To put farm modernization in a nutshell, a modern plow attached to a tractor can do the work of a dozen plows pulled by cattle. Instead of milking one cow at a time, milking machines can be wired to deliver milk from multiple cows to the tank. With farm modernization, it's not that farming has become a lost art entirely; it's just that so much work can be done today by just a few.
Corn and soybean comprise the majority of U.S. crop production. More than 9 million acres of corn yielded over 14.2 million tons, while roughly 8.4 million acres of soybean yielded close to 4 million tons in 2014. At the turn of the 20th century, corn production was only a bit over 2 million tons.
Modern equipment also drove prices down, from $0.49 per bushel in 1870 to $0.36 in 1900 in corn. Although corn prices in 2014 clocked in at $3.77 per bushel, the prices aren't adjusted for inflation yet. The relative values of corn per bushel back then, at the bare minimum, would be $8.12 and $5.97, respectively.