• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.85-89
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• 1998

Effect of soil residue paraquat (1,1-dimethyl-4,4-dipyridinium dichloride) on growth of barley (Hordeum vulgare L. cv. Sacheon No.6 and cv. Tapgolbori) and soybean [Glycine max (L.) Merr. cv. Alcheon and Danyeop] was investigated. Changes in soil residue paraquat during the cultivation period and residue amount in the p1ants at harvest were also determined. Experiments were conducted at two paraquat residue conditions; the first was done in an apple orchard soil where paraquat residue recorded 30.2 ppm in 1996, but decreased to about 9 to 9.8 ppm at the time of crop seeding and the second was conducted in the soil fortified to about 27 to 32 ppm paraquat residue. In both conditions, no crop injury due to the residue paraquat was observed and number of emerged seedlings and plant height of the two crops were not affected by soil residue paraquat. Residue amount of paraquat in the plants occurred less than 0.5 ppm detection limit. At the first condition, soil residue paraquat was further slightly decreased for 90 days after seeding, while no great change in the residue level was found at the second condition for 30 days after seeding. The results suggest that no carry-over effect occurs at about 30 ppm of soil residue paraquat and at present crop cultivation in Korean orchard soils are safe with respect to crop growth and paraquat residue in the plants.

• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.90-95
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• 1998

Soil residues of paraquat (1,1-dimethyl-4,4-dipyridinium dichloride) were determined in apple, pear, grape, and peach orchards for which 15 sites each were selected randomly from the corresponding large-scale production area throughout the country. Strong adsorption capacity measured using wheat bioassay (paraquat concentration required to reduce 50% root growth of wheat, SAC-WB) was also investigated on the orchard soils and the paraquat residue level was calculated against total SAC-WB values (SAC-WB value + paraquat residue). Average bound residue of paraquat on the 60 sites was 6.9 ppm, while paraquat residue in apple orchard reached 20.2 ppm which was the highest among the orchards and was almost double as compared with those in the other three orchards. Loosely bound residue of paraquat determined on the bound residue high top five soils occurred less than 0.5 ppm detection limit. Average SAC-WB value was 276.1 ppm and there were no any correlations between the SAC-WB value and clay content, organic matter content, and cation exchange capacity of the orchard soils. Paraquat residue level of the orchard soils against total SAC-WB recorded 2.43%.

• The Korean Journal of Pesticide Science
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• v.3 no.1
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• pp.66-77
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• 1999

In order to elucidate the fate of the residues of the bipyridylium herbicide paraquat in soil, maize plants were grown for 4 weeks on the specially-made pots filled with two different types of soils containing fresh and 6-week-aged residues of [$^{14}C$]paraquat, respectively. The mineralization of [$^{14}C$]paraquat to $^{14}CO_{2}$ during the aging period and the cultivation period of maize plants amounted to $0.13{\sim}0.18%$ and $0.02{\sim}0.17%$, respectively, of the original $^{14}C$ activities. At harvest the roots and shoots contained less than 0.1% and 0.01% of the originally applied $^{14}C$ activities, respectively, whereas the $^{14}C$ activities remaining in soil were more than 97% in both soils. The water extractability of the soil where maize plants were grown for 4 weeks was less than 1.2% of the original $^{14}C$ activities. Most of the non-extractable soil-bound residues of [$^{14}C$]paraquat were incorporated into the humin fraction. Soil pHs during the aging of soil B and after cultivation in all treatments increased. The distribution of the $^{14}C$ activities in subcellular particles of the maize plant roots was the highest in the residue fraction(incompletely homogenized tissue). Dehydrogenase activities increased after vegetation, regardless of soil aging.