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Slowing the Loss of Ag Chemicals

By Don Comis
October 25, 2004

Farmers might be well advised to apply chemicals between crop rows rather than in the rows, according to a study of plowed and no-till cornfields by Agricultural Research Service scientists in Beltsville, Md.

The findings from the two-and-a-half-year study at the agency's Henry A. Wallace Beltsville Agricultural Research Center show that applying chemicals between rows could be safer in terms of reducing the leaching of chemicals to groundwater, especially in areas of the country where rainfall is frequent and no-tillage management is used, such as the mid-Atlantic region.

That's one suggestion to emerge from this first year-round, multiyear study of soil and water dynamics that included charting differences in soil moisture within and between crop rows.

ARS soil scientists James Starr and Dennis Timlin monitored the water content of soil with 16 special probes that recorded soil water every 10 minutes around the clock, at depths of from two to 22 inches. Field weather stations collected data every five minutes. Starr and Timlin studied interactions between the effects of tillage, row position and season of the year on water infiltration, storage, drainage and crop water uptake.

The nearly continuous measurements allowed the researchers to envision how chemicals might move through fields. They compared in-row with between-row water movement during rainstorms, aware that wherever water goes, agrochemicals are likely to go, too.

Starr and Timlin found that the greatest water infiltration occurred within corn rows, especially during summer rainfalls of an inch or more. This was true for no-till, but results were less consistent with plow-till. Aided by the funneling of water to the plants by corn leaves, the soil in corn rows managed to capture a good share of the rain. This large amount of rainwater funneled into the corn rows can then drain through the soil toward groundwater.

A paper on this study has been published in the Vadose Zone Journal.

ARS is the U.S. Department of Agriculture's chief scientific research agency.