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Harvesting corn silage at the right time is critical to obtain a high yield and quality product. Moisture content of the silage is the most important consideration, but how it is chopped is also important. Monitoring throughout the harvest helps to ensure a good quality silage product.
Regardless of the corn products relative maturity, there is little variation from silking to harvest between products. The most difference in corn products occurs in the length of time between emergence and silking. Once silking occurs in a field, the crop will generally be ready for silage harvest about 35 to 47 days later. This indicator can be used to begin staging fields for silage harvest.
Harvesting at the proper moisture content is the main goal during silage harvest. Ideally, corn silage should have 60-70% moisture content (30-40% dry matter) at harvest. Once the dent (R5) stage occurs, the field should be checked for kernel milk stage development. This can be done by breaking a corn ear in half and looking at the kernels (Figure 1). There will be a line where the solid and liquid parts of the kernel are separated, and this lines moves from the outer edge of the kernel toward the cob of the ear with maturation and drying. At 1/2 milk line, the crop could be at about 65% whole-plant moisture and ready for silage harvest. However, there can be a lot of variation in the moisture content, and using the milk line progression has not been shown to be a very accurate guide to determine when silage harvest should begin. Therefore, sampling for accurate whole-plant moistures should begin once the kernel milk line begins to move from the outer edge of the kernel. Monitoring the moistures throughout harvest helps to get the best balance between yield, starch, and dry matter of the silage crop. Harvesting the crop too early (corn silage at moisture levels above 70%) when it is too wet or immature results in reduced yield and starch content. Ensiling corn that is too wet can also lead to poor fermentation and substantial seepage and storage losses. As a result, the silage could be foul-smelling having poor feed quality, palatability and intake potential.
Harvesting the crop late when it is too dry can result in poorly packed bunkers and piles. Silage packed too dry can have air pockets preventing an anaerobic environment and allowing molds and spoilage to occur. The silage will have more starch content, but will be lower and digestibility and overall feeding quality.
Figure 1. Showing the milk line which has moved about 1/2 the way down the kernel.
Harvesting at the right time provides the best whole-plant digestibility with the energy coming from the starch. Corn with excellent late-season plant health, stalk strength and standability will generally provide the highest quality silage when harvested at the proper time. Along with harvesting at the proper time, good fertility and disease control helps to reduce the levels of mycotoxins in silage.
Good chopping practices should be followed when harvesting corn silage. Well-maintained harvesters with sharp knives is essential. Corn silage should be cut into 1/2 to 3/4 inch pieces for good packing. Kernel processing while harvesting can also be important for obtaining high quality corn silage. Processing occurs through the use of rollers which further processes the silage after it has gone through the knives. The benefits of processing is greatest when the crop is drier or harvest has been delayed. Along with periodically checking moisture content, the settings for length of cut and roller openings for processing should be checked and adjusted during harvest.