Monsanto Co. is paying farmers to increase the number of herbicides they’re using. The rebate program is designed to prevent more acrage from getting infested with weeds that are resistant to one particularly popular herbicide, Roundup.

Monsanto announced today that it’s offering herbicide rebates for the first time for soybeans and increasing rebates for use on cotton fields, where the resistant problem is the worst.

Farmers can earn the rebates for using herbicides other than Roundup, which is the trade name for glyphosate. Roundup is used on most of the soybean, corn and cotton acreage in the country because of the development of biotech seed varieties that are immune to the weedkiller.

However, the overuse of Roundup has led to the spread of glyphosate-resistant weeds, particularly in the South.

Scientists say that farmers need to use a broader array of weedkillers to control the resistance problem and stop relying exclusively on Roundup.

Monsanto is offering soybean growers rebates next year of as much as $6 an acre for the use of two additional weedkillers. The rebates would offset about 25 to 35 percent of the cost of the extra herbicides. Even if farmers use more herbicides next year as Monsanto is trying to get them to do, they likely won’t increase their total weed-control expenses since the price of Roundup has fallen, said Monsanto official Randy Barker.

Most cotton and corn growers already are applying multiple herbicides, but 60% to 70% of soybean growers are using Roundup exclusively, he said. “We’d like to see that jump up to where corn and cotton is at,” he said.

The herbicides that qualify for rebates include Monsanto products such as Warrant as well as chemicals made by competitors.

The use of additional herbicides will not only control Roundup-resistant weeds but add to farmers’ profits by increasing their soybean yields, said Michael Owen, an Iowa State University weed specialist who has been working on a multi-state study on the weed resistance issue funded by Monsanto. 

One recent analysis in Iowa found that weeds early in the growing season could cut soybean yields 6 to 8 bushels per acre, he said. Owen also was a member of a National Research Council panel that warned earlier this year that the environmental benefits of Roundup-resistant crops could be lost if the resistance problem isn’t kept in check.

The use of the herbicide-tolerant crops allows farmers to control weeds without plowing their fields and making the soil vulnerable to erosion.