- Corn grain yields have steadily increased in the U.S. since the late 1930's.
- Only two major shifts in corn yield trends have occurred since records were first published in 1866.
- Year-to-year departures from trend yield are influenced primarily by year-to-year variability in growing conditions.
Historical grain yields provide us with a glimpse of yields yet to come, although like the stock markets, past performance is no guarantee of the future. The historical yield data for corn in the U.S. illustrate the positive impact of improved crop genetics and crop production technologies.
From 1866, the first year USDA began to publish corn yield estimates, through about 1936, yields of open-pollinated corn varieties in the U.S. remained fairly stagnant and averaged about 26 bu/ac (1.6 MT/ha) throughout that 70-year period. Amazingly, the historical data indicate there was no appreciable change in productivity during that entire time period (Fig. 1), even though farmers' seed-saving practices represented a form of plant breeding.
Rapid adoption of double-cross hybrid corn by American growers began in the late 1930's, in the waning years of the Dust Bowl and Great Depression. Within a very few years, the yield data indicated that a significant improvement in corn productivity had occurred, that resulted in an annual rate of yield improvement of about 0.8 bu/ac/year from about 1937 through about 1955 (Fig. 1).
A second significant improvement in the annual rate of yield gain began in the mid-1950's in response to continued improvement in crop genetics, increasing adoption of N fertilizer and chemical pesticides, and agricultural mechanization (Fig. 1). Since 1955, corn grain yields in the U.S. have increased at a fairly constant 1.9 bushels per acre per year, sustained primarily by continued improvements in genetics and crop production technologies (Fig. 1).
Some speculate that a third significant improvement in the annual rate of yield gain is "on the horizon", in part due to the advent and adoption of transgenic hybrid traits beginning in the mid-1990's. However, the USDA-NASS yield data show little evidence that the yield trend has deviated since the last big shift beginning in the mid-1950's (Fig. 1).
Annual yield estimates fluctuate above and below the yield trend line over the years (Fig. 2). The annual departure from yield is primarily in response to variability in growing conditions year to year (weather, pests). The Great Drought of 2012 certainly resulted in dramatic and historic reductions in corn grain yield relative to trend lines, but the greatest negative departure from trend yield actually occurred more than 100 years earlier during the Great Drought of 1901. The annual departures from trend yield since the mid-1950's reinforce the evidence from Fig. 1 that the advent and adoption of transgenic hybrid traits beginning in the mid-1990's has not resulted in noticeably greater departures from trend yield.
So, the good news is that corn grain yields in the U.S. have steadily increased since the 1950's. The sobering news is that, in order to support the ever-burgeoning world population in the years to come, a third and MAJOR shift in the annual rate of yield gain will be required.