Undiluted silage leachate or seepage is very acidic and highly corrosive. It will eat away the concrete of feed storage structures and burn most any vegetation that it contacts. Leachate also tends to be very high in nitrates, thus it may be a risk to groundwater if allowed to pond in low areas.
Silage leachate’s extremely high biological oxygen demand (BOD5) makes surface waters among the most vulnerable to its impact. Because of the high BOD5, as little as one gallon of pure silage leachate per 10,000 gallons of river water may reduce oxygen to a critical level for fish survival. There have been numerous documented cases of fish kills in streams and ponds caused by silage leachate worldwide.
Although producers are most familiar with leachate that occurs immediately after harvest, any time precipitation hits the feed it can create contaminated runoff. The runoff may be relatively low in nutrient content, but it is still considered a pollutant if it reaches ground or surface waters.
A common recommendation, or requirement in the case of some permitted farms, is to capture silage leachate and contaminated runoff from feed storage areas in a storage pond for later application to crop land. This approach can be effective; however, it frequently becomes a logistical and economic nightmare. Precipitation events on a large surface such as a feed storage area often result in millions of gallons of low contaminant water stored in expensive structures and in need of costly field application.
Prevention works best
The alternative to collecting all leachate and runoff from silage areas is to simply prevent its production in the first place. The same strategies that prevent silage leachate and contaminated runoff have economic returns in reducing shrink and improving feed quality. Studies have shown that improper management of bunker silos can result in dry matter losses greater than 30 percent in the top three feet. Furthermore, the inclusion of spoiled feed from storage in feed rations will likely reduce feed intake and animal performance.
Leachate also directly removes nutrients from the forage, particularly soluble nitrogen and carbohydrates. These principles are not only true for corn and hay silages but they apply to other high-moisture feedstuffs such as high-moisture corn and wet distillers grains.
By implementing basic management practices, feed leachate and contaminated runoff can be minimized, while feed preservation and quality are maximized.
Like so many of the risks the livestock industry faces, prevention is the best cure for a problem. By implementing these practices, the contaminated runoff and diluted leachate are often reduced such that vegetative buffers are adequate to protect any nearby surface waters.
For more info, see the Environmental Stewardship: Controlling Silage Leachate.
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