Silage leachate: An environmental disaster

Proper handling of silage leachate can decrease your farm's impact on water quality.

Silage leachate is an issue for all farmers who have silage. Silage leachate can come from all forms of silage storage: bunkers, upright silos, bags, and piles. Handling leachate can be simple or complex depending on the scope of your operation.

Silage leachate is an organic liquid that is formed when water, or in some cases pressure from the structure, comes in contact with silage and runs off. Leachate can be formed as a part of silage storage, especially if the corn or alfalfa is harvested too wet. Water comes in contact with the silage because it is part of the silage. The other source of leachate is rain water coming in contact with silage and carrying nutrients with it. This leachate has a high biological oxygen demand, BOD. If silage leachate is allowed to reach surface water, oxygen in the water will be consumed so quickly that anything living in the water, including fish, could immediately be in peril. It is estimated that one gallon of silage leachate can lower the oxygen content of 10,000 gallons of river water to such an extent that there is a chance for fish kill. Leachate also can cause algal blooms that will further deplete the oxygen levels of surface water and it can also produce high levels of ammonia which will also cause fish kill.

Groundwater is not immune to the hazards of silage leachate. Leachate can increase water’s acidity due to its high nitrate-nitrogen levels. Another side effect of silage leachate in groundwater is a distasteful odor. Wells located within 150 feet to silage storage should be routinely checked for contamination such as nitrates and e.coli.

Farmers can implement practices to reduce the amount of leachate produced and its impact on the environment. Make sure that the moisture content of corn silage is between 65% and 70% for bunkers. Moisture levels may be even lower for corn silage stored in upright silos, though it should not fall below 62%. Alfalfa haylage should be harvested at 60% to 70% moisture content Contact between silage and water can be minimized by utilizing plastic covers to divert water off of the silage area. See a recent MSUE News for Ag article by Craig Thomas for more information about the economic benefits of covering silage.

Make sure that the water is not running along the sides of the bunker and coming into contact with feed. If these measures are not enough to impede leachate movement off site then engineered practices need to be implemented. Grassed filter strips or diverting leachate into an existing or new holding facility may be needed. If you are interested in an engineered practice contact your local Natural Resource Conservation Service. For more information about recommended practices for silage harvest and storage contact your local Michigan State University Extension office and ask for the contact information for your forage or dairy educator.