“Sweeping” Weeds Off the Wheat Field

A specially designed cultivator can help Pacific Northwest wheat growers “sweep” away about two-thirds of their potential downy-brome problem--up to a year before the costly weed could otherwise take over their wheat fields.

Downy brome and other bromes infest 14 million acres of western winter wheat and cost growers $300 million a year in lost yields.

The broad, flat sweep cultivator makes weed seeds germinate quickly, scientists with USDA’s Agricultural Research Service say. Weeds then can be killed by herbicide or cultivation in the fallow year.

If growers don’t act, the scientists warn, the seeds stay dormant through winter and germinate the next fall, when wheat is again planted.

On January 8, the scientists reported findings from their field tests with the tactic at the Solutions to Environmental and Economic Problems (STEEP III) Conservation Farming Conference in Kennewick, Wash.

In the field tests, the ARS scientists measured survival of downy brome seed using five cultivation techniques: no-till, sweep, light harrow, shallow disc and skew-treader.

In years with a dry fall, 13 percent of downy brome seeds survived with the sweep cultivator, compared with 40 percent with no-till. In years with a wet fall, only 3 percent of the seed survived with the sweep versus 9 percent with no-till. Harrowing was largely ineffective. Shallow discing cut seed survival dramatically, but buried much of the soil-protecting residue.

The sweep cultivator also helps reduce soil erosion because the sweep does not invert soil or chop straw left to shield the soil.

Scientific contact: Alex Ogg, USDA-ARS Nonirrigated Agriculture Weed Science Research Unit, Pullman, Wash., phone (509) 335-1551