After World War II farmers transformed the Iowa landscape by using newly developed growth regulator herbicides while simultaneously shaping the way herbicides were used. Herbicides met many farmers' goals, including cutting fuel and labor costs of cultivating while boosting yields by reducing weed competition for soil nutrients, light, and moisture. In the 1940s and 1950s, experts advised farmers to only use chemicals to supplement mechanical cultivation, but by the 1960s some farmers reduced or eliminated cultivation. Farmers also contended with unanticipated consequences of herbicide use. Some weeds were resistant to herbicide and proliferated as farmers reduced or eliminated species that were easier to control. Weed control became more expensive and complicated by 1972, with new varieties, combinations, additives, and government regulation. In spite of the expense of herbicides and some undesirable consequences, farmers continued to use them, accepting a new chemical paradigm and altering the Midwestern landscape.