Corn Silage Dry Down – Dry Weather Hastens Moisture Loss

With the dry weather, a close eye should be kept on corn silage moisture and maturity so the proper harvest time can be achieved to produce quality silage.
Corn Silage Dry Down – Dry Weather Hastens Moisture Loss - Articles


R.L. Croissant,

As the summer comes to an end, farmers are beginning to gear up for corn silage harvest. With less than average rainfall encompassing most of the state this summer, rumors of early harvest have been circulating. With the increase in rainfall these past few weeks, however, some corn that was not pollinated properly and doing poorly has been slightly recovering.

Monitoring corn moisture during this time in the season is crucial, as the moisture at which silage is stored according to the storage structure is one of the key factors in properly ensiled forage. The appropriate moisture helps to ensure proper fermentation, which will aid in the guarantee of high quality and minimize losses due to seepage and mold.

Corn silage and grain samples collected by Alyssa Collins, Director of the Southeast Agricultural Research & Extension Center in Landisville and Assistant Professor at Penn State, show different relative maturity hybrids planted at different dates and the progress of dry down.

Relative Maturity
96 day, planted 4/21/16
103 day, planted 4/22/1670%35.3%
110 day, planted 5/26/1670%-

Waiting too long to harvest could result in too dry of silage for proper fermentation. With the quick dry down rates that are occurring currently due to weather, closely monitoring your corn is critical. 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 .