Harvesting alfalfa silage involves specific steps to ensure optimal preservation of nutrients and quality, which are crucial for maintaining the health and productivity of livestock. Here’s how alfalfa silage is typically harvested:
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Timing of Harvest:
- Choosing the right time to harvest alfalfa for silage is crucial. The best time is usually at early bloom stage for first cuttings or late bud stage for subsequent cuttings. This stage provides a good balance between maximizing yield and maintaining high nutritional content. Harvesting at the right stage also ensures the right moisture content, typically between 60-70%, which is ideal for proper fermentation.
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Mowing:
- The alfalfa is cut close to the ground using a mower or mower-conditioner. Mower-conditioners are particularly useful as they not only cut the alfalfa but also crimp the stems. Crimping accelerates the drying process by breaking the plant’s stem surface, which facilitates faster water loss.
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Wilting:
- After mowing, the alfalfa is left in the field to wilt for a short period. This step is crucial to reduce the moisture content to the desired level for ensiling (ideally between 40% and 60%). Wilting time will depend on weather conditions; sunny and breezy weather can speed up the process.
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Chopping:
- Once the alfalfa has wilted to the appropriate moisture content, it is harvested using a forage harvester that chops the alfalfa into small pieces, typically about 3/8 to 1/2 inch long. Proper chopping is essential for effective packing and fermentation as it increases the density of the silage, reducing oxygen levels and promoting anaerobic conditions.
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Transporting and Storage:
- The chopped alfalfa is quickly transported to the silage storage area to minimize exposure to air. Common storage facilities include bunker silos, drive-over piles, or silo bags. The choice of storage depends on the farm size, amount of silage, and available resources.
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Compacting and Sealing:
- The chopped alfalfa is compacted in the silo or pile to expel as much air as possible. This compaction is typically achieved by repeatedly driving heavy machinery over the pile. After compaction, the silage is covered with a plastic sheet or directly sealed in silo bags. This cover is often weighed down with tires, sandbags, or silage covers to ensure it remains airtight.
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Fermentation:
- Once sealed, the alfalfa undergoes an anaerobic fermentation process that lasts at least three weeks. During this time, bacteria ferment the sugars in the alfalfa to produce lactic acid, which lowers the pH and stabilizes the silage, preserving its nutritional quality.
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Feedout:
- When feeding the silage, it is crucial to manage the silage face properly. Keeping the face smooth and tight reduces exposure to air, preventing spoilage. It is recommended to remove silage at a rate that prevents the exposed silage from heating and spoiling.
Each step in the process of harvesting alfalfa silage is critical to ensure the final product is of high quality, providing valuable nutrition to livestock efficiently and cost-effectively. Proper management from cutting to feedout helps maintain the integrity and nutritional value of the silage.