By James Barnett
CHICAGO (B)--Throughout the U.S. soybean harvest, there have been widespread reports of disappointing yields due to a host of factors, ranging from late season dryness in parts of the western Corn Belt to a high incidence of disease in parts of Illinois and Indiana. Now, analysts and agronomists say they will be watching for a possible drop in yields on fields planted with Roundup Ready soybeans.
"During certain conditions, there is a yield penalty in side-by-side comparisons for soybeans with the Roundup Ready gene," said Jim Quinton, analyst with Crop Information Assoc. in Carlinville, IL.
"Specifically, Roundup Ready soybeans tend to lag in years with difficult planting or a difficult harvest."
Quinton noted Roundup Ready soybeans were very popular on the southern edge of the soybean belt where planting was delayed this year and where they tend to plant late-maturing varieties.
"Southern Illinois, southern Indiana, western Kentucky and southern Missouri are strong Roundup Ready neighborhoods," said Quinton. "The farmers in a lot of these areas are just getting around to harvesting." Quinton mentioned Perry County in Missouri, Jackson County in Illinois and Gibson County in Indiana as areas to watch to see if yields are impacted on Roundup fields this year.
"We could have five to 10% yield declines on Roundup fields in some areas," he said. "All I can tell you right now are patterns and not statistics, and so we need to wait for the actual results."
Ellsworth Christmas, soybean extension specialist at Purdue University in West Lafayette, IN, said that, over the past three years, production for Roundup Ready soybeans were about five% lower than for non-Roundup fields in performance trials conducted across several north-central states.
"We still have to look at performance data for this year," he added. However, it is far from certain that Roundup Ready soybeans have lower yields in this or any other year.
Bryan Hurley, a spokesman for Monsanto, said in 1999 a side-by-side comparison conducted for Monsanto by PSL Genetics under "normal conditions" on 25 locations in Indiana, Illinois and Ohio found an average yield of 53.2 bushels per acre for Roundup Ready soybeans, compared with a yield of 52.9 bushels for conventional soybeans.
"Statistically, the study found there was no significant difference between Roundup Ready soybeans and other varieties," he said.
Agronomists said the issue bears watching.
"When you develop resistance in a new hybrid, whether to disease or, in this case, a chemical application, you tend to get either a yield drag or a yield lag," noted Christmas.
A yield drag is a lower yield associated with the genetic characteristics that enable the resistance. In addition, while the hybrid is being developed, other varieties chosen for higher yields enter the marketplace, and resistant hybrids tend to have a yield drag compared to these newer, high-yielding varieties.
Quinton observed, "Roundup does not have a zero effect on Roundup Ready soybeans. It still can stunt the plant a little, particularly in a year where conditions are already poor."
Christmas noted he has heard many anecdotes from farmers, but added, "Low yields on a particular field do not necessarily correlate to seed variety."
Roundup is a glyphosate-based herbicide which kills a wide variety of weeds in a field, eliminating the need to apply a series of separate herbicides for different types of weeds. Roundup Ready is a genetically modified type of soybean seed designed to be resistant to the effects of the Roundup herbicide.
"Roundup Ready soybeans have an easier management program, which is one of the reasons farmers like them so well," said Christmas.
Hurley estimated that this year around 60% of the U.S. crop was a variety of Roundup Ready soybeans and that Monsanto has approved or licensed roughly 1,000 varieties of Roundup Ready seeds.