Biotechnology and U.S. Crop Yields
Ohio State University news
[Professor Zulauf's analysis] does not prove that biotechnology is the reason for the higher yield trend for corn, cotton, and soybeans. It only reveals that the evidence on linear yield trends is not inconsistent with such a conclusion.
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Ohio State University (Dec. 7) -- While not entirely explaining increased yields for corn and soybeans over the past 15 years, one Ohio State University agricultural economist said statistical evidence on linear yield trends shows biotechnology could play a role.
Carl Zulauf, a professor with the Department of Food, Agricultural and Environmental Economics and the Ohio Agricultural Research and Development Center, studied yield trends for corn, soybeans and upland cotton, three crops most widely associated with the adoption of biotechnology. He then compared yield trends for those crops with 11 other crops for which adoption of biotech seed is virtually nonexistent.
"Biotechnology varieties first became available for commercial use in the U.S. in 1996," Zulauf explains. "By 2011, they accounted for 88%, 90% and 94% of the acres planted to corn, upland cotton and soybeans, respectively."
With 15 years of yield data to analyze, Zulauf chose to compare trends from the biotech-influenced era with yield data from years 1940 through 1995, noting that 1940 marked the year when the average yield of most U.S. crops began increasing, due in part to traditional breeding methods.
In evaluating the data, he discovered that only seven of the 14 crops exhibited a higher estimated yield trend during the 1996-2011 period than the comparison years of 1940-1995. The seven crops are barley, corn, cotton, peanuts, rice, soybeans and sugar beets. In other words, of the non-biotech-influenced crops, only four of 11 exhibited a higher yield trend in the more recent of the two data sets.
"This analysis finds that, while the yield trend increased for all three biotech crops after 1996, the yield trend increased for less than half of the crops for which biotech varieties are of limited importance," Zulauf says. "This finding does not prove that biotechnology is the reason for the higher yield trend for corn, cotton and soybeans. It only reveals that the evidence on linear yield trends is not inconsistent with such a conclusion."
He observed that over 10 years, the higher yield trend translated into a harvested yield that was 1.6 bu., 0.6 bu. and 69.1 lbs. higher for corn, soybeans and cotton, respectively. The addition to yield is 1%, 1.4% and 7.9% of the highest harvest yield observed for corn, soybeans and cotton.
"So, for corn and soybeans, the increase in yield trend since 1995 is not large," Zulauf remarks. "The implications, of course, are subject to change with more years of data."
Reduced Yield Variation
In a companion Study (Biotechnology and Variation in Average U.S. YieldsProfessor Zulauf's compared Yield Variability for 1940-1995 vs. 1996-2011 and concludes the decline in yield variability is a universal characteristic of the U.S. crops included in this study. It is not just a characteristic of the biotech crops.
Moreover, little difference appears to exist in the size of the decline in yield variability across biotech and non-biotech crops. While this study cannot preclude biotechnology as an explanation for the decline in yield variability observed for corn, cotton, and soybeans; it suggests more universal factors are likely occurring.
One such factor could be that both biotech and traditional breeding methods have been equally successful at creating varieties that reduce yield variation. A second such factor could be that weather was more favorable across the various U.S. production regions during 1996-2011 than 1940-1995.