Sorting Seeds, Saving Water

Agricultural Research Service (ARS) scientists are wielding a new weapon in the war on weeds. It isn't meant for direct action, though, but instead to gather valuable information on underground stores of weed seeds, dubbed "seed banks," that enable some species to re-infest fields for years to come.

The elutriator, as the weapon is known, uses high-powered jets of water to blast seeds from soil-core samples taken 10 to 30 centimeters below the surface of crop fields. Scientists then collect the seeds to determine their species, number, health and ability to germinate.

Until a few years ago, such seed sorting was done by hand over a sink with the faucet running, according to Adam Davis, an ecologist with the ARS Invasive Weed Management Research Unit at Urbana, Ill. Now that tedious and time-consuming process is carried out with high efficiency by the elutriator, which can handle 48 soil-core samples. It blasts the seed with water at the rate of nearly six gallons a minute, or 360 gallons per hour.

Despite the advantage, Davis and colleagues were concerned about the water they were using to aid their weed-seed research. James Moody, an ARS biological science technician at Urbana, studied the machine and proposed some modifications. These included hooking up a submersible pump to the elutriator's settling tank and installing a water meter and flow-limiting valve in the water line.

In trial runs and actual research, Moody's modifications consistently reduced the elutriator's water used by 13 percent, or 50 gallons, per hour, mainly by recycling the water. Further tweaking of the machine could reduce water use by 50 percent, according to Davis.

Of particular interest to Davis and colleagues is developing sustainable methods of weed control. These will include encouraging greater predation of weed seeds by birds, rodents, insects, and even bacteria in the soil.

Read more about this research in the February 2009 issue of Agricultural Research magazine.

ARS is a scientific research agency of the U.S. Department of Agriculture.