In the late 1990s clean beans came to Iowa.
The beans had a resistance to a broad spectrum herbicide.
Farmers have used herbicides against the weeds for over half a century, but never with the complete success that the herbicide resistant beans had. Prior to this, they had to use a narrow spectrum herbicide—one that would kill monocots but not dicots. Or they would kill all the weeds prior to planting. Or they would go through with a bar and a rope wick, saturated with roundup, which would kill all of the weeds that were taller than the soybeans. Still, they had to mechanically cultivate or hire high school kids to walk the fields and pull out the weeds.
With the new tools, there was a noticeable difference in the fields. The areas between the rows were absolutely bare of live vegetation. Even the non-farmers like me noticed the difference.