Can farmers play hardball with weeds in cotton, corn and soybeans, using an expensive brew of herbicides that include glyphosate, manage resistance problems, and come out ahead on the bottom line?

A six-state, multi-year study indicates in North Carolina they can. Other states included in the test showed similar results.

In North Carolina, cooperating farmers were asked to split their test fields in half. In one half they managed weeds as they do normally — the farmer approach. In the other half they managed weeds based strictly on university recommendations — the university approach.

North Carolina State University researchers looked at continuous soybean fields, continuous cotton fields and soybean and corn rotations in the study.

The university approach included additional preplant, pre-emergence or postemergence herbicides. These herbicides included a wider range of modes of action and active ingredients than a typical farmer herbicide program. Both farmer and university herbicide programs included glyphosate in the herbicide mix.

With the increase in acreage of glyphosate resistance in cotton and corn, primarily by Palmer amaranth, the need for a more comprehensive weed management program seems essential. Too many farmers haven’t taken the extra time and spent the extra dollars to manage weed resistance in the past few years, making the North Carolina portion of the study extremely poignant.

The bottom line for both types of herbicide programs was calculated using the same North Carolina State University enterprise budget. Profitability of cotton was based on 60 cent, 80 cent and $1 per pound of lint. For corn $3, $5, and $7 dollars per bushel were used and for soybeans $8, $12, and $16 dollars per bushel were used.

For conventional planting per acre costs, minus herbicide costs, were set at $371.85 for corn, $497.51 for cotton and $218.54 for soybeans. For reduced-tillage systems these per acre costs were $346.63 for corn, $474.47 for cotton and $188.21 for soybeans.

Agronomist David Jordan, who helped coordinate the North Carolina State portion of the six-state study says the more intensive and diverse use of herbicides paid off in both continuous cotton and soybeans.

“In cotton, the economic benefit of using the more intense university approach probably came from reduction in early season weed interference with cotton. We didn’t see much difference in weed populations later in the season, indicating the affect came early rather than late,” Jordan says.