Glyphosate residues in grain after desiccation of crops in the Ob Region

Abstract

The residual amounts of glyphosate in wheat grain after desiccation of crops were determined. Glyphosate is the most widely used herbicide in the world. The level of its ecotoxicity is widely discussed in the scientific literature after the compound was classified as “a likely carcinogenic” pesticide. It is assumed that glyphosate residues can be highest when the crops are desiccated before harvesting. The studies were carried out in 2018 (central forest-steppe of the Novosibirsk Ob region (54°53'13.5"N, 82°59'36.7"E). In the experiment, desiccation of wheat was carried out with the herbicide Zero Super (the content of isopropylamine salt of glyphosate was 750 g/kg) at the recommended dose of 1.5- 2.0 kg/ha. Glyphosate residues in plant biomass were determined using the test system, based on the principle of enzyme immunoassay. Pre-preparation of the samples for the analysis was carried out according to the recommendation of Stylab laboratory, which validated the method for the determination of glyphosate in grain. Glyphosate residues were found in all of the 37 samples tested. Regardless of the sampling period after desiccation, herbicide residues in the grain did not exceed 4.4 mg/kg. In 14 days after desiccation, the minimum pesticide level was lower (0.5 mg/kg) compared to the data obtained in 7 days (2.6 mg/kg). The content of the herbicide residues in wheat straw was higher than in grain. The highest values of glyphosate residues were found in the dry biomass of weed vegetation (up to 9 mg/kg). In the grain stored for 1 year, the content of GR has not decreased. The data obtained were compared with the MRL for the residual amount of glyphosate in wheat grain accepted in the world.