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Corn Silage Dry Down - Fast Dry Down Rates Observed

Report from Lebanon County on dry down of corn silage crop.

Corn silage is one of the most reliable forages grown as a main source of feedstuff for cattle. Growers have invested a tremendous amount of time and money to plant and maintain fields to get them to this point of harvest and ensiling. The moisture matched to the structure in which it will be stored is absolutely critical to proper fermentation as is the quick and proper packing and subsequent feed out rates all come together to maintain high milk yields in the end. Too wet and seepage and improper fermentation may result, too dry and pockets will develop trapping oxygen in the pockets and allowing molds to develop. Here are some review items to consider.

Dry down is really variable among hybrids but in general this year the dry down is hastened and some growers are reporting silage is drying down sooner than expected given the weather. John Bray, Extension Program Assistant, has been gathering samples for the last two weeks to monitor dry down. Yesterday we chopped more corn silage to get an idea of silage dry down. For corn planted 4/28 a 96-day hybrid tested 64.5% moisture on 8/29 and yesterday on 9/8 is 51% losing 1.3 points per day. Another 106-day hybrid planted on 9/8 that tested 69.5% on 8/29, yesterday 9/8 tested 60.5% losing .9 points per day. A 112-day hybrid planted on 5/13 tested 68% on 8/29 today is 65% moisture losing .3 points per day.

There is variability between hybrids, the average is .83 point per day.In a typical year we would expect about a .6 point per day drop so this season is drying a bit quicker than normal. The point here is to gather moisture samples and get an accurate measure of the moisture to assist in proper timing of harvest. In communicating with a custom operator, they related that they are finding corn is drying down fast. “Guys need to keep on top of it. I did some yesterday. Friday corn was 69% and on Monday, corn was 67%, about a percent a day. It was 105 day corn. For a Ag bag 66 percent is about great".

Moisture Testing

There are numerous methods to determine the moisture of the forages. We utilized a Koster Tester (@$300.00) to obtain our results and chopped the corn using a modified home shredder. Many farms keep a Koster in or near the feed room and makes it ideal to keep track of changing forage moistures. A microwave oven and a small scale can also be used for this purpose. The point is that growers need to arrange for a quick and easy method to measure moisture.

What if my forage is dryer than the structure available?

Dry corn silage can lead to numerous feed out issues due to improper fermentation and in extreme cases cause fires in silos. Adding water to dry silage is widely used however may prove impractical because of the amount of water and the fact that this water is extra cellular not intercellular and may not prove useful. For example it would take almost 150 gallons of water to go from a 45% dry matter to a 35% (Undersander 9/9/2014). Locally however many growers will use water to aid in packing the top third of silo structures. Dry silage also will have harder kernals and the starch components will change and kernal processing becomes more useful in chopping dryer corn silage. Inoculation of dry silage may prove useful as the dryer conditions may result in less naturally occurring bacteria. One solution in extreme cases where a trench or bunker was the targeted structure is to go with an oxygen limiting structure for the dryer silage such as a bag to avoid the pitfalls and ensure better fermentation and harvest other ideal moisture silage for the bunker if possible.


Be safe. It is that time of year that growers are at a high risk of injury. Aside from the road hazards and physical stress, with silos the gas can be deadly. Observance of the 2-3 weeks of time it takes to allow for the gas to escape is advisable. Do not enter the silo until the blower has run for at least 20 minutes to remove the gases. Any yellowish brown fumes or bleach like odors should be a clue to keep humans and animals away until it is safe to enter.

There will be numerous other issues pertaining to this year as many fields were late planted and silage harvest will be pushed to the season end. In discussing this with a grower yesterday, he has corn that is just silking now and will require 40-45 days to black layer so for silage harvest it might mean another 30 days to get this later planted corn to silage.

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