Making quality corn silage
It’s hard to believe it is already August, but the weather and the calendar both tell me fall is right around the corner. In this week’s column I’ll give you a few pointers on making quality corn silage.
1) Put up silage at the correct moisture level
Depending on the storage structure you are using, corn silage should be harvested at 65 to 70 percent moisture for optimum results. Moisture levels that are too low result in less favorable fermentation and in poor packing characteristics in the silage; whereas moisture levels that are too high result in silage that has greater effluent losses (loss of nutrients in the water which oozes from the pile) and in a “sour” fermentation. Corn silage can be harvested at slightly lower moisture levels for upright oxygen limiting structures.
The kernel milk line is one way to gauge approximate silage readiness in corn. When you cut or break a corn cob in half, the kernel milk line is the line that is visible between the dry starchy and the liquid or milky portion of the kernel which hasn’t matured. At 50 percent kernel milk line, silage moisture averages 63 percent, according to University of Wisconsin data. If the milk line is closer to the top of the kernel (less starchy material visible), the plant is wetter. As the plant matures, the line (and the starchy material) moves closer to where the tip of the kernel attaches to the cob.
Ideally, kernel milk line should be used as an indicator of when to begin monitoring whole plant moisture content. Once kernels are dented and the milk line forms begin monitoring moisture content to ensure you make accurate decisions on when to begin silage harvest.
There are variations in kernel milk line traits relative to variety, growing conditions, etc. Therefore, a more accurate method to determine moisture content is by using a microwave oven. For more details on how to properly conduct this procedure, see this Web site: http://www.agry.purdue.edu/ext/forages/publications/ID-172.htm
2) Determine proper cutting height
Cutting height impacts both the quality and quantity of silage produced. Harvesting at a lower cutting height increases dry matter yield but does so with the addition of lower quality forage material (lower portions of the stalk). Raising the cutter bar height will increase the quality of the silage slightly (lower proportions of NDF and ADF and a slightly more digestible silage) but will lower the overall dry matter yield. These aspects are more important in dairy operations or when silage will be used as a primary ingredient in growing rations.
Cutting at an increased height may be beneficial in reducing the nitrate content of the silage crop since nitrate tends to accumulate in the lower portions of the plant. Keep this in mind when you harvest silage during drought.
3) Pack the silage correctly
Excluding oxygen is a very important aspect of making good quality silage. Proper packing ensures that oxygen is driven out. Adequate packing involves a number of different factors including the correct chop length for your particular silage crop, as well as having the appropriately sized tractor for the amount of silage you are placing in the pile. Because wheeled tractors exert more pressure per square inch compared to crawler or track-type tractors, wheeled tractors are preferred for packing silage. Be sure to use caution when packing silage. The weight of the tractors used and the height of many bunker silos make this a job for experienced tractor operators. Add thin layers of material and pack adequately as the silo is filled.
One often overlooked item is the importance of sharp knives during the chopping process. Sharp knives produce a uniform chop length and improve packing in the bunker. Take time before and during harvest to sharpen the knives. It will pay dividends in improved silage quality.
The silage making process also involves making the correct sized silo face (the face you will feed from) relative to the amount you plan to feed on a daily basis. This ensures minimum spoilage when the silo is opened and the face is exposed to oxygen during the feeding process.
Kernel processors are gaining popularity across the region. The processors should be set so that all the kernels are broken. The portions of the cob which are visible should be no larger than the end of your little finger. If your machine requires adjustment to achieve these results, be sure you follow all the safety procedures recommended by the manufacturer.
4) Cover the pile
Covering the silage bunker after packing is complete ensures that spoilage will be minimized and that potential damage from rodents and other wildlife will be kept to a minimum. Black or white plastic can be used. Use plenty of tires to adequately hold the plastic on the bunker silo.
By following these few pointers when you put up corn silage this fall, you will improve the quality of the silage, experience lower storage losses, and, possibly, experience improved animal performance.
Greg Lardy is the head of the NDSU Animal Science Department.