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When is the Time Right to Harvest Corn Silage?

Taylor Leach

July 27, 2020

As the sun-filled days of summer slowly slip into the crisp, cool days of fall, a late summer breeze brings in the sound of rustling corn stalks that are nearly ready to be harvested for silage. With it comes a feeling of anxiety for producers who are wondering, “Is it time to harvest?”

If this thought is racing through your mind as well, here are a few things to consider before you drive the chopper out of the shop.

“Proper harvest timing is key when it comes to storing high quality corn silage,” says Casey Guindon, an educator in field and forage crops at Penn State University.

“Optimum moisture content at harvest is essential in the promotion of fermentation, which results in high quality silage. Knowing the condition of your crop is the first step in being able to make informed management decisions.”

Guindon recommends harvesting at a moisture level of 65%, or 35% dry matter, depending on the type of ensiling system you plan to use. 

“At this moisture content, the silage can be adequately compressed, and the oxygen is removed more quickly,” she says. “The quick transition to an anaerobic environment promotes the development of lactobacillus bacteria. At a lower moisture content, oxygen is not quickly excluded, and mold can continue to grow and heat the silage. At a higher moisture content, clostridia bacteria begin to grow, and create silage that smells rancid -- resulting in lower palatability and quality.”

Another way to estimate the timing at which the corn is right is to calculate the number of days after pollination, according to Emily Carolan, a territory manager for Pioneer Seeds. This can helpful in providing an idea as to when to run plant moisture samples.

“Once [the corn] hits half milkline, we know whole plant moisture will start to drop, so chopping should be close by,” Carolan says.

When the moisture content is right, start harvesting earlier rather than later, recommends Donna Amaral-Phillips, an extension professor at the University of Kentucky. 

“Harvest over as short a time frame as possible,” she says. “Quality and consumption drops off after [you reach] 40% dry matter.”

Once the decision has been made to harvest, there are several factors to consider when it comes to storage.

For silage piles and bunkers, the silage should be spread in 4 in. thick layers in a wedge configuration at a speed of 1.5-2.5 mph., according to Amaral-Phillips. Make sure to not turn around on the silage surface as this can loosen the packing density. Packing is complete when the surface is covered with tire tracks and is smooth.

For silage bags, make sure that the bagger is working properly and that there are no holes or tears in the plastic. If possible, try to set the bags on a concrete or asphalt surface to minimize mud at feedout, Amaral-Phillips recommends. Mud decreases feed quality and increases possibility of unwelcome bacterial contamination of feed.



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