Leaching of pesticides through normal-tillage and low-tillage soil--a lysimeter study. I. Isoproturon

• Published in: Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes Vol. 38; no. 1; pp. 1 - 18
• Main Authors: Fomsgaard, I.S, Spliid, N.H, Felding, G
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01-01-2003; Taylor & Francis
• Subjects: Agriculture; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Carbon Radioisotopes; clay soils; conventional tillage; Crops, Agricultural - chemistry; Crops, Agricultural - metabolism; Denmark; Environmental Monitoring - methods; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Groundwaters; herbicide residues; Herbicides - chemistry; Herbicides - metabolism; Humans; Isoproturon; Leaching; Low-tillage; Lysimeter; lysimeters; metabolites; Methylurea Compounds - chemistry; Methylurea Compounds - metabolism; Natural water pollution; Normal-tillage; Pesticide; Phenylurea Compounds; Pollution; reduced tillage; Seasons; Soil; Soil - analysis; Soil and water pollution; soil chemical properties; Soil Pollutants - analysis; Soil science; Water - analysis; Water treatment and pollution; Weather; Denmark; Europe; Denmark, Sjaelland, Vestsjaelland, Flakkebjerg; Cultural practice; Isoproturon; Pesticides; Lysimetry; Soil pollution; Leaching; Herbicide; Lysimeter; Normal-tillage; Plowing; Soils; Low-tillage; Pesticide; Soil; Ureas; Sandy loam soil; Ground water
• ISSN: 0360-1234; 1532-4109
• DOI: 10.1081/PFC-120016602

Isoproturon is a herbicide, which was used in Denmark against grass weeds and broad-leaved weeds until 1998. Isoproturon has frequently been detected in ground water monitoring studies. Leaching of isoproturon (N,N-dimethyl-N′-(4-(1-methylethyl)phenyl)urea) and its metabolites, N′-(4-isopropylphenyl)-N-methylurea and N′-(4-isopropylphenyl)urea was studied in four lysimetres, two of them being replicates from a low-tillage field (lysimeter 3 and 4), the other two being replicates from a normal tillage field (lysimeter 5 and 6). In both cases the soil was a sandy loam soil with 13-14% clay. The lysimetres had a surface area of 0.5 m
2
and a depth of 110 cm. Lysimeter 3 and 4 were sprayed with unlabelled isoproturon while lysimeter 5 and 6 was sprayed with a mixture of
14
C-labelled and unlabelled isoproturon. The total amount of isoproturon sprayed onto each lysimeter was 63 mg, corresponding to 1.25 kg active ingredient per ha. The lysimeters were sprayed with isoproturon on October 26, 1997. The lysimetres were installed in an outdoor system in Research Centre Flakkebjerg and were thus exposed to normal climatic conditions of the area. A mean of 360 l drainage water were collected from lysimeter 3 and 4 and a mean of 375 litres from lysimeter 5 and 6. Only negligible amounts of isoproturon and its primary metabolites were found in the drainage water samples, and thus no significant difference between the two lysimeter sets was shown. In a total of 82 drainage water samples, evenly distributed between the four lysimetres isoproturon was found in detectable amounts in two samples and N′-(4-isopropylphenyl)urea was found in detectable amounts in two other samples. The detection limit for all the compounds was 0.02 μg/l. 48% and 54% of the added radioactivity were recovered from the upper 10 cm soil layer in lysimeter 5 and 6, respectively, and 17 and 14% from 10-20 cm's depth. By extraction first with an aquatic CaCl
2
solution 0.49% of the added radioactivity was extracted from the upper 10 cm layer in lysimeter 5. In the subsequent extraction with acetonitril, 1.19% of the added radioactivity was ekstracted. In lysimeter 6, upper 10 cm, 0.2% were extracted with water and 0.56% were extracted with acetonitril. Below 10 cm's depth no measurable amounts could be extracted.