods can safely store corn silage at different moisture levels; for bunker silos or AgBags, a whole plant moisture of 68-72 percent; for upright stave silos, a moisture of 63-68 percent, and for oxygen limiting silos 50-60 percent.

How fine to chop silage is a question producers often ask. "The drier the silage, the shorter the cut you should make," according to Berglund. " Don’t try to chop the silage fine enough to break up all the kernels — this doesn’t make the forage any better for the cows, and might even cause a drop in milk fat when fed to dairy cows."

If a hard freeze gets to your corn before chopping, producers may need to change harvesting strategy to get the most nutrient value out of the crop.

If the corn is already mature (near 65 percent moisture) when frost hits, get it into the silo as soon as possible to minimize field losses. If it is still green, leave frost-killed corn on the field until it dries to 62 to 68 percent moisture. "Frost speeds the drying process, so you’ll have to keep a close eye on the corn to make sure you bring it in before it gets too dry," says Berglund.

If corn borer damage is causing considerable ear drop, Berglund recommends harvesting the corn for silage on the early side to prevent loss of nutrients contributed by the ears.

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Source: Duane Berglund, (701) 231-8135, dberglun@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, Richard_Mattern@ndsu.nodak.edu

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