Improving feed quality of silage piles will also protect the environment
The same management practices that cut down forage shrink and improve feed quality also reduce silage leachate after harvest and contaminated runoff year round.
Below are some harvest and management reminders for quality silage:
Harvest moisture: Manage harvest moisture of all ensiled feedstuffs very closely to reduce leaching potential. Typically, 30 percent is the minimum dry matter content for leachate prevention, but records, observation and experience will provide the most accurate thresholds for each particular feedstuff.
Compaction: Exclude oxygen and increase forage density with adequate packing when filling. Greater silage density will also improve the storage capacity of all structures, thus requiring less total storage area to manage. A thumb rule for good compaction is 800 pounds of packing tractor operating continuously per ton of feed harvested per hour. Pack no more than six inches at a time in a progressive wedge fashion.
Shape: The shape of the pile within the storage is also important and should be sloped to divert water off the pile. For instance, divert water away from walls to avoid penetration of water into feed along the wall. Avoid overfilling bunker silos to better enable adequate compaction and water diversion.
Covering: Covering should be done in a manner to minimize, if not eliminate, water and oxygen penetration of the feed. This may include innovative covering practices such as a continuous plastic barrier from the top of the pile to between the wall and the feed. This practice is sometimes called enveloping which involves draping the plastic over the walls prior to filling. Once the feed is compacted into place, fold the plastic over the top overlapping the seam prior to adding tire sidewalls or equivalent weights.
Face management: Maintaining a smooth vertical feedout face will preserve feed quality, reduce wasted feed and minimize the production of contaminated runoff. Avoid knocking down more feed than is needed on a given day.
Housekeeping: Avoid piling waste or excess feed on the silage pad. Maintain a smooth pad surface and clean up spilled feed with a broom or scraper on a daily basis. A clean surface is especially important when rain is in the forecast to minimize the production of contaminated runoff.
Emergency planning: Provisions should be made for times when feed is inadvertently or unavoidably harvested and stored at higher than desired moisture content. This may include a small dry weather leachate collection basin or something as simple as utilizing sawdust to soak up leachate until it stops running.
Leachate a major pollutant
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 results 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 is often reduced such that vegetative buffers are adequate to protect any nearby surface waters.
For more info, see the Environmental Stewardship: Controlling Silage Leachate.