Now is the time to control weeds in double-crop soybeans.

As planting season approaches, here are a few best management practices for starting clean in fields with winter cereals that will be harvested for forage or cover crops that will be terminated ahead of planting.

Although glyphosate provided superior weed control in the early years, most of the weeds in the dataset showed signs of adaptation to the chemical in just two to three years.

"The use of cover crops in modern Midwest corn-soybeans systems is in its infancy. However, strides are being made to make cover crops an economical part of agriculture."

The study says the data show a rapid falling-off of glyphosate effectiveness against seven major weeds after the first couple of years. The authors conclude that intensive use of any one weedkiller like glyphosate year-after-year serves to speed up evolution in weeds to resist it.

The European Union will extend glyphosate's authorisation for 10 years, even though its member states failed to agree over the active ingredient in Bayer AG's Roundup weedkiller.

Bayer considers separating from its consumer health or crop sciences divisions, according to new CEO Bill Anderson, who is looking to revive the German company’s share price.