World War II not only changed how food was packaged and consumed but also how it was grown. Farmers found new uses for chemicals deployed in World War II, as nitrate factories quickly shifted from making bombs to making fertilizer.
Nitrogen fertilizer - along with phosphorus and potassium fertilizers - suddenly became cheaper and more available. Around the same time, hybrid varieties of corn, wheat, and soy were widely adopted and required large amounts of fertilizer to reach their promised high yields.
Similarly, the use of synthetic pesticides became the main form of pest management after the war. Pesticides like dichlorodiphenyltrichloroethane (DDT) had been used in the war to prevent insect-borne diseases like malaria and typhus. Now farmers discovered they were also cheap and effective for controlling crop pests.
The rise of synthetic fertilizer and pesticide use is credited with increasing crop yields, decreasing pressure on farmers to farm more land, and lowering food prices. But their risks to our environment and our health was not commonly known. In fact, DDT was seen as a low-toxicity chemical, not a probable cancer-causing agent. It was viewed as a safer option than the arsenic-based pesticides that came before it.
However, regulations began to target the use of DDT in the 1950s-1960s as concerns grew about its safety. Air and water pollution from the production and use of fertilizer and pesticides was becoming difficult to ignore.