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Wheat Yield Analysis in Relation to Advancing Technology in the Midwest United States

Dep. of Statistics and Statistical Lab.

G. M. Paul

Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506.

^* Corresponding author.

Improving grain yields requires knowledge of sources of gains in the past to point the way to future advances. Our objectives were to analyze technology-related yield changes of winter wheat (Triticum aestivum L.) in the US. Great Plains (a seven-state region) and the Cornbelt (a four-state region) since 1954 and to attribute them to major sources of variation. Within each of the 11 states, total yield change due to technology, yield change due to genetic improvement, and yield change due to applied N, were independently estimated. Yield change due to other factors was obtained by subtracting genetic and applied N induced changes from the total. Results were aggregated to regional levels. Wheat yields advanced 30 kg ha^–1 yr^–1 in the Great Plains and 43 kg ha^–1 p^–1 in the Cornbelt from 1954 through 1979. In the Great Plains, 43,22, and 35% of the total increase was attributed to genetic improvement, applied N, and other sources, respectively. Comparable figures for the Cornbelt were 74, 22, and 2%. When the analysis was extended to 1984 for Nebraska, Kansas, and Oklahoma, the rate of increase remained almost the same, but the distribution among genetics, N, and other sources changed from 45, 25, and 30% for 1954 through 1979, to 61, 27, and 13% for 1954 through 1984. We concluded that from 1954 through 1979, genetics and applied N accounted for almost all the yield gain in the Cornbelt, but other factors (irrigation, pesticides, improved tillage, etc.) contributed about one-third of the gain in the Great Plains. Technology continued to raise yields at the same rate in the central Great Plains during the 1980s, but a larger share was due to genetic improvement than during 1954 through 1979.

Received for publication October 5, 1987.