Giant ragweed resistant to multiple herbicides is a problem in the Midwest. Researchers in Minnesota studied different crop rotations to see how they affect giant ragweed seeds and emergence. They found that maintaining a zero-weed threshold can deplete the seedbank by 96% in 2 years. Seedling emergence is the main way the seedbank is reduced, especially in corn and soybean rotations. Giant ragweed emerges early, with most plants up by June 4. Rotations with corn and soybean are better for ragweed growth than those with wheat or alfalfa. Alfalfa rotations have slightly longer emergence periods. The study suggests that keeping fields weed-free can help reduce giant ragweed seeds in all crop rotations.