Ensiling involves many different components to ensure a successful harvest and high-quality, safe feedstuff. Often, producers get in a hurry and make a big mistake right off the bat—harvesting too early, resulting in very wet feed.
Recommended Moisture Levels
Ideally, corn silage should be ~62 to 68% moisture at harvest, or at approximately ¾ milk line, but this target changes a bit depending on how you intend to store the feed (Table 1). Although some cornfields may appear stressed, plants are likely wetter than one would assume. Leaves only make up a small portion of total corn plant moisture, the stalk and kernels contribute most to moisture levels.
| Silo Structure | ||
|---|---|---|
| Bunker Silos/Drive Over Piles | ||
| Bag Silos | ||
| Upright Concrete Stave | ||
| Upright oxygen Limiting |
*Trigger: Kernel milk stage to begin checking silage moisture.
Determining Whole-Plant Moisture
Although milkline can be used as a tool to indicate the rate at which dry down is happening, it does not always reliably provide an indication of whole-plant moisture. A Wisconsin study by Dr. Joe Lauer looked at over 800 farms and found very little relationship between kernel milkline and moisture due to the wide variability of corn hybrids at particular milk line points. For example, the study found that at 50% milk, some hybrids were at 50% plant moisture and others were as high as 74% moisture. This is why it is suggested to use kernel milkline as a trigger to begin testing for whole plant moisture; in fact, kernel milkline triggers correlated with moisture too high for proper ensiling in more than 95% of the hybrid environment cases evaluated in the Wisconsin study.
Once whole plant moisture is determined, an average moisture dry down rate of 0.5% per day can be used to predict when to start harvesting. In order to properly test for moisture, use either the microwave method or a Koster Tester. For specific instructions on using these methods, see the article, Silage Moisture Testing Tips.
Packing Strategy
Another often-overlooked factor in silage production and storage is packing. If using a pile or bunker silo, good packing and covering are of utmost importance to ensure feed quality is preserved and dry matter losses are kept to a minimum. Eliminating porosity is the key; in order to do this, layers need to be kept shallow enough and packing time needs to be sufficient. Packing layers should not exceed 6 inches. In addition, pack density should exceed 15 pounds of dry matter/cu. ft. In order to keep up with choppers and achieve these goals, more pack tractors may be needed.
Pounds Needed for Packing
To calculate pounds needed to achieve packing density, use the following equation:
- [Tons of silage delivered to pile per hour] × [a constant of 800 lbs.] = lbs. needed for packing.
- Example: 100 tons AF per hour × 800 = 80,000 lbs. (not counting push tractors).
Over-packing a pile is very hard to do, with the exception of the top layer. Spending excess time on the top layer of the pile or bunker does very little to pack the entire pile and may cause issues by rupturing plant cell walls, exposing nutrients and moisture to aerobic spoilage organisms.
Benefits of Covering
Piles should be covered as soon as possible following packing with oxygen barrier field and plastic. A 2011 study put together by Michigan State University Extension calculated the benefits of silage tarp by taking into account: the cost of plastic ranging from $0.115 to $0.120/ft.2, the labor included to put the tarp on the 12x80x140-foot bunker, and the initial cost of cut tires to cover tarp; this was weighed against $60/ton as fed corn. With a 30% loss in the top three feet of the uncovered bunker used in the study (totaling 201.6 tons of ‘as fed’ loss), losses amounted to near $12,096. Another 2 to 3% loss was assumed across the entire pile for closed ends and sides, creating an additional $3,226 in losses. Considering total losses of $15,322 against the cost of covering at $1,746, a net benefit of $13,575 was found in favor of covering. This is a 7.8:1 return on investment. Research done at Kansas State University showed very similar results. Long story short, although they may be a pain, silage tarps pay off by preserving the feed you worked hard to grow and put up.
Resources
- Lauer, J. Kernel Milkline: How Should We Use It For Harvesting Silage?. 1999. University of Wisconsin.
- Silage Zone Manual, Third Edition. 2018. PHII.
- Thomas, C. Should you cover your bunker silo? . 2011. Michigan State University Extension.
