Rockingham County Conservation District

110 North Road Brentwood NH 03833-6614

603-679-2790   Fax: 603-679-2860

website: www.rockinghamccd.org

email:   rccd@rockinghamccd.org

Using Barley Straw In Ponds

Excessive algae growth is one of the most common problems occurring in ponds.  Traditional mechanical and chemical control methods are not always efficient or economical.  In recent years, the use of barley straw has become more common in other parts of the country as an alternative method for reducing excessive algae growth.  When applied at the proper time and rate, barley straw has been very successful in ponds.

How does it work?

Barley straw does not kill existing algae but it does inhibit the new growth of algae.  It seems that barley straw, when exposed to sunlight and in the presence of oxygen, produces a chemical that inhibits algae growth.  Barley straw does not reduce the growth of other aquatic plants.  In fact, in some cases aquatic plant growth has increased after barley straw applications because algae are no longer present to compete with the aquatic plants.  Activity is only produced if the straw is rotting under well oxygenated conditions.  Usually, there is adequate dissolved oxygen in water to ensure that the chemical is produced by the straw.  However, if the straw is applied in large compact masses (such as a whole bale) or to very sheltered and isolated areas of water, there will be insufficient water movement through the straw, which will progressively become anaerobic (without oxygen).  Under these conditions, only the surface layers of the straw will produce the chemical and so the majority of the straw will have no useful effect.

When should it be applied?

Barley straw is most effective when applied early in the year prior to the appearance of algae (fall through early spring).  When applied to cold water less than 50EF it may take six to eight weeks for the straw to begin producing the active chemicals that inhibit algae growth.  If the straw is applied to warmer water above 70EF, it may become effective in as little as one to two weeks.  Larger filamentous algae can survive for longer periods and may not be adequately reduced in the first season if the straw is added too late in the growing season when algae growth is dense.  It is preferable to add the straw very early in the spring before growth starts.  In any case, barley straw remains effective for approximately six months after application.

How much straw should be used?

The most common application is about two bales per surface acre of pond.  (A bales weighs approximately 40-45 pounds.)  The depth of water is not important.  However, when a water body with a history of severe algal problems is first treated, a higher dose is preferable, two or three times the recommended amount.  Once the algal problem has been reduced, and further additions of straw are being made to prevent a recurrence of the problem, the dose can be reduced.  Overdosing the pond with barley may cause fish kills because the straw deoxygenates the water as it decays.  This is especially a problem if the pond is overdosed with straw during a prolonged warm spell.

To help you in determining how much straw to use, there are 43,560 square feet in one acre, 21,780 square feet in half an acre, 10,890 square feet in a quarter acre, and 4,356 square feet in a tenth of an acre.  Use two bales per acre, one bale per half acre, one half bale per quarter acre, and 4-42 pounds per tenth of an acre.

How should the straw be applied?

The straw is most effective when applied loosely in cages or netting.  It is best to anchor the straw packages to the bottom but provide a float to keep the straw near the surface of the pond where sunlight and oxygen are more prevalent.  It is best to apply the straw at several locations around the pond and especially near the water source if a spring or stream feeds the pond.  In small garden ponds, small nets or nylon stockings can be used to hold the small amounts of straw needed.

Are there any downsides?

Barley straw needs sunlight and oxygen to work properly.  Muddy or stagnant water will reduce the straw=s effectiveness.  Existing growth of surface algae will also reduce the effectiveness by reducing both sunlight and water circulation.

Where can I get barley straw?

The Rockingham County Conservation District sells barley straw for $12 per bale.  For more information please contact the District office at 679-2790 or email us at rccd@rockinghamccd.org