Algae color the water green or brown and uncontrolled growth can lead to nuisance surface scums, poor water quality, noxious odors and an overall reduction in the ponds recreational, and aesthetic value. Excessive levels of algae occur when nutrients, especially phosphorus, are abundant. After taking steps to reduce the amount of phosphorus entering a pond, it may be desireable to control the algae growth directly. Typically this is accomplished by treating the lake with copper containing herbicides. These treatments are effective short term controls of algae, but they are also toxic to non-target organisms that are important food sources for fish.
Barley straw has been used with varying success in ponds throughout the United States and England as a method of controlling algae. As the straw decomposes in the pond, it releases a chemical which inhibits algal growth. Although years of research and anecdotal evidence have revealed that barley straw has varying effects upon algae control, the fact that it is a relatively cost effective and an environmentally acceptable way to control algae in ponds makes it a technique worth considering in acreage ponds.
Barley straws effectiveness is dependant upon complete decomposition and a release of the growth inhibiting chemical. When water temperatures are below 50°F, it takes approximately 6-8 weeks for the straw to produce enough growth inhibiting chemical to effectively control the algae. However, it only takes 1-2 weeks when water temperatures are above 68°F. Once the straw produces sufficient amount of the chemical, it is likely to control algae for about 4-6 months. Therefore, straw should be applied in mid-late April in order to control summer growth in Nebraska acreage ponds.
The amount of straw required to control algal growth depends on the surface area of the pond. The recommended rate for ponds with a history of algae problems is 225 lbs. Of barley straw per acre.
For the barley straw to be effective the bales must be broken apart. Bales packed too tightly do not allow adequate water movement through the straw, inhibiting straw decomposition and chemical release. The loose straw should then be placed in some form of netting or loose woven sack (i.e. onion sacks). Then use floats to suspend the straw filled netting in the upper 3 to 4 feet of the pond. The straw loses its effectiveness if it sinks below this depth.
Water movement near the surface will keep the straw well oxygenated and distribute the growth inhibiting chemical throughout the upper portion of the pond. This ensures that the chemical is produced where the majority of the algae are growing and away from the bottom sediments which will inactivate the chemical. Therefore, it is recommended that floats be inserted inside the netting at the same time the netting is filled with straw. The netting is then anchored into place using rope attached to bricks or concrete filled buckets.
In order top improve the distribution of the growth inhibiting chemical, it is recommended that nets be placed equidistant from other nearby nets and the shore. The placement of the nets does not need to be exact and practical considerations must be considered. On small ponds where only one net of straw is required, place the net in the middle of the pond.
Source: Tadd Barrow, University of Nebraska
