Corn Silage Harvest 2019


Corn harvest for silage has started in Southern Wisconsin and will be starting soon in Central Wisconsin. Excessive rainfall this spring resulted in a lot of late planted corn which will present challenges for farmers in determining when to harvest that corn for silage.

Corn has two peaks in forage quality: one at pollination and one at 50 percent kernel milkline. Forage quality as measured by milk per ton is high during vegetative phases prior to flowering. Like all forages, quality decreases after flowering. Unlike other forages, quality improves as grain fill occurs. The early peak in forage quality at pollination is high in quality but too wet for ensiling. The later peak is more familiar and is the one we typically manage for when producing corn silage because it maximizes both biomass yield and quality.

If pollination is un-successful, the forage quality following the first peak does not change and will continue to remain high due to higher sugar content (water soluble carbohydrates), higher crude protein, higher crude fiber and more digestible fiber than normal corn silage. Unsuccessful pollination generally reduces yield and grain content resulting in increased fiber content, but this is often accompanied by lower lignin production that increases fiber digestibility. If pollination is poor yet some kernels are developing, the plant can gain dry matter and farmers should wait with harvest.

The harvesting challenge is that green, barren stalks will contain 75-90 percent water. Barren corn is difficult to harvest because it is too wet for silage storage structures. Arlington UW-ARS staff have had some success using a discbine to cut barren corn into a windrow. The windrow would need to dry to desiccate the forage. A forage chopper with a hay pickup attachment is then used to chop the windrow for ensiling. Grazing is an option, but there is a potential for nitrate toxicity. This is especially likely to be a problem if growth was reduced to less than 50 percent of normal and/or high levels of nitrogen were applied.

If the decision is made to harvest the crop for silage, the main consideration will be proper moisture for storage and fermentation. The crop will look drier than it really is, so moisture testing will be critical. Be sure to test whole-plant moisture of chopped corn to assure yourself that acceptable fermentation will occur.

A typical response of corn to stress is to reduce grain yield. Barren plants reduced whole-plant yield by 19 percent. With the exception of protein, as ear fill increased, whole-plant forage quality increased.

Research experiments were conducted during 2005 and 2006 to determine what could be expected by planting corn in July. Three corn hybrids (brown midrib, full-, and shorter-season) were planted on five different dates from April 28 to Aug. 1 at Arlington. The 2005 growing season had a killing frost on Oct. 26, which was three weeks later than normal.

Seasonal dry matter production after planting during July ranged from 7.5 to .7 Tons Dry Matter (DM)/A while the same hybrids planted April 28 to June 1 produced 10 to 8.7 T DM/A. Milk per acre is significantly was reduced 92 to 17 percent to levels ranging from 24,000 to 2,300 lbs milk/A for planting dates in July. Crude protein, NDF, and NDFD increased with later planting dates.

Although, little starch content was measured in later planting dates, overall milk per ton tended to decrease slightly. Thus, relatively small changes in milk per ton occurred during planting dates in July with levels ranging from 2800 to 3200 lbs milk/T, which was a 5 to 8 percent decrease from corn planted April 28 to June 1.


Corn can produce significant dry matter yield when planted during July, but the amount produced depends upon when a killing frost occurs.