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

摘要

The effects of herbicides applied at low rates on herbicide residues in soil and roots of sugarbeet were studied in Poland during 2006-07. The following were applied 4 times at 7- to 10-day intervals starting at the onset of weed emergence at recommended and reduced (by approximately 50 and 66%) rates: phenmedipham, desmedipham, ethofumesate, metamitron, triflusulfuron and oil adjuvant. Samples of soil and roots of sugarbeet were analysed for phenmedipham, desmedipham and ethofumesate residues using HPLC with UV detection, and for metamitron residues using GLC with ECD detection. In samples of soil to which recommended herbicide rates were applied, the amount of residues of the active substance of each herbicide ranged from 0.0056 to 0.0124 mg kg-1. The total of amount of residues was 0.0323-0.0373 mg kg-1; in sugarbeet root samples, the corresponding values were 0.0011-0.0085 mg kg-1 and 0.0085-0.0224 mg kg-1. The application of reduced rates (by approximately 50%) decreased the amount of residues by approximately 38-50%, on average. Compared to the recommended rate, a 66% reduction in herbicide rate reduced the residue level by 69-77%, on average. Residues of active substances determined in the roots of sugarbeet did not exceed EU acceptable limits.