Fig. 1. Annual U.S. Corn Grain Yields and Historical Trends Since 1866.
Data derived from annual USDA-NASS Crop Production Reports.
Updated February 2023
URL: http://www.kingcorn.org/news/timeless/YieldTrends.html
Historical Corn Grain Yields in the U.S.
R.L. (Bob) Nielsen
Professor Emeritus
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen at purdue.edu
Twitter: @PurdueCornGuy
- Corn grain yields in the U.S. have steadily increased since the late 1930's.
- Only two major shifts in U.S. corn yield trends have occurred since yield estimates were first published in 1866.
- Year-to-year departures from trend yield are influenced primarily by year-to-year variability in growing conditions.
American farmers grew open-pollinated corn varieties until the rapid adoption of hybrid corn began in the late 1930's. 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. were fairly stagnant and only averaged about 26 bu/ac (1.6 MT/ha) throughout that 70-year period (Fig. 1).
It is amazing to me that there was no appreciable change in productivity over that 70-year time period, even though farmers' seed-saving practices represented a form of plant breeding that one would have expected to result in small increases in yield over 70 years. Kutka (2011) suggests that the absence of significant yield improvement in these open-pollinated varieties was not so much a result of ineffective plant breeding by farmers as it was the inability to produce, or maintain, high quality seed for the next year's planting and farmers' generally low adoption of agronomically sound crop and soil management practices.
Rapid adoption of double-cross hybrid corn by American farmers began in the late 1930's, in the waning years of the U.S. Dust Bowl and Great Depression. Within a very few years after that, the national yield estimates indicated that a genuine "miracle" of corn grain yield improvement had occurred. The annual rate of yield improvement, which heretofore had been about zero, increased to about 0.8 bushels per acre per year from about 1937 through about 1955 (Fig. 1). This dramatic improvement in yield potential must have truly seemed like a miracle to American farmers.
Hybrid Adoption Trivia: An interesting premise put forward by Sutch (2011) is that even though early hybrids had been shown to yield better than open-pollinated varieties prior to the 1930s, "...the drought of 1936 sped the process of adoption after it revealed the drought resistance of hybrid corn." In other words, the yield advantage of hybrids over open-pollinated varieties under severe drought stress was nothing short of "miraculous". The author further states... "After 1937, a new dynamic was set in motion. The explosion of demand for hybrid corn generated large profits for the major hybrid seed companies: Pioneer, Funk, and DeKalb. As a result, the companies invested heavily in research with new hybrid strains. They not only perfected the drought resistance of the plant but also found ways to permit increased planting density, increase the resistance to lodging, and increase responsiveness to artificial fertilizer. The result was a steady improvement in the yields per acre that hybrid corn could achieve. Once these post-1937 improvements were recognized, adoption of hybrid corn became economically advantageous; before 1937, it had not been so."
The second "miracle" of corn grain yield improvement began in the mid-1950's (Fig. 1) in response to continued improvements in genetic yield potential and stress tolerance plus increased adoption of nitrogen fertilizer, chemical pesticides, agricultural mechanization, and overall improved soil and crop management practices. The annual rate of corn yield improvement more than doubled to about 1.9 bushels per acre per year and has continued at that steady annual rate ever since, sustained primarily by continued improvements in genetics and crop production technologies (Fig. 1).
Some speculated that a third "miracle" of corn grain yield improvement would occur with the advent and rapid adoption of transgenic hybrid traits (insect resistance, herbicide resistance) by U.S. corn farmers beginning in the mid-1990's. In fact, a number of seed industry 'experts' confidently promised that average US corn grain yield would approach 300 bushels per acre by 2030 due to these advances in biotechnology (Schill, 2007).
However, the USDA-NASS yield data show little to no evidence that the yield trend over the past 25 years has deviated from the long-term 1.9 bushels per acre per year (Fig. 1). The absence of a marked change in the yield trend line reflects the fact that currently available transgenic hybrid traits do not literally increase genetic yield potential above and beyond "normal" genetic improvements in corn hybrids. Rather, these traits simply protect the inherent yield potential of modern hybrids while potentially reducing farmers' reliance on chemical pesticides. A true third "miracle" of corn yield improvement remains "somewhere over the rainbow".
Trend Line Trivia: Historical trend lines offer a useful way to visualize changes over time. The historical trend yield lines shown in Fig. 1 are technically linear regression lines and represent the best "fit" method for describing the changes in U.S. corn yields over time. The equation associated with the trend line that begins in the 1950s can be used to predict U.S. corn yield for the current cropping year under "normal" growing conditions. Year-to-year departures (changes) from the trend line are caused primarily by year-to-year variability in growing conditions. However, significant changes in the trend line itself (i.e., the slope of the line) are usually caused by significant changes in the adoption of farming technologies (e.g, hybrids, pest control, soil management, mechanization, precision ag. technologies). Irwin and Hubbs (2020) offer an interesting read on how these trend lines are affected by what year you choose to begin the estimation. In particular, one must be cautious when using short time periods because of the greater effects unusual individual years (e.g., drought of 2012) can have on that estimation. My personal preference is to use the time period beginning with 1956, which accounts for 93% of the variability in corn grain yields between then and now (Fig. 1).
Reliance on corn yield trend lines to estimate future corn grain yields is inherently not precise. Annual corn yields fluctuate above and below their respective historical trend lines (Fig. 2), primarily in response to variability in growing conditions year to year (e.g., weather and pests). The "Great Drought" of 2012 certainly resulted in dramatic and historic reductions in corn grain yield relative to trend yield (-22%), but the greatest negative departure from trend yield actually occurred more than 100 years earlier during the "Great Drought" of 1901 (-30%). Conversely, the greatest single positive departure from trend yield occurred in 1906 when the corn crop that year yielded 23% higher than the expected trend yield. The magnitude and range of annual departures from trend yield since the mid-1950's reinforce the evidence from Fig. 1 that the adoption of transgenic hybrid traits beginning in the mid-1990's has not resulted in yields unusually higher than the long-term yield trend.
Bottom Line
The GOOD NEWS is that corn grain yields in the U.S. have steadily increased since the 1950's at almost 2 bushels per acre per year. The SOBERING NEWS is that, in order to support the ever-burgeoning world population in the years to come, a third "miracle" that dramatically shifts the annual rate of corn yield improvement will be required.
Related Reading
Butzen, Steve and Stephen Smith. [unknown date]. Corn Yield Gains Due to Genetic and Management Improvements. Crop Insights, Pioneer, Johnston IA. https://www.pioneer.com/us/agronomy/corn-yield-gains.html [accessed Feb 2023].
Irwin, Scott and Darrel Good. 2012. The Historic Pattern of U.S Corn Yields, Any Implications for 2012? farmdoc daily (2):21, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. https://farmdocdaily.illinois.edu/2012/02/the-historic-pattern-of-us-cor-1.html [accessed Feb 2023]
Irwin, Scott and Todd Hubbs. 2020. How Sensitive Are Trend Yield Projections for U.S. Corn to the Starting Year of the Estimation Period? farmdoc daily (10): 107, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. https://farmdocdaily.illinois.edu/2020/06/how-sensitive-are-trend-yield-projections-for-us-corn-to-the-starting-year-of-the-estimation-period.html [accessed Feb 2023].
Kucharik, Christopher and Navin Ramankutty. 2005. Trends and Variability in U.S. Corn Yields Over the Twentieth Century. Earth Interactions (American Meteorological Society) 9:1-9. https://doi.org/10.1175/EI098.1 [accessed Feb 2023]
Kutka, Frank. 2011. Open-Pollinated vs. Hybrid Maize Cultivars. Sustainability 2011, 3, 1531-1554; doi:10.3390/su3091531. https://www.mdpi.com/2071-1050/3/9/1531/pdf [accessed Feb 2023].
Schill, Susanne Retka. 2007. 300-Bushel Corn is Coming. Ethanol Producer Magazine. BBI International. http://www.ethanolproducer.com/articles/3330/300-bushel-corn-is-coming/ [accessed Feb 2023].
Schnitkey, Gary. 2019. The Geography of High Corn Yields. farmdoc daily (9):2, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. https://farmdocdaily.illinois.edu/2019/01/the-geography-of-high-corn-yields.html [accessed Feb 2023]
Schnitkey, G., C. Zulauf, K. Swanson and N. Paulson. 2021. Recent State Soybean and Corn Yields in Illinois. farmdoc daily (11):68, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. https://farmdocdaily.illinois.edu/2021/04/recent-state-soybean-and-corn-yields-in-illinois.html [accessed Feb 2023].
Schnitkey, G., C. Zulauf, K. Swanson, N. Paulson, J. Coppess and J. Baltz. 2022. Perspectives on National U.S. Corn Yields for Productivity and Down-Side Yield Risk. farmdoc daily (12):103, Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. https://farmdocdaily.illinois.edu/2022/07/perspectives-on-national-u-s-corn-yields-for-productivity-and-down-side-yield-risk.html [accessed Feb 2023].
Sutch, Richard. 2011. The Impact of the 1936 Corn Belt Drought on American Farmers’ Adoption of Hybrid Corn. in "The Economics of Climate Change: Adaptations Past and Present" (Libecap & Steckel, ed.) National Bureau of Economic Research. Univ. Chicago Press. Chapter URL: https://www.nber.org/system/files/chapters/c11987/c11987.pdf [accessed Feb 2023]
USDA-NASS. 2022. Quick Stats. United States Dept. of Agr - Nat'l Ag. Statistics Service, Washington, D.C. URL: https://quickstats.nass.usda.gov [accessed Feb 2023]
Ward, Robert De C. 1901. Some Economic Aspects of the Heat and Drought of July, 1901, in the United States. Bull. Amer. Geog. Soc. 33(4):338-347. DOI: 10.2307/198424. https://www.jstor.org/stable/pdf/198424.pdf [accessed Feb 2023]
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Fig. 2. Annual percent departures from estimated corn trend yields in the U.S. since 1866. Data derived
from annual USDA-NASS Crop Production Reports with respect to historical trend lines depicted in Fig. 1.