Patterns of GM Soybean Use in Pennsylvania

Genetically modified (GM) crops have had a major impact on U.S. agriculture in recent years and are a hotly debated policy topic. The soybean industry is one that has seen a significant proportion of farmers adopt these new technologies, with nationwide use approaching 70% of the acreage planted in 2001. Especially prevalent are soybean varieties that have been developed to withstand the applic-ation of broad-spectrum herbicides, allowing growers to control existing weeds without suppressing the soybean plants. Use of these varieties also has the potential to reduce tillage, allow a more flexible planting schedule, and increase the use of tactics that control weeds before they’ve begun to sprout.

Soybeans are a major crop in the Midwest, where a shift to the use of GM varieties has been well documented. Although soybeans are not grown on as large a scale in the Northeast, their use has increased in some areas. In Pennsylvania, for example, soy planting rose from 290,000 acres in 1996 to over 400,000 acres in 2002. This increase occurred despite the fact that the price fell by about $2 per bushel over the same period, suggesting that crop yield, costs, and other benefits of this crop in the state’s agricultural systems may have offset the price decreases.

During this time, the use of GM soybeans in the state also increased substantially: USDA data show that GM soy acreage in Pennsylvania shifted from less than 1% of farms in 1996 to just over 70% in 1999. With the use of GM soybeans on the rise, we need to develop a knowledge base that can reveal the economic and environmental implications of this trend.

Dr. Rob Weaver at Penn State is tackling several important questions about the continued expansion of GM soy in Pennsylvania. Using 1996, 1997, and 1999 survey results, Weaver has analyzed data on trends in the use of GM soybeans and has developed empirical models to better understand the pattern of adoption and use of GM soybeans. His work examines the expectations of growers who choose GM soybeans and the characteristics of their operations, and his findings suggest potential impacts on crop yield and implications for chemical use.

When asked about their reasons for making the switch to GM soybeans, 46% of growers indicated that the use of GM seeds would increase yield through improved pest control, and 12% indicated they expected decreased pesticide input expense. Eight percent indicated their adoption of the new technology was based on the increased planting flexibility GM soybeans offer, whereas less than 1% said their decision was based on an expec-tation of improved environmental impacts.

A comparison of growing practices by GM soybean users and non-users (growers of conventional varieties) showed that GM users had simplified their pesticide use strategy and reduced the frequency of ap-plications. In addition, pest scouting was more frequent among GM users. Land use and fertilization practices did not significantly differ between the two groups. Average yield per acre for GM users was 30 bushels, compared to 28 for non-users.

Weaver’s ongoing analysis provides an important picture of current growing practices, and it confirms that Pennsylvania farmers are aware of and use strategies that substitute for pesticides.