Does GE Increase Yield?

 Does GE Increase Yield or Profits to Farmers?

Cliff Kinzel produced the following collation on yields of GM crops. This does not bear out the PR promises of higher yields and greater profits for farmers. 

1998, April The Cotton Grower – A. Sutton 

For Contact: 

Arkansas Research Shows: Plant Bt Cotton Strategically 

FINDINGS: One of Bt cotton's selling points has been reduced inputs for growers, hence higher returns per acre, but in seven observations in three Arkansas counties in 1997, net income decreased by $25 per acre. The research, conducted by the University of Arkansas, was designed to determine changes in net income per acre of the Bt fields versus non-Bt fields. The Bollgard varieties did not yield as well as the non-Bt varieties. Growers are concerned about the low yield potential of Bollgard cotton. Farmers need all the yield they can get in order show a profit. ________________________________________________________________________________ 


Evidence of the magnitude and consequences of the Roundup Ready Soybean yield drag from university-based varietal trials in1998. – C. Benbrook 

FINDINGS: Report reviewed the results of over 8,200 university-based soybean varietal trials in 1998 and reached the following conclusions regarding the magnitude of the RR soybean yield drag.

* The yield drag between top RR varieties compared to top conventional varieties averaged 4.6 bushels per acre, or 6.7 percent. 

* When comparing average yields across the top 5 varieties tested in 8 states, the yield drag averaged 4.1 bushels, or 6.1 percent.

* Across all varieties tested, the yield drag averaged 3.1 bushels, or 5.3 percent. 

* In some areas of the Midwest, the best conventional variety sold by seed companies produced yields on average 10 percent or more higher than comparable Roundup Ready varieties sold by the same seed companies.

On whether RR soybean systems reduce pesticide use and increase grower profits, the analysis showed that: 

* RR soybean systems were largely dependent on herbicides and hence were not likely to reduce herbicide use or reliance. Claims otherwise were based on incomplete information or analytically flawed comparisons that did not tell the whole story.

* Farmers growing RR soybeans used 2 to 5 times more herbicide measured in pounds applied per acre, compared to the other popular weed management systems used on most soybean fields not planted to RR varieties in 1998. RR herbicide use exceeded the level on many farms using multitactic Integrated Weed Management systems by a factor of 10 or more. 

* There was clear evidence that Roundup used by farmers planting RR soybeans had risen markedly in 1999 because of the emergence of a degree of tolerance to Roundup in several key weed species, shifts in weeds toward those less sensitive to Roundup, price cuts and aggressive marketing. 

* Roundup use on soybeans may well double from 1998 levels within the next few years. But if current trends continued in the way RR technology is used, the efficacy and market share of Roundup may then fall just as quickly. 

* The RR soybean yield drag and technology fee imposed a sizable indirect tax on the income of soybean producers, ranging from a few percent where RR varieties work best to over 12 percent of gross income per acre. 

The remarkable popularity of Roundup Ready soybeans, despite their cost and the significant yield drag associated with their use, was evidence of the difficulty and high cost of today's herbicide-dependent soybean weed management systems. The rapid evolution of weeds better able to withstand applications of Roundup reinforces the need for more integrated, multiple tactic weed management systems. ________________________________________________________________________________ 

1999, Fall Leopold Letter Vol. 11 No. 3 

Does planting GMO seed boost farmers' profits? 

FINDINGS: Information was gathered in the late fall and early winter of 1998 during personal interviews with approximately 800 Iowa farmers and only represents a picture of what Iowa farmers experienced, under varying conditions and situations, during the 1998 crop year.

Farmers who did not use GMO varieties in 1998 reported a slightly higher yield than those who used GMO varieties. 

The average yield for non-GMO soybeans was 51.21 bushels per acre; the average yield for GMO soybeans was 49.26. 

Farmers who used GMO varieties experienced significant savings in herbicide costs, spending nearly 30 percent less than farmers who grew non-GMO soybeans. 

Farmers using GMOs held a cost advantage in all aspects of weed management. 

Farmers who planted GMO varieties reported an average seed cost of $26.42 per acre, compared to $18.89 per acre for non-GMO varieties. 

Total costs without land or labor were $115.11 for GMO soybeans, and $124.11 for the non-GMO soybeans. Returns to land and labor were essentially identical for GMO and non-GMO soybeans. 

GMO soybeans had a return of $144.50 per acre versus a return of $145.75 for non-GMO soybeans. Results from these 365 soybean fields indicate that 1998 yields from GMO soybeans were slightly lower than conventional varieties, but so were the costs. 

According to this analysis, Iowa farmers had identical returns in 1998, whether they raised GMO or non-GMO soybeans. 

In 1998, the average yield for Bt corn was 160.4 bushels per acre. The average yield for non-Bt corn was 147.7 bushels per acre. Farmers applied insecticides on 12 percent of their Bt corn fields at an average cost of $17.56 per acre. They applied insecticides on 18 percent of their non-Bt corn fields at an average cost of $14.94 per acre.

The biggest cost difference between Bt and non-Bt corn was in seed. Seed for Bt corn averaged $39.62 per acre, compared to $29.96 per acre for non-Bt corn. Bt fields had slightly higher weed control costs, averaging $2.82 per acre. Fertilizer costs were $5.02 per acre higher than non-Bt corn. 

When comparing gross revenue, total costs, and the return to land and labor between Bt and non-Bt corn, corn was valued at the 1998 average price of $1.90 per bushel. The total difference in return to land and labor was only $3.97 per acre. 

Conclusions Based on a cross-sectional examination of Iowa cropping practices in 1998, genetically-modified crops provided farmers with no significant difference in returns. Remember, this is not a comparison of genetically-modified crops with their conventional counterparts, but a look at the bottom line last year for Iowa farmers – so were costs. 

In corn, yields and costs were higher when GMO seed was used. Based on what happened in 1998, Iowa farmers will find returns per acre relatively unaffected whether or not they plant the GMO corn and soybeans currently available. ________________________________________________________________________________ 

1999, January 14 The Montreal Gazette – Montreal, Québec, Canada 

Agriculture Canada Study questions higher-yield theory on genetically modified canola.

FINDINGS: Farmers won't necessarily get higher yields by growing costly genetically modified canola, a new Agriculture Canada study suggests. The two-year study indicated herbicide-tolerant canola brought bigger yields than traditional farming methods in only 60 per cent of test fields.

Those results should prod Prairie canola farmers to be more prudent when deciding which farming method to use, said Bob Blackshaw, an Alberta weed specialist who conducted the study 

"There is this general assumption by farmers that they get higher yields and make more money if they used herbicide-tolerant canolas," Blackshaw said. "They might get better economic return on their farm by not growing a herbicide-tolerant canola." ________________________________________________________________________________ 

1999, November 11 University of Missouri 

MU Tests Find Comparable Yields Between Bt, Non-Bt Corn Hybrids.- F. Rose 

FINDINGS: Bt, or non-Bt? That is the question. 

University of Missouri researchers sought the answer this year with greatly expanded variety tests of Bt and non-Bt corn hybrids at 15 different sites across the state. Their preliminary conclusions are that Bt hybrids yield comparably to non-Bt hybrids, but lack of pressure from the European corn borer made Bt hybrids less profitable in Missouri this year. ________________________________________________________________________________ 

2000, May 17 The Associated Press State & Local Wire 

Study shows genetically altered soybeans produce lower yields. 

FINDINGS: A two-year study by University of Nebraska researchers showed that soybeans genetically altered to resist a popular herbicide produced lower yields than conventional soybeans.

The NU Institute of Agriculture and Natural Resources study showed Roundup Ready soybeans yield 6 percent less than their closest relatives and 11 percent less than high-yielding soybean varieties. That averaged to three fewer bushels per acre – or 480 fewer bushels on a 160-acre field.

Dryland and irrigated studies were conducted at North Platte, Clay Center, Lincoln and Concord comparing Roundup Ready varieties to related varieties and high-yielding traditional soybean varieties. The high-yielding varieties yielded 57.7 bushels per acre, while the variety most closely related to Roundup Ready soybeans yielded 55 bushels per acre. The Roundup Ready soybeans yielded 52 bushels per acre. 

The study showed that Roundup Ready soybeans' lower yields stem from the gene-alteration process. Such a scenario is called yield drag.


2000, March 8 Mississippi State University Extension Service esmarch.html35

Agronomy Notes (Corn).- E. Larson 

FINDINGS: Preliminary research data and industry yield trials suggest the inclusion of a Bt event does not increase hybrid yield potential, as compared a closely related conventional isoline in the absence of corn borers . 

You would not likely recover the higher seed cost of the Bt technology (about $10 per acre) unless significant corn borer infestation is likely. Unfortunately, seasonal corn borer populations are not predictable; therefore, local historical infestation levels should be used to justify Bt hybrid use. 


Looking ahead to crop year 2001, it is likely that the average acre of RR soybeans will be treated with about 0.5 pounds more herbicide active ingredient than conventional soybeans. As a result over 20 million more pounds of herbicides will be applied this crop year…… 

There is voluminous and clear evidence that RR soybean cultivars produce 5 percent to 10 percent fewer bushels per acre in contrast to otherwise identical varieties grown under comparable field conditions to conventional soybeans…. 

Soybean yields have been increasingly erratic across the Cornbelt in recent years. Many fields have suffered yield losses far greater than expected given the magnitude of the RR yield drag. 

The search is on for answers and recently some have emerged. University of Arkansas scientists have shown that root development, nodulation and nitrogen fixation is impaired in some RR soybean varieties and that the effects are worse under conditions of drought stress or in relatively infertile fields.

This problem arises because the bacterial symbiont responsible for nitrogen fixation in soybeans, Bradyrhizobium japonicum, is very sensitive to both Roundup and drought…… 

As new soybean weed control options emerge and are integrated into multitactic soybean weed management systems, fewer farmers will be willing to accept the trade-offs and costs now inherent in selection of a RR variety……

troubled times lie ahead for RR soybeans because the efficacy of glyphosate is clearly slipping in managing weeds and because unanticipated yield penalties are surfacing in some RR fields, traced to how genetic engineers have modified soybean plants to make them Roundup Ready. 

As farmers begin to understand the practical implications of what researchers have recently discovered, interest will grow in other less costly ways to manage soybean weeds….. 

Inserting transgenes into major plant metabolic pathways is a risky proposition that is likely to lead to unanticipated consequences, especially when plants are stressed by unusual weather, pests, or infertile or imbalanced soils…… 

The lack of independent research on the ecological, agronomic and plant defense consequences of RR soybeans, until well after regulatory approvals and widespread market penetration, blindsided regulators and has heightened the vulnerability of farmers.


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