In recent years, some no-tillers have criticized strip-till, pointing to instances of severe soil erosion in fields that were strip-tilled up and down hills.

But more than 25 years ago, a study by three agricultural engineers at the University of Illinois showed that strip-tilling on the contour effectively minimized soil erosion and limited losses of herbicides and insecticides.

Here’s a summary of that research, published in the American Society of Agronomy’s Journal of Environmental Quality. The full text of the article, “Assessment of Management Practices for Reducing Pesticide Runoff from Sloping Cropland in Illinois,” describing the research, is available for a fee on the ASA’s Web site.

Ag engineers Allan Felsott, J. Kent Mitchell and Ann L. Kenimer studied the impact of tillage systems and contouring on the runoff of soil-applied pesticides using rainfall simulators in small plots. They planted plots to corn in 1983 and 1985 and soybeans in 1984.

“Runoff was measured during a 60-minute event with a rainfall intensity of 63 mm (2.5 inches) per hour,” according to the ag engineers. “During 1984, moldboard-plowed and no-till systems were studied with rows oriented on the contour or up-and-down the slope (7% to 11% slope). Compared to moldboard plow, up-and-down slope no-till and contouring significantly reduced runoff of carbofuran and alachlor.”

The percentage of applied carbofuran lost in runoff and sediment ranged from 1% (contoured moldboard) to 11% (up-and-down the slope moldboard).

The researchers reported that the percentage of applied alachlor lost ranged from 1% (contoured no-till) to 2% (contoured moldboard).

In 1985, they studied the effects of row orientation in strip-till, no-till, moldboard-plow, chisel-plow and ridge-till.

Under up-and-down slope conditions, strip-tilling cut the runoff of alachlor and terbufos plus two metabolites (terbufos sulfoxide and terbufos sulfone) to a less of less than 1% vs. a loss of 6% in moldboard plowing.

 “Larger losses of alachlor (2% of applied) from up-and-down slope no-till than from the other conservation tillage systems (1% or less) was attributed to high concentrations in runoff associated with extensive washoff of the herbicide from soybean crop residues,” the engineers said.

With contouring, strip-till held losses of applied pesticides to less than 0.1%, while ridge-till kept pesticide runoff to less than 1% of application.

“Although, no conservation tillage system completely eliminated pesticide runoff, losses were most effectively minimized by contoured strip-till and no-till, which controlled both water and sediment movement,” the researchers said.