Micro-rates of herbicides used in sugar beet crop - influence on herbicide residues level in roots and soil

Abstract: The aim of present investigation was to evaluate the influence of lowrates application on herbicide residues in soil and roots of sugar beet. Chemical weed control in sugar beet was applied at recommended and reduced (about 50 and 66%) doses of herbicides including substances such as: phenmedipham, desmedipham, ethofumesate, metamitron, triflusulfuron and oil adjuvant applied 4 times at 7-to 10-day intervals starting at the onset of weed emergence. Samples of soil and roots of sugar beet were taken at the day of lifting. Phenmedipham, desmedipham and ethofumesate residues were analysed using HPLC with UV-detection. Metamitron residues were analysed using GLC with ECD detection. At lifting time, in soil samples, where recommended herbicide doses were applied, the residues of separate active substance of herbicides amounted from 0.0056 to 0.0124 mg . kg -1 . Sum of all detected residues of applied substances amounted 0.0323-0.0373 mg . kg -1 . In sugar beet root samples, the residues amounted respectively 0.0011 to 0.0085 mg . kg -1 and 0.0085-0.0224 mg . kg -1 . Application of the reduced doses by about 50% influenced on a significant decrease of residues about 38-50% average. For samples, where reduction of herbicide dose amounted 66%, the decrease of residues level, in comparison with results obtained at recommended doses, was statistically significant and amounted 69-77% average. Residues of active substances determined in roots of sugar beet did not exceed EU acceptable limits