Milk Line & Corn Silage Moisture

How do you determine your corn silage moisture and learn about corn milk line.


First off, what is the milk line?

See images above from Hay & Forage Grower and Trellis

Is milk line a good way to determine corn silage harvest?

When preparing for corn silage harvest, looking to the milk line may not provide the answer on when to harvest.

Moisture is the key to a good fermentation from your harvest, this is the whole plant moisture not just the moisture levels in the kernel. Throw in a wrench of 2020 when some corn isn’t even showing a milk line due to plant stress and relying on milk line is unreliable.

When looking to harvest corn silage, the wetter the better.With wetter corn silage, processing is less critical and the weight from the water creates self–packing, preserving the moisture in the cells of the plant.The wetter the forage at harvest, the better the preservation.  Harvest for plant moisture in the low 70s for drive over piles, bags, and bunkers. Plant moisture less than 70% may be needed for upright silo storage.

How can I determine corn silage moisture?

One can determine their moisture level with a silage sample using the following method with a microwave, as the microwave will eliminate water molecules and dry the sample down – Note that cooking the sample will cause an odor.


Microwave dry down method:

You will need a corn silage sample, gram scale, paper plate or bowl, glass of water, and microwave oven.

·  Collect silage sample.

·  Place glass of water in the back corner of microwave.

·  Dry paper plate or bowl in oven on high power for 1 – 1.5 minutes. Weigh the dry plate.

·  Weigh 100g of silage into the dry plate/bowl. Record this as the Original Wet Weight.Spread the sample evenly on a paper plate for even drying

·   Start drying process at 50% power for 4 minutes. Weigh sample.*

This step may need to be repeated several times in order to complete they drying process. Reduce microwave drying time as the sample dries. Note that any char on the sample means the power was too high and/or dried too long, and a new sample should be done.              

·   Check weight of the sample until weight change is less than 2 grams.

·   Record this final weight as the Dry Sample Weight.

Once the sample has less than a 2 gram change with this drying method, calculated the percent dry matter:

Dry Sample Weight/Original Wet Weight x 100% = % Dry Matter
100% - % Dry Matter = % Plant Moisture

Dry down in the fall happens very quickly – In fact the average dry-down rate is 0.5% per day – That means the average corn plants islosing .5% moisture each day.

Stay aware of condition changes to ensure harvest of a quality feed for your herd.

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