In soybeans, the university approach resulted in fewer weeds later in the year, indicating the economic benefit at low, medium and high crop values, probably came from more of a season-long affect of reduced weed competition, Jordan explains.

In both cotton and soybeans, the more intensive university approach typically produced around 10 percent higher yield than the less expensive, but less efficient farmer approach.

In the corn and soybean rotation the researchers found fewer differences across all parameters of the study, except herbicide price and diversity of activity on weeds.

“Although it was covered in this study, it is clear that good crop rotation is valuable in producing an overall healthier crop that is better able to compete with weeds, regardless of herbicide or crop mix,” Jordan says.

In general, weed populations were higher at the end of the season in continuous soybeans than in corn-soybean rotations. Weed densities in cotton were generally lower than either continuous soybean of corn-soybean rotations.

In 2011, cotton, soybean and corn seed are all going to be expensive and in some cases in short supply in some of the more desirable varieties. The 10 percent more yield at a dollar per pound for cotton and comparable high value of beans and corn will make the extra 10 bushel per acre yield more valuable than the extra cost of an intensive herbicide program.

In continuous cotton, the extra herbicide cost in the university program was $22 per acre. Even in cotton at 2008 prices, getting 100 pounds more per acre would nearly double the extra cost for herbicides used in the university approach. Clearly, at $1 per pound, the benefit would be significant.

In continuous soybeans, at the current (mid-February) price of soybeans, the advantage for the university approach to weed management would be nearly 2 to 1 in dollars spent versus dollars gained.

Some growers look at the extra cost associated with using multiple modes of action and different application times as insurance against weed resistance. In reality, this study shows more intensive weed management pays in both the short-run and the long-term.

The cost advantage is very clear, Jordan points out, on continuous soybeans or cotton. Though there is no significant cost advantage on soybean and corn rotations, there is a significant long-term advantage of keeping fields clean and free of herbicide resistant weeds that can become a big problem in a short period of time.

As growers get ready to plant some very expensive cotton and soybean seed this year, spending the extra dollars in weed management is likely to pay off better than ever before.

rroberson@farmpress.com