Which crop is an example of increased southern farming variety beginning in the 1970's

Soybeans

Explanation:

Soy beans is an example of increased farming variety beginning in the 1970s. The 1970s period has been characterized broadly as a period of great farm prosperity, this is likely caused by a short period of high farm income.

In the early 1970s, soybean sales grew more than corn, this caused it to become America's number one cash crop.