Peanut allergies have plummeted in children

Have there been any studies on crop-swapping changes such as legumes <--> cotton? Only asking as there were some theories about excess herbicides and pesticides from cotton leeching into the ground and getting absorbed in high amounts by legumes from seasonal crop-swaps.

I'd like to see that, as the current studies seem too convenient. Or at the very least, compare peanut butter from 2005 to peanut butter from 2025.