ERS Study Shows Differences In Gene-Altered Crop Results

July 26,1999

A new study from USDA's Economic Research Service shows increases in adopting herbicide-tolerance cotton are associated with significant increases in yields and variable profits but were not associated with significant changes in herbicide use. Using herbicide-tolerant soybeans helped fuel small yield and variable profit increases and significant declines in herbicide use.

The study notes that benefits to farmers and the environment from adopting genetically engineered crops are difficult to assess. "Attributing differences in yields, pesticide use and profits between adopters and nonadopters observed in the data solely to adoption of genetically engineered crops is nearly impossible, because many other factors also affect yield and pesticide use."

Larger operations and more educated operators more likely will use herbicide-tolerant soybean seed, the study found. Expected profitability "positively influences the adoption of agricultural innovations." Use of conventional tillage is another significant factor that reduces adoption, since farmers use conventional tillage to help control weeks, while herbicides are used with conservation or no-till practices.

Cotton production relies heavily on herbicides to control weeds, often requiring applications of two or more herbicides at planting and post-emergence herbicides later in the season. In 1997, increases in adoption of herbicide-tolerant cotton are estimated to have increased yields, leading to increased variable profits. But no statistically significant change in herbicide use on cotton was observed in 1997, the study says.

However the increased use of herbicide-tolerant soybeans produced only a small increase in yield and no significant change in variable profits in 1997. Almost two-thirds of the herbicides used on soybeans were synthetic materials other than genetically engineered products that produce a tolerance to glyphosate herbicide in soybeans. As GMO adoption increased, use of glyphosate herbicide (such as Roundup) also increased, but the use of other synthetic herbicides declined by a larger amount. The net result was a decline in the overall pounds of herbicides applied.