Whole-Plant Moisture — Knowing When to Pull the Trigger on Harvest

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Now is the time for final preparations for the corn silage harvest.

Years ago, experts recommended corn silage be harvested at the black-layer stage of maturity. In recent years, research and field experience have shown this practice usually results in silage that is too dry.

Positioning of the kernel milkline is another method of maturity staging that has been used as an indicator of when to harvest whole-plant corn for silage. The best lactation performance by dairy cows has been shown to occur at roughly the one-half milkline stage of maturity.

But recent research and field experience have shown considerable variation in the relationship between whole-plant moisture content and positioning of the kernel milkline. This variation is related to differences in hybrids and their dry-down characteristics and differences in growing conditions. Blindly harvesting whole-plant corn for silage at the one-half milkline sometimes will result in silage without the right moisture content for good preservation and utilization.

The best use of kernel milkline positioning is as an indicator of when to start monitoring whole-plant moisture content. Once most of the kernels are dented and the milkline is visible, this is the time to chop some whole plants for measurement of moisture content. Whole-plant moisture content should be your trigger for when to harvest corn silage.

You must pay special attention to making an accurate determination of moisture content. Most years, corn takes 55 to 60 days to go from three-fourths silking to the black layer. The chopping time for corn silage is about 10 to 15 days before the corn reaches the black layer. Be sure to check the whole-plant moisture to fine-tune timing.

Another useful tool is the U2U Decision Support Tools. The Corn Growing Degree Day (GDD) decision support tool puts current conditions into a 30-year historical perspective and offers trend projections (based on climatology) through the end of the calendar year. You can find it at https://mygeohub.org/groups/u2u/gdd.

Your ideal silage moisture depends on the storage structures you have.

The cutter bar setting is another important element in making high-quality corn silage. If you are using a kernel processor (all kernels are crushed), then set the theoretical length of cut at 3/4 inch and the processor silage roller at 1 to 2 millimeters. For unprocessed corn silage, set the theoretical length of cut at 1/4 inch, but make sure some pieces of stalk are about 1/2- to 3/4-inch long to help maintain effective fiber in the ration. The dryer the silage, the higher the value of the kernel processing.

Packing silage, especially in bags, bunkers and piles, also is very important. With bags, set the tension as tight as possible. The goal is 14 pounds of dry matter or more per square foot of silage. Bunkers and piles should be filled using the wedge method, which is filling at a 40-degree angle. Com silage should be spread into layers no thicker than 6 to 8 inches and then packed completely before the next load is delivered.

Tower silage will pack because of the head pressure created, but it will pack much more uniformly if you have distribution through the silage delivery spout that will layer the silage rather than form a pile.

Finally, all bunkers and piles should be covered with plastic within 12 hours of finishing chopping. Remember that deterioration penetrates well beyond the color difference at the top.

With no cover, Kansas State University researchers measured 80% dry-matter loss in the top 10 inches. Covering with plastic reduced dry-matter losses to 20% in the top 12 inches. Don’t waste that amount of forage or sacrifice its quality.

Harvesting whole-plant corn at the right moisture content and particle size is crucial to making high-quality corn silage that is well utilized by cows. Whole-plant moisture content rather than kernel milkline positioning should be your trigger for when to harvest corn silage. If you use additives, apply them properly, pack thoroughly and cover securely to minimize storage losses.


You can find the full article here.

Originally published on Sept. 15, 2014

J.W. Schroeder, North Dakota State University Extension

Sponsored by Lallemand Animal Nutrition


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