The local farm family has a 100 year legacy of farming this area. It is a dynasty and they till 5000 to 10000 acres depending on leases etc. Judging by the amount of chemicals they use they must own a lot of stock in Monsanto. I watched the field across the road from us. It's about 500 acres. In the fall they planted rye in what had been a soybean field. I thought, "Good, no fall plowing - great for the soil and controls erosion." In late April they sprayed glyphosate (Roundup) on the rye to kill it. Then planted Roundup Ready soybeans, then another application of glyphosate, and now they are over there spraying more chemicals on the beans. It's probably a fungicide mixed with something else, probably another post-emergence herbicide. Whatever it is, it makes the plants look like they are dying for about a week. Last year they had a crop duster plane spraying fungicide a few weeks before harvest.
None of this stuff drifts across the road in quantities that seem to affect our garden, but I'm sure we are getting trace amounts.