The technological changes that took place in agriculture during the 20th century have caused some major shifts in crops grown on farms. Among the most dramatic of these changes is the decline of land devoted to oat production and rise in soybean acreage.

Oats were a major crop dating from colonial days because of their importance as a livestock feed grain, particularly for horses and mules. Harvested area peaked at 45.5 million acres in 1921 (coincidentally, the first processing of domestic soybeans occurred about this time in the Corn Belt) and continued in the 35 to 40 million-acre range until 1955. Since then, harvested acreage has declined rapidly to less than 3 million acres. The decline in acreage was not as precipitous as that of horses and mules because of the continued use of oats as feed for other livestock and for human consumption.

Soybean acreage for beans climbed slowly, from less than a half million acres in the early 1920's to over 1 million by 1930. The upward trend continued, doubling every 6 or 7 years until 20 million acres were cultivated in 1956. This was the first year that the acreage of soybeans produced for beans exceeded 95 percent of planted acres. The rate of expansion then slowed somewhat, requiring more than 12 years to double again. Acreage for beans has generally totaled between 55 and 65 million since 1977.

The early popularity of soybeans was due to their nitrogen-fixing properties and conservation uses. Increasing use of the soybean’s oil and crush by-products later in the century ensured its importance as a cash crop for many years to come. By the close of the century, over 70 million acres of soybeans were planted.