Growing Beef Newsletter
August 2026, Volume 17, Issue 2
Make 2026 your best corn silage season yet!
Gail Carpenter, ISU state dairy specialist
Corn silage is a forage that packs a punch with both starch and digestible fiber, and for that reason, it is foundational for cattle rations. Therefore, investing in the short window around and during corn silage harvest pays dividends when it comes to high quality feed throughout the year.
Set yourself up early
Even before harvest, late season plant health is essential for ensuring that corn silage quality stays high during the harvest window. Hot and humid conditions make a perfect environment for yeast growth and create ideal conditions for fungal diseases, including southern rust, which was identified in Iowa in late July. Unhealthy conditions result in corn that dries down rapidly in the field, resulting in a loss in quality and a narrower harvest window. Additionally, yeast contamination results in heating, which disproportionately burns up the starch portion of the plant. As a result, dry matter losses represent the most energetically expensive portion of the corn silage.
Timing is the most crucial decision for a successful corn silage season. In healthy corn, proper harvest timing can be estimated at the ¾ milk line. Some fiber digestibility may be lost from harvesting at a slightly higher dry matter, but the gains in energy from starch may outweigh these losses. However, in an unhealthy plant such as those contaminated with southern rust, drying hits the plant rapidly, meaning there is no flexibility to wait for a higher milk line. In contaminated or otherwise unhealthy plants, dry matter should be the main driver of harvest timing, and it should be considered that dry matter will change rapidly.
Pack it right
When it comes to silage harvest, packing is essential. Picture adding water to a jar full of golf balls. The water that fills the spaces represents the oxygen in the silage when it is not adequately packed. The presence of oxygen delays the start of fermentation and preservation, resulting in spoilage. Traditionally, two pack tractors per chopper are able to achieve the “800-lb rule,” a guideline that recommends 800 pounds of packing per ton of feed per hour. When choppers harvested at 100 tons per hour, this provided adequate packing. However, modern choppers can operate in the 250-280 tons per hour range, so producers must consider logistics of how to increase packing density. Another variable impacting the efficacy of the pack tractors is how efficiently drivers are using that weight. Consider watching how much time the tractor spends off the pile, for example, looping around and getting back on the pile. Ensuring that pack tractors spend as much time on the pile as possible will allow for the most efficient use of that weight.
Good packing is more than just equipment. While tractor weight does certainly have an impact on packing along with particle size and dry matter, the biggest management impact on packing density is layer thickness. Logistically, thin layers can be challenging, with harvest crews working to get silage into the bunk as quickly as possible. Ultimately, silage packing is a balancing act, and it looks different for every farm.
Seal the deal
Covering the bunk is the best way to protect your investment after harvest. Traditional black and white non-barrier films will prevent the exposure of your corn silage to the elements and prevent spoilage and shrinkage from wind, rain, and snow. These can be used alone or in combination with an oxygen barrier film, which will prevent oxygen from contacting the silage, thus promoting anaerobic fermentation. There are also two-in-one products available which provide the benefits of both products with the additional convenience of only needing to spread one cover.
Safety above all
Of course, the most important aspect of corn silage management, whether harvesting, storing, or feeding, is the safety of all personnel involved. During harvest, when speed and efficiency are crucial, sleep is rare, and several large pieces of equipment are actively in use, it can be easy to let safety slide. Before harvest even begins, meet with your whole crew to review safety practices and ensure everyone understands that safety is a value of your operation. Consider having everyone wear high-visibility vests when on the job, especially around large equipment. Additionally, make sure water and electrolytes are available for all workers and that everyone stays hydrated.
Key Takeaways for a Strong Silage Season
- Manage late-season plant health.
- Let plant condition drive your timing.
- Prioritize packing by ensuring enough weight and thin layers.
- Cover the bunk promptly to protect the investment you just made.
- Make safety a stated value before harvest starts, not an afterthought once equipment is rolling.
No fly control or tick control measure should be considered a “one and done” strategy. All measures have their place, depending on the goals and environment of each operation. Work closely with your veterinarian to develop a well-rounded strategy to control flies, ticks, and other parasites to keep your herd healthy and performing.
This monthly newsletter is free and provides timely information on topics that matter most to Iowa beef producers. You’re welcome to use information and articles from the newsletter - simply credit Iowa Beef Center.
