Testing Silage Moisture

With any ensiled feed, proper moisture at harvest is essential to getting a good pack and fermentation. Keep this in mind when harvesting corn silage this year to make sure your harvest produces a high quality product.

Silage should be harvested at 60-70% moisture. Higher moisture contents will result in improper fermentation and spoilage.  Too dry and we get a poor pack, heat, and more spoilage. Figuring out exactly where this sweet spot is can be difficult, but there are several methods we can use to figure out where we stand.

One of the easiest ways to check moisture content is the squeeze test.  Start by chopping a small test area.  Grab a handful of fresh chopped silage and squeeze it in your hand as tight as you can for about 30 seconds.  If juice drips from the sample, it is too wet for a good ensile and proper fermentation.

 If no juice drips out, open your hand slowly.  If the ball falls apart quickly and your hand is barely wet, the forage is too dry.  A ball that holds together and leaves the hand damp means moisture content is just about right. 

While the squeeze method is a good in field test, to pinpoint moisture content, we need to step up our game a bit. 

To start, we need a sample to test. When taking a sample for moisture testing, we can either test chop a few areas in the field and take grab samples from that or select 10-20 plants to chop by hand.  The key is to get samples that are fairly representative of the field as a whole.  We don’t want overly dry plants from a hill top or green ones from a drainage if the rest of the field is somewhere in between.  We also want to make sure that these test samples are chopped fairly fine to speed along the drying process.  This isn’t what we are going to be packing into a bunker, we want it to dry out quickly for testing.

Next we need to choose a method to dry out our sample with. If you are near Hartington, we can do a quick moisture content in our office with a Koster tester.  Samples are run on a first come/first serve basis, so call (402-254-6821) before you head our way to ensure we have an opening.  Drop your sample off and we can call you with the moisture level in 30-45 minutes of processing.

If you want to run the sample at home, we can use some common appliances like a kitchen dehydrator, or a microwave oven. 

For at home testing, weigh out around 100 g worth of sample on a scale for our starting green weight.  Be sure to tare out the container weight and select a container that can safely be put in the microwave if going that route.

Next we have to dry the sample down.  If using a microwave, put around 8 ounces of water in a glass in the corner of the microwave to help evenly dry things out and prevent burning. Next, put your weighed 100 g of sample in a microwave safe container and using the medium to high setting microwave for 3-4 minutes.  When time’s up, weigh the sample and record it. Stir and start microwaving in 30 second intervals or less if you think the sample is getting close to dry.  You don’t want the sample to burn.  After each microwaving, weigh the sample again.  When you have two weights that are the same or within one tenth of a gram of each other, the sample is dry. 

If using a dehydrator, spread the sample out and let it go over night.  Just like the microwave, after the initial dry down, begin weighing the sample at regular intervals.  When there is no change between the current weight and the one previously, the sample is dry.

Using this dry weight and the initial wet weight, calculate percent moisture by subtracting the wet weight from dry weight dividing by the wet weight and multiplying by 100.  Make sure your calculations and weights do not include the weight of your container, just the sample.

Pinpointing the exact moisture content of corn for silage is a key component in ensuring a good harvest and proper storage into the winter and is an easy process you can do at home.  If you want more information on silage harvest and how to fit it into your ration, contact your local extension office.

-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce.  He is based out of the Cedar County Extension office in Hartington.  You can reach him by phone: (402) 254-6821 or email: ben.beckman@unl.edu