engleski

Spatial and temporal distribution of terbuthylazine in a herbicide treated corn field soil

The vertical distribution of terbuthylazine and its metabolite deethylterbuthylazine was evaluated in four layers of a silty loam agricultural soil during a five-month period of corn cultivation. The experimental field plots were treated pre-emergence with a suspension of terbuthylazine formulation Radazin TZ-50 at a regular (1.5 kg/ha) and a double-regular rate. The soil samples were collected every 7 to 20 days at depths of 0 to 10 cm, 10 to 20 cm, 20 to 30 cm and 30 to 50 cm. Herbicide residues were extracted from wet soil samples with methanol using a microwave-assisted extraction procedure and then analysed by liquid chromatography with UV diode-array detection. In the first three months after herbicide application the loss of terbuthylazine from the surface soil (0-10 cm) was significantly affected by the soil moisture content. Seven days after application at regular and double-regular rate 56 % and 70 %, respectively, of the initial terbuthylazine amount dissipated from the first 50 cm of soil. Five months later, at the time of corn harvest, the total loss of terbuthylazine from soil was 96 % at both application rates. The dissipation rate of terbuthylazine was higher in upper soil layers and correlated significantly with the higher soil organic carbon content. Terbuthylazine dissipation was also favoured by the higher herbicide application rate.

Terbuthylazine; agricultural soil; application rate; dissipation rate

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