Corn Silage Dry Down Update: Week of September 2

Penn State Extension educators continue monitoring corn silage dry down across Pennsylvania.

Corn silage harvest is in full swing in the southern portion of Pennsylvania, and where dry conditions persist in other regions, silage corn is continuing to draw closer to the optimum moisture content for harvest. If not monitored closely, the corn could go from ideal moisture to too dry, increasing the risk of storage losses. Silage harvested below the optimal moisture content can be difficult to pack and lead to a failure in excluding air to ensure proper fermentation, resulting in molding and heating of the forage, and in turn reducing quality.



According to the Penn State Agronomy Guide, corn silage should be harvested when whole plant moisture reaches 55 to 68%. For conventional upright silos, optimum moisture should be 63 to 68%; bunker silos – 65 to 68%; oxygen-limiting silos – 55 to 60%; and ag bags – 63 to 68% moisture.

Knowing the average expected dry down rate per day for corn silage is 0.5 to 0.6% will help to aid in determining proper harvest timing when moisture becomes close to optimal; however, the dry down rate varies by hybrid, and dry weather conditions further quickens the loss of moisture and could cause 0.7-0.9% dry down on a daily basis. Although not perfectly accurate, a quick field test for estimating corn moisture levels can be done by breaking an ear in half and looking closely at the bottom half of the tip of the kernels. When the separation, or “milk line”, is ¼ of the way down the kernel, moisture is approximately 70%. As the milk line reaches to approximately ½ of the way down the kernel, the moisture is approximately 65%. For a more accurate measurement of whole plant moisture, take a few plants at dent stage and run them through a chopper or lawn mower, allowing for all the plant parts to be thoroughly mixed together. Then use a Koster tester or a microwave to determine plant moisture by first weighing the wet sample, then slowly heating while continually stopping and stirring until the sample is completely dry. The difference in the weights of the wet and dry sample will indicate the moisture level of the silage. For more detailed instructions on using the microwave to determine moisture content, visit Determining Forage Moisture Content with a Microwave Oven .



In the case of chopping silage that has become drier than the optimal moisture according to your storage facility , there are some management recommendations that can aid in ensuring proper fermentation and quality of your forage.

  • Decreasing length of cut and creating a finer particle helps to promote better packing, as well as increases the digestibility of the kernel. However, when the particle size is smaller as a result of the finer chop, rations should be modified to ensure adequate digestive fiber.
  • Water can be uniformly added to dry silage to increase moisture content to aid in proper fermentation. When adding water to silage, the fill rate of most silos should be slowed as a result of slow water flow from most garden hoses and to ensure uniform water distribution.
  • Liquid inoculant additives can be used to promote aerobic stability, such as propionic acid and Lactobacillus buchneri, and decrease mold growth. These inoculants should be added at concentrations based on the manufacturer’s instructions.
  • Kernel processing helps silage to pack more densely which could lead to better stability of aerobic organisms, helping to aid in proper fermentation, as well as boosting the forage quality by increasing starch digestibility of the kernel, which could be a problem in dry silage.

To get an estimation of current field conditions around the state, extension educators around the state continue dry down sampling. This chart illustrates dry-down testing and growing degree day accumulations for this week’s sampling effort.



County Hybrid Planting Date Silking Date Sample Date GDD (after silking) Moisture
Blair Local 1837 April 8 July 3 August 30 1265 62%
Blair Local 1837 April 22 July 14 August 30 1017 66%
Blair Masters Choice MCT 5663 May 15 July 19 August 30 900 67%
Blair Masters Choice MCT 5375 May 24 July 25 August 30 759 71%
Bradford Pioneer 0921 May 21 July 31 Sept. 3 602 71%
Lancaster Pioneer 0843 May 23 ——- August 27 ——- 73%
Lancaster Pioneer 0843 May 24 ——- August 27 ——- 67%
Lancaster Dekalb (97 day) May 24 ——- August 27 ——- 48%
Lancaster Pioneer1197AM May 18 ——- August 27 ——- 69%
Lancaster Pioneer1316AM May 24 ——- August 27 ——- 69%

Where trade names appear, no discrimination is intended, and no endorsement by Penn State Extension is implied.

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