Barley Straw - Tech Talk 37
Research through Aquatic Weeds Research Unit U.K. indicates that barley straw is highly effective in the control of algae. How about that? An organic approach to algae control! It takes six to eight weeks for barley straw to become active after it is placed in moving water. After that, barley straw will remain an active algaecide for approximately six months. Microbial growth, oxygen and warm water temperatures activate the decomposition of the straw. With sufficient water flow through the straw, lignins oxidize into homic acids and, with sunlight and oxygen, destroy algae, with no effect on higher plant and aquatic life.
Barley straw decomposes slowly, so its oxygen demand does not cause problems unless an excessive amount of straw is used. Stagnant water will go anaerobic inside the straw bundle, killing the microbes, so be sure to keep the water moving.
How much barley straw to use? Barley straw is most effective in shallow (1 m) water with sunlight and good circulation. Clear water needs less straw, but with turbid, muddy water and less sunlight, more straw is required. Low temperatures are less effective.
Water surface area is used to calculate dosage. In still water ponds, the minimum quantity of straw needed to control algae is 2.5 grams (.09 oz) of straw per square meter of water surface. In water with a severe algae problem, high first treatments up to 50 grams (1.8 oz) per square meter may be required. Start with small quantities and monitor effects. Barley straw may be prestarted in nonalgae problem areas with good oxygenated water flows.
The research unit suggests you tie the straw in small bundles, make flat sheaves or stuff it into net bags. Weight or stake them to the bottom in an area with water movement.