How Do I Know When it’s Time to Harvest my Corn for Silage?

Timing is key when harvesting quality corn silage. Here’s how to make sure you’re hitting that window of opportunity.

Proper harvest timing is key when it comes to storing high quality corn silage. Optimum moisture content at harvest is essential in the promotion of fermentation, which results in high quality silage. While the optimum level of moisture may vary depending on the type of ensiling system you plan to use, a moisture level of 65% is a good estimate. At this moisture content, the silage can be adequately compressed, and the oxygen is removed more quickly. The quick transition to an anaerobic environment promotes the development of lactobacillus bacteria (the good guys). At a lower moisture content, oxygen is not quickly excluded, and mold can continue to grow and heat the silage. At a higher moisture content, clostridia bacteria begin to grow, and create silage that smells rancid — resulting in lower palatability and quality.

So how do you determine when the corn is at the proper moisture content for silage harvest? Many growers rely on the maturity of the corn, and plan to harvest shortly after the corn reaches the dent stage. While this is generally a safe estimate, the moisture content at dent stage can vary widely based on corn hybrid and weather patterns. A more accurate measure of moisture content comes from analyzing whole plant samples.

 

Now, I realize that most people don’t have personal access to a moisture tester or forage quality lab. However, good estimations of moisture content can be obtained with the use of a scale and a microwave. Take several whole plant samples from your field- enough to be representative of the average field condition. Break samples down small enough so that they will fit in your microwave. Measure the weight of each sample prior to heating it in the microwave. Heat the sample in the microwave on high for about 5 minutes and weigh the sample again. Return the sample to the microwave for another minute. Weigh the sample again. Continue this process until two consecutive weight measurements are the same. This measure is the dry matter content in your sample. Subtract the dry matter weight from the original weight to obtain the weight of water in your sample. Divide that amount by the original weight of the sample to determine the moisture content.

 

Now that you have a moisture content, you can make management decisions about your crop. Is the crop too dry and better suited for grain corn? Is it time to get equipment moving and get ready to begin chopping or call your harvester if using a custom operator? Or, should the crop be left for a few more days and have the moisture retested? Knowing the condition of your crop is the first step in being able to make informed management decisions.