Behaviour of metamitron and hydroxy-chlorothalonil in low-humic sandy soils

✍ Scribed by van der Pas, Leo J T; Matser, Arriënne M; Boesten, Jos J T I; Leistra, Minze

• Book ID: 101215719
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 173 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199909)55:9<923::aid-ps37>3.0.co;2-n

✦ Synopsis

The behaviour of the herbicide metamitron and of the main transformation product, hydroxy-chlorothalonil (HTI), of the fungicide chlorothalonil was studied to assess the risk of leaching from low-humic sandy soil. The adsorption of metamitron corresponded to a K om value of about 60 dm 3 kg À1 (moderate adsorption). The half-life of metamitron in soil at 15 °C was only three days, presumably due to adaptation of the micro-organisms. In the autumn, the residue of metamitron in the soil pro®les corresponded to less than 1% of the cumulative dosage. The half-life of chlorothalonil at 15 °C was about 12 days and about 45% of it was transformed to HTI. The adsorption of HTI to the soils corresponded to a K om value of 260 dm 3 kg À1 . The incubation study (15 °C) showed the transformation of HTI in the soils to be very slow. The amounts of HTI remaining in the soil pro®les in the autumn corresponded to 4 and 16% of the cumulative dosage of chlorothalonil. In winter, the HTI residue decreased by 40% relative to the autumn level. Occasionally, HTI could be detected in the upper ground-water level (at a depth of about 1 m), at an average concentration of 0.1 to 0.2 mg dm À3 .