What environmental catastrophe in the 1930s brought about substantial changes to farm policy promoting soil conservation?

The environmental catastrophe that significantly influenced farm policy in the 1930s was the Dust Bowl. This severe period of drought, combined with poor agricultural practices, led to extensive soil erosion and the inability of the land to produce crops. As a result, vast areas of farmland, primarily in the Great Plains region, suffered devastating loss, prompting farmers to abandon their land and migrate in search of work and better living conditions.

In response to the crisis, the U.S. government recognized the urgent need for policies focusing on soil conservation and sustainable farming practices. This led to the establishment of various programs aimed at preventing soil erosion, improving crop rotations, and advising farmers on better land management techniques. Initiatives such as the Soil Conservation Service were introduced to implement these policies, marking a significant shift in agricultural practices and government intervention to promote healthier land use and resilience against future environmental challenges.

The other options, while they may represent different issues related to agriculture and the environment, did not have the same immediate and profound impact on farm policy as the Dust Bowl did during that era.