So I actually called my grandad, whose own grandad owned a rural store that sold a little of everything, from about 1890 something through to a few years after the depression. I asked if they sold fertiliser and pesticides. And the answer was yes, and it ranged from bulk chemicals to proprietary boxed mixtures for specific soil conditions and pests. Everyone used them (even the really, really poor people who had to buy them on credit) because otherwise they weren't getting enough food to survive out of their land. They were comparitively cheap compared to today.
People have been using pesticides and fertilizers for hundreds of years, they weren't invented in 1961.