The Efficacy of Red Oak Sawdust as a Mulch to Control Grass and Weeds in Organic Wild Blueberries
Weeds are a major problem in wild blueberry fields. Some landowners control them with herbicides, but for those who want to raise an organic crop there is little alternative to weeding by hand, which requires a lot of labor and is consequently expensive. Mr. Johnson noticed that where his blueberry fields verged on stands of red oak, weed populations appeared to be diminished, but not the density or vigor of the blueberry plants. He hypothesized that the red oaks had an allelopathic effect, to which the blueberries were immune. He further supposed that if the living trees could suppress weed populations, perhaps he could achieve the same effect by applying red oak sawdust to his fields.
The Johnsons applied sawdust to a depth of 1½ inches on two weedy plots in a blueberry field near Ellsworth, Maine, and left two other plots untreated. They made the application in April, and the following October took a census of the weeds. They estimated the fraction of ground cover of all the weed species taken together at 72% in the untreated plots, and 57% in the treated plots, while the fraction of cover accounted for by the blueberries remained essentially unchanged, at approximately 16%. They are continuing the experiment, and will collect yield data this year.
Maine Organic Farmers and Gardners
Augusta, ME 04338-2176