A better way to store silage

Protect feed quality and reduce environmental risk.

A picture of a silage drop off
Bunker sile. Photo by Sarah Fronczak.

Farmers impacted by excessive rain and flooding during planting season may be turning to silage to replace grain feed stocks. It is important to remember that silage leachate--the juice that comes off silage, and runoff from silage piles typically carry high levels of nutrients away from the feed. This runoff can get into surface and groundwater causing water quality concerns and loss of feed quality. It typically contains high concentrations of nitrogen--in the form of ammonia, phosphorus, and sugars. These nutrients can become food for algae and other plants in surface water leading to algal blooms and fish kills. Also of concern, is the low pH of silage and its damaging effects on the concrete of your storage facility? There are some things you can do to protect your ensiled forage and water quality.

Moisture Content

The moisture level of the forage being ensiled plays a big role in the amount of leachate produced. Make sure to harvest at the proper moisture content for each type of silo.  The moisture content of corn silage should be 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 this can be achieved by natural wilting. Another way to reduce leachate loss if through the addition of adsorbent materials such as barley straw and sugar beet pulp. According to the article, Silage effluent management: A review, these materials have been shown to be effective to improve feed quality and fast weight gain.

Silo Construction

Silos should be watertight to prevent precipitation from reaching the ensiled crops. Any holes in silo bags should be patched immediately. Plastic covers on bunker silos can be helpful, however the silage and the walls of the silo need to be covered to prevent water from running down the sides of the silo. Constructing a roof over a bunker silo and feed pad can be highly effective. Keep in mind that corrosion resistant materials should be used since leachate is destructive to metals and concrete. According to the article, Evaluation of mix specification and PFA as a cement replacer in concretes used in silage storage structures, for silo walls found that concrete mixes prepared with cement contents of 20.3 and 23.4pounds per cubic foot (547-632lb/yd3) and water: cement ratios of 0.55 and 0.50, respectively, had the lowest mass loss after 10 years. According to the article, Resistance of geopolymer and portland cement based systems to silage effluent attack, geopolymer mortars and pastes are showing promise to replace Portland cement, although not widely used for silage storage currently. These recommendations are based on current research, but may or may not prove to be cost effective on your farm.

A drainage system should be installed in the silo to allow the leachate and runoff to be collected and treated. All flows from the silo should be collected. Collections tanks should not be located near surface water or wells. When sizing storages estimate volumes of 3y3 of leachate for every 100ton of silage ensiled at 70% moisture content. Additional storage will be needed to accommodate for any precipitation that can’t be diverted. A low flow/high flow bypass system can greatly reduce the amount of storage needed by only capturing the more concentrated flows at the beginning and end of a storm. 


A common disposal practice is to divert the effluent to a liquid manure storage, however this should be done with caution due to the large amounts of Hydrogen Sulfide (H2S) that can be released. Land application normally follows storage of silage leachate with manure. Testing of manure + leachate is highly recommended due to the potential for vegetative burning. Land application should be done according to a nutrient management plan.

Other methods for treatment include constructed wetlands and vegetated treatment areas, however studies suggest that the function of these treatment areas can be compromised by concentrated effluent. 

If you are interested in an engineered practice discussed in this article 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.

MSU Extension offers additional educational resources and programs to help farmers as they deal with delayed planting seasons at https://www.canr.msu.edu/agriculture/delayed-planting-resources.

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