by Dr. Charles Benbrook
For those unfamiliar with the basics of soybean herbicides and the impacts of GMO/RR (Roundup Ready) soybeans on use rates, the simple facts are these.
In the early to mid-1980s, most soybean herbicides were applied in combinations, and at a combined rate between 0.75 to 1.5 pounds per acre. These are sometimes today called the “traditional” soybean herbicides or weed management systems (see below).
By the mid- to late 1980s and throughout the 1990s, the pesticide industry developed and marketed dozens of new, low-dose soybean herbicides in the imidazolinone and sulfonylurea classes. These products are applied typically in the 0.05 pounds active ingredient per acre to 0.2 pounds per acre range. Often, two active ingredients are required, resulting in total per acre application rates of 0.1 to 0.3 pounds per acre.
To this day, some acres are still treated with the old conventional herbicides applied at rates between 1.0 and 2.0 pounds per acre, again mostly in combinations. In recent years about 15% of acres are treated with trifluralin at about .9 pounds/acre and another 16% or so with pendimethalin at .97 pounds per acre. These products are typically supplemented with an application of another herbicide, and in some cases are used prior to planting RR beans.
Along comes RR beans in 1996. Adoption has increased to over 55% of acres, at an average rate of application of about .92 pounds of glyphosate per acre per season (average about 1.3 applications per acre; i.e. about one-third of growers use 2 applications). Roundup is typically used in combination with other products, bringing average total herbicide use per acre to about 1.5 pounds (see our forthcoming report for source of these data). Many farmers using RR beans are applying over 2 pounds per acre, a few apply less than 1 pound.
So, if you are a biotech proponent or Monsanto, you compare herbicide pounds applied at the low-end of the Roundup Ready treated acres distribution, i.e. at a rate of about 1 pound per year, to the small percent of acres treated just with the higher-dose, older products. Monsanto has prepared a document called “Chemical Reduction Benefits of Biotechnology Crops, Compiled November 30, 1999.” This document is for the press, political leaders, and PR purposes and has been widely disseminated. On the Roundup herbicide use and GMO-soybean front, it states —
“In a Sparks Commodities, Inc. study conducted in 1996 and 1997, in-season herbicide use in Roundup Ready soybean fields was shown to be less than TRADITIONAL SOYBEAN FIELDS by an average of 26 percent and 22 percent respectively, over four regions of the United States.”
This statement is probably true in a narrow sense but is also creatively misleading if not down-right dishonest. What the statement means is that there are soybean producers in each of four regions still using the older, higher-rate herbicides, and compared to their weed management systems, the “traditional soybean fields,” herbicide use in RR bean fields is less.
What the Monsanto materials do not say is that if the comparison was instead to the average soybean field not planted to RR beans, or even worse, to farmers using “modern, low-dose herbicides,” the results would be very different. In my review of the RR yield drag (accessible Here), I stated that Roundup use is between 2 and 5 times greater measured on the basis of pounds applied per acre, when the comparison is between the average field planted to RR beans and most other soybean acres not planted to GMO varieties. When compared to systems utilizing the really low-dose herbicides, the Roundup ready fields require more than 10 times the herbicide, but such a selective comparison would be analytically dishonest. But I guess it all depends on what you feel the rules are and whether everyone has to follow them.
Soon we will release a new report that very clearly shows that on the average RR soybean fields, substantially more herbicide is applied when measured on the basis of total pounds of active ingredient applied per acre compared to the average non-GMO soybean fields. When a truly fair comparison is made of average rates, the answer is clear.
There are many benefits to farmers of the RR soybean technology despite the yield drag (recently confirmed by researchers at Nebraska), greater reliance/use of herbicides, and the system’s higher cost (compared to some alternatives). But reducing herbicide use is not one of them.
(The Nelsons are a family of farmers in North Dakota, being sued by the St. Louis based, Biotechnology giant, Monsanto. You can visit their site at NelsonFarm.net)