Study

Filamentous algal control using barley straw

Summary

Action: Use barley straw to control algae

A controlled study in 1990–1993 in a canal in Ireland (Caffrey & Monahan 1999) reported that adding barley straw to control filamentous algae facilitated growth of whorled watermilfoil Myriophyllum verticillatum. After 18 months, “localised stands” of watermilfoil appeared in a stretch of the canal treated with barley straw. After 33 months, watermilfoil reached 25% cover and 85 g/m2 biomass in the treated stretch. No watermilfoil was present in an upstream, untreated stretch. In all 12 comparisons between 6 and 33 months after first adding barley straw, the treated stretch contained significantly less filamentous algae (0–14 g/m2) than the untreated stretch (24–120 g/m2). Methods: The study used two adjacent 1-km stretches of a canal susceptible to nuisance growth of filamentous algae. Barley straw (loose floating bales, equivalent to 10 g/m3) was added to the downstream stretch in October 1990. Further straw was added every 4–7 months until February 1993. The upstream stretch received no barley straw. Biomass (above- and below-ground) was sampled with a plastic “stovepipe” every 2–3 months (except winter), from October 1990 to July 1993. It was dried before weighing.

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