Improvements in technology, animal husbandry, and cropping practices all contributed to dramatic increases in agricultural production during the 20th century. Corn has been and continues to be produced on more area than any other U.S. crop, with corn acreage peaking in 1917 as technological factors began to make it possible to produce more on less land.
Yield
per acre of corn for grain used for livestock feed provides a prime example
of this production boom. One factor related to increases in corn yields
was the introduction of double-cross hybrid seed varieties in the early
1930's. These hybrid varieties led to improved yields by increasing the
plant’s resistance to pests and diseases. They were also more adaptable
to variable growing conditions and often aided the harvesting process. In
1935 only 1 percent of the corn crop was seeded with hybrids, but by 1940
the total was more than 30 percent. 
Hybrid
seed accounted for 96 percent of the corn acreage by 1960.
Corn yields continued to rise toward the end of the century, although with a higher degree of variability. This variability indicates that there are other factors that have an impact on yields, such as the weather, irrigation practices, or use of nitrogen fertilizer.
The development of hybrid seed was not limited to corn. Wheat is another example of a crop for which hybrid seed was developed to improve the characteristics of the plant and raise yields.
