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Researchers investigate what happens to Bt protein during the agricultural cycle

MON810: Long-term cultivation does not result in an accumulation of Bt protein in the soil

Scientists from the Bavarian State Research Centre for Agriculture (Bayerische Landesanstalt für Landwirtschaft, LfL) and the University of Technology in Munich (TUM) have for the first time investigated what happens to Bt protein from genetically modified MON810 maize throughout the agricultural cycle – from cultivation to use of the plants as cattle fodder, to the spreading of liquid manure from these animals on the fields. The experiments were headed by Dr Martin Müller from the working group on gene transfer and GMO safety research at LfL’s Institute for Crop Science and Plant Breeding.

Dr Martin Müller, Bavarian State Research Centre for Agriculture (Bayerische Landesanstalt für Landwirtschaft, LfL), Institute for Crop Science and Plant Breeding.

Bt protein is known to enter the soil, particularly through rotting plant remains after harvesting. But it is only now that researchers have investigated the extent to which this occurs and whether Bt protein can accumulate in the soil as a result of long-term cultivation. The researchers were unable to find evidence of any accumulation of Bt protein in the soil of trial fields on which Bt maize had been grown for nine years in succession. “Our results show that Bt protein that enters the soil through crop residues breaks down quickly. In the spring before the next crop of maize was sown, we were no longer able to detect any Bt protein on any of the plots,” says Helga Gruber, the scientist in charge of the field trials. To evaluate the trials, the Bavarian researchers developed a special method for detecting the Bt protein in the various sample materials.


Since Bt protein and genetically modified DNA could also enter the soil through liquid manure, the researchers investigated this route as well. First of all, they needed to find out whether Bt protein does in fact enter the soil via liquid manure. Then it was important to find a way of measuring the Bt protein throughout the entire agricultural process.

“Our most important result was demonstrating, firstly, that Bt protein does not accumulate in the soil as a result of long-term cultivation, and secondly, that only minimal residual amounts of Bt protein are contained in the liquid manure spread on the fields. The remaining Bt protein breaks down so fast there that it does not enter the feed again via the harvested crop,” says Helga Gruber summarising the results.

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Photo material

Ten soil samples were extracted using the probe rod for each depth and combined to produce representative mixed samples.

Ten soil samples were extracted using the probe rod for each depth and combined to produce representative mixed samples.

Source: Helga Gruber / www.gmo-safety.eu

Liquid manure was collected over the course of six days from cows fed on Bt maize in a long-term feeding experiment.

Liquid manure was collected over the course of six days from cows fed on Bt maize in a long-term feeding experiment.

Source: Kerstin Steinke / www.gmo-safety.eu

Predefined quantities of liquid manure were taken from the slurry tanks and spread on the trial fields. At the same time, slurry samples were taken for analysis to investigate the effect of slurry storage on the Bt protein.

Predefined quantities of liquid manure were taken from the slurry tanks and spread on the trial fields. At the same time, slurry samples were taken for analysis to investigate the effect of slurry storage on the Bt protein.

Source: Dr. Martin Müller, LfL / www.gmo-safety.eu

Liquid manure from the cows fed on Bt maize was applied to the grassland areas after mowing.

Liquid manure from the cows fed on Bt maize was applied to the grassland areas after mowing.

Source: Dr. Martin Müller, LfL / www.gmo-safety.eu