Effect of Sulfonylureas Residues on the Lupine and Vigna Seedlings Development during Biotesting Research on Sod-Podzolic Soil

In a series of consecutive vegetation experiments on biotesting on samples of sod-podzolic cultivated soil after its treatment with herbicides from the class of sulfonylureas: Magnum, VDG, metsulfuron-methyl 600 g/kg, manufactured by August and Alistair Grand, MD, diflufenican 180 g/l + mesosulfuronmethyl 6.0 g/l, iodosulfuron-methyl-sodium 4.5 g/l + mephenpyrdiethyl 27 g/l (antidote), manufactured by Bayer. The residual phytotoxicity of these preparations for seedlings of sensitive cultures of white lupin (Lupinus albus) and masha (Vigna radiata) was studied. The initial soil samples were taken in the field on the 5th day after herbicides were applied in the field in winter wheat crops using 2 different tillage technologies: traditional on the basis of dump plowing and zero tillage. According to the results of biotesting samples at a temperature of 20°C and humidity at the level of 60% soil moisture capacity, it was shown that the half-life of herbicides (DT₅₀) was reached after 40 ± 3 days of incubation, and detoxification to the level of 70–80% occurred 200–240 days after the introduction of herbicides into the soil. Regardless of the method of tillage and the applied herbicide, 2 years after the application of herbicides, the suppression of test crops at the level of  >10% of the control was detected. White lupin and mash are highly sensitive to the effects of micro-quantities of herbicides of the sulfonylurea group, therefore it is recommended to use these test cultures to determine the residual phytotoxicity of the soil. The manifestation of the aftereffect of sulfonylureas on legumes is shown, which is important even in specialized crop rotations designed for zero tillage.