Water Content Key in Making Corn Silage

Whole-plant moisture and the plant’s maturity at harvest affect corn silage quality, according to Kevin Sedivec, North Dakota State University Extension rangeland management specialist.

“Making corn silage requires moisture for proper fermentation to minimize dry-matter loss and spoilage,” he says. “Ensiling at the correct whole-plant moisture content and optimum plant maturity is critical.”

Corn should be harvested for silage at a moisture content of 65 to 70 percent when using a horizontal bunker. If too wet – above 70 percent – yield potential is reduced and seepage will occur, resulting in the undesirable presence of clostridia bacteria fermentation.

Clostridia bacteria are very inefficient, converting forage sugars and organic acids into butyric acid, carbon dioxide and ammonia. Silage with these bacteria loses dry matter, creates a foul smell due to the butyric acid, and has a higher pH, and poor forage quality and palatability.

Seepage results in a loss of nutrients that can be harmful to the environment and can allow feed to freeze during the winter.

Making silage when the corn is too dry results in poor packing, inadequate air exclusion, poor fermentation and heating. Dry silage creates higher levels of spoilage and low bunk life.

Visually Estimating Water Content
So, approximately how much water is in your standing corn? This year was classified as an earlier maturing year for corn, which was drying faster than normal due to dry conditions in late July and August.

Researchers tested standing corn, including the cob, for moisture content Aug. 15 at the NDSU Central Grasslands Research Extension Center near Streeter, N.D. Here is what they found:

• Corn with the entire plant still green, tasseled and having two cobs in the R2 kernel stage (early kernel, no denting and no milk) was at 77.4 percent water content.
• Drought-stressed corn with the bottom three to four leaves that were brown tested at 76.5 percent water content. The plants had one cob in the R2 kernel stage.
• Drought-stressed corn with the bottom four to seven leaves that had turned brown and no cobs had a water content of 67.9 percent.

“Based on these findings, drought-stressed corn with the bottom four to seven leaves brown and dry was at the proper moisture content for silage fermentation,” Sedivec says. “This silage would have no cobs and would be lower in production and energy content.

“Drought-stressed corn that was dry throughout and contained no cobs had water content less than 60 percent,” he notes. “This corn silage would be considered too dry and produce lower-quality silage.”

He advises that when corn is not stressed by drought, producers should make silage when the corn is at the dent kernel and approximately 75 percent milk stage.

Testing Moisture Content of the Field
“What is important to note is that these results were based on standing corn in south-central North Dakota, and the moisture content can vary in your field based on the level of drought and the corn hybrid,” Sedivec says. “With many new corn varieties selected for the ‘stay-green’ trait, visual estimates can be quite variable, based on environment and management.”

He recommends producers start testing their corn fields for water content once the kernel reaches the dent stage and drought stress is not present. Once they have determined the percent of moisture, they need to be aware that whole-plant moisture has an average dry-down rate of 0.5 percent per day.

“Dry-down will speed up with hot, dry weather and slow down with cool, wet weather,” he says. “If your corn has started ‘firing’ from the bottom up, and you have greater than four to five brown, dry leaves, the moisture content may be reached for the desired level of harvest.”

Visit NDSU Extension’s “Harvesting, Storing and Feeding High-moisture Corn” publication for more information.

Source: North Dakota State University