Virginia Farmstead Assessment System*

Fact Sheet No. 12 Silage Storage and Management

Fact Sheet and Worksheet No. 12 were modified by Eldridge Collins (Biological Systems Engineering Department, Virginia Tech).

Technical Reviewer: Russ Perkinson (Virginia Division of Soil and Water Conservation, Richmond, Virginia).

Publication Number 442-912, June 1996

*Overview of the Virginia Farm Assessment System

Table of Contents

Introduction
I. Silage Moisture Content
II. Silage Storage Location
III. Silo Design and Construction
IV. Leachate Collection and Disposal
Contacts and References
Worksheet No. 12

Introduction

Silage can be made from corn, grain, or alfalfa, or from canning wastes, such as those resulting from sweet corn processing. The amount of leachate (silage juices) produced varies with the material stored, its moisture and nitrogen content, and handling and storage conditions. Of these, moisture content is the most crucial.

Most harvested silage can be characterized as low-moisture because the crop is usually allowed to wilt to the proper moisture content before chopping to ensure proper ensiling. In general, silage put into horizontal silos is typically at a higher moisture content. Haylage stored in tower silos has been reported to produce significant amounts of silage juice. In Virginia, corn silage storage and associated leachate is regulated as an agricultural waste. Farmers must take steps to assure that discharge does not occur to surface or groundwaters. (See Figure 1).

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I. Silage Moisture Content

Research indicates that silage stored at 65 percent moisture content or higher can produce leachate. For grass silage, the amount produced varies from a trickle at 75 percent moisture content to 79 gallons per ton at 85 percent moisture content. About three-quarters of theleachate is produced in the first three weeks of storage, although it can continue to flow for up to three months.

Several methods are available to reduce leachate production from silage. The most effective of these is to allow the crop to wilt for 24 hours. Although this may not always be possible in Virginia's humid climate, available data shows that the practice can reduce silage moisture content by 10 percent and leachate production by 100 percent. Other leachate control methods include varying cutting and harvesting times, cutting or crimping the materials, or adding moisture-absorbent materials to the silage during storage.

Adding absorbent materials not only reduces leachate, but it also raises the nutrient value of the silage. Absorbent materials that can be used include oat meal, dried sugar beet pulp, dried corn cobs, ground corn, newsprint and bentonite clay. Most of these materials can absorb moisture at one to three times their weight. To be effective, enough material must be added to absorb the anticipated leachate

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II. Silage Storage Location

To prevent possible groundwater contamination, silos should be located as far away from wells and springs as practical. State regulations require that plastic storage tubes be at least 8 feet away from a well, and that new glass-lined silos be at least 50 feet away from a well. Silos with a pit, or without a pit but with a concrete floor and drain, must also be at least 50 feet from a well. Earthen trenches or pits must be at least 250 feet away from a well. Minimum separation distances regulate new well installations. Existing wells are required by law only to meet separation requirements in effect at the time of well construction.

Sweet corn silage storage sites must meet soil absorption criteria and be located at least 1000 feet from a community well or 250 feet from a private well. Stacks must also be at least 5 feet above the water table and located on slopes of less than 2 percent. Any leachate from the stacks must be managed to prevent surface or groundwater contamination. Storage sites should be located outside of environmentally sensitive areas such as those of fractured bedrock, high water tables, or in close proximity to streams, ponds and springs. The DEQ has authority to require groundwater monitoring. These standards do not apply to stacks of less than 150 tons.

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III. Silo Design and Construction

Silo construction for most agricultural uses is not regulated in Virginia. Most silos being built today have interiors made of concrete or, in the case of oxygen-limiting silos, a glass-like coating over steel. Silage stored in glass-lined silos typically has a lower moisture content and poses a low risk of groundwater contamination. It is possible, though, for some liquid to leak out.

Silo bags generally store silage of higher moisture content. Liquid can pool in the bag and spill out when opened. Horizontal trench silos excavated into the ground may affect groundwater, especially in coarse soils when close to the water table. Properly compacted clay soils and concrete floors can limit leachate seepage.

The type of silo often has less effect on the potential to contaminate groundwater 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 a concrete floor (See Figure 2). Older structures can be relined to make them relatively watertight.

Silo caps or covers keep rain water from entering the silage, preserve a quality silage, and reduce the potential for producing leachate. Horizontal silos are covered with a plastic sheet and old tires are used to keep the cover in place.

It is important to divert clean water away from new and existing silage storage structures. For both vertical and horizontal silos, diverting clean water away from silage can protect both groundwater and surface water.

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IV. Leachate Collection and Disposal

Leachate can be collected from tower and horizontal silos by channeling the liquid into a water retention structure, usually a pond lined with concrete, clay, or plastic. Horizontal silos use channels to direct seepage into a collection area. Contact your county Extension office for assistance with design.

The most cost-effective leachate disposal method is land spreading. Nitrogen in leachate has significant fertilizer value that can be used if applied during the growing season. Because of its high nitrogen and organic content, leachate can burn plant tissue and deplete soil oxygen. Farmers who consider land spreading should consult a soil specialist to determine how much leachate can be safely spread on each field. Contact your local Natural Resources Conservation Service or county Extension office for assistance.

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Contacts and References

For review of construction plans and regulatory requirements, contact the Regional Office of the Virginia Department of Environmental Quality (DEQ).

To design a land application/wastewater treatment system, contact the Natural Resources Conservation Service (NRCS), private consultants, or the Biological Systems Engineering Department at Virginia Tech, Blacksburg, Va.

Acknowledgements.

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Go to Silage Storage and Management Worksheet No. 12.

Visit Virginia Cooperative Extension.

View a list of the Virginia Farmstead Assessment System publications.