Indiana Farmstead Assessment for Drinking Water Protection
Introduction Silage moisture content Silage storage Silo Location Silo design & construction Leachate collection and disposal Authors
Silage Storage Survey
The risk of groundwater contamination due to silage storage is rela-tively low; however, contamination can occur if silage leachate (silage juices) enters a well or seeps through the soil to shallow groundwater. Surface watercan easily be contaminated by leachate runoff from a leaking silo or a ground storage bag. A producer can reduce these risks by managing silage moisturecontent and maintaining a sound storage structure.
Silage can be made from corn; silage crops, such as grain or alfalfa; and canning company wastes, such as from sweet corn processing. The amount of leachate produced varies with the material stored, its moisture and nitro-gen content, and handling and storage conditions. Of these, moistur e is the most critical.
Farmers can use several methods to reduce leachate production fromsilage. The most effective of these is allowing the material to wilt in the field for 24 hours. Although this may not always be possible in a humid climatelike Indiana's, it can reduce leachate production significantly. Adding absorbent materials, such as dried corn cobs or ground corn, will also reduceleachate production and raise the nutrient value of the silage.
Most harvested silage is characterized as low-moisture silage. The cropis allowed to wilt to the proper moisture content before chopping to ensure proper ensiling. Silage put into horizontal silos is typically at a higher mois-ture content. Haylage stored in tower silos has been reported to produce significant amounts of silage juice. Many older silos have dirt floors or havebeen dug into the subsoil 3-6 feet below gr ound level. However, new silos are built with concrete foundations and floors. Horizontal, pit or trench siloson bare ground can threaten groundwater if much leachate is produced.
To prevent possible well contamination, silos should be located as faraway from wells as practical. The Indiana State Board of Health recommends a minimum of 50 feet between a well and a silo (see Fact Sheet 1). Earthentrenches or pits should be farther away from the well. Do not allow silage leachate to runoff to surface waters.
Most silos being built today have interiorsmade of concrete or, in the case of oxygen-limiting silos, a glass-like coating over steel. Silagestored in glass-lined silos typically has a lower moisture content and poses a low risk of ground-water contamination. It is possible, though, for some liquid to leak out.
Silo bags generally store silage of highermoisture content. Liquid can pool in the bag and leak out when it is opened.
Horizontal trench silos excavated into theground may affect groundwater, especially in coarse soils and sites close to the water table. Compacted clay soils and concrete floors can limit leachate seepage.
The type of silo on your farm often has lesseffect on its potential to contaminate ground water than the condition of the silo. For example,an old wooden silo with an earthen floor poses a higher risk than a concrete horizontal silo with aconcrete floor. Older structures can be relined to make them relatively watertight.
Silo caps or covers keep rain water fromwetting the silage, which preserves silage quality and reduces the potential for leachate produc-tion. Cover horizontal silos with plastic sheeting and use tires to keep the cover in place.
It is important to divert clean water awayfrom new and existing silage storage structures. For both vertical and horizontal silos, divertingclean water away from silage protects groundwater and surface water.
Leachate can be collected from tower andhorizontal silos by channeling the liquid into a water retention structure, usually a pond linedwith concrete, clay or plastic. Drain tiles around tower silos can be used to collect any seepagefrom the silo. Horizontal silos use channels to direct seepage into a collection area. Contact yourcounty Extension office for assistance with design.
The most cost-effective disposal method island spreading. Nitrogen in leachate has significant fertilizer value if applied during spring orearly summer. Because of its high organic matter content, leachate can burn grasses and removeoxygen from the soil. Farmers who consider land spreading should consult an agronomist orExtension educator to determine the proper application rate.
Don Jones, Agricultural Engineer
Editor: Cheri Janssen, Department of Agronomy
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Silage Storage Survey
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