Two years of NU Institute of Agriculture and Natural Resources research showed Roundup Ready soybeans yield 6 percent less than their closest relatives and 11 percent less than high-yielding conventional soybeans. This averages to three fewer bushel per acre, or 480 fewer bushels on a 160-acre field. NU Agronomist Roger Elmore, who headed this study, said the research was initiated after producers began asking yield-related questions about Roundup Ready soybeans in 1997, about the same time early test results from Nebraska and other state universities were released. The questions and early results hinted Roundup Ready soybeans yielded less than conventional beans. Soybeans are broadleaf legumes that grow to about 30 inches, leaving them susceptible to weeds such as velvetleaf, waterhemp and shattercane.
Weeds can outgrow soybeans, stealing moisture, sunlight and nutrients, and thus lower yields.
Weed management can be tricky because most broadleaf herbicides can wipe out soybeans, along with weeds. Roundup Ready soybeans contain a gene that allows them to be treated with Roundup Ultra, the most popular of the glyphosate-based herbicides. Their studies showed spraying had no effect. Roundup Ready yields were consistently 55 bushels per acre, which indicated Roundup didn't affect soybean growth, development or yields. From that, the scientists deduced the gene insertion process was responsible.