engleski

Extractable residues of atrazine and terbuthylazine in soil after the pre-emergence herbicide application in corn

Dissipation of atrazine and terbuthylazine in herbicide-treated silty loam soils was studied in two corn field experiments conducted in north-western and eastern region of Croatia. Commercial herbicide formulations containing 500 g/L of active component were separately applied to 120 m^2 experimental plots. The plots were treated either with atrazine or with terbuthylazine formulation at a registered application rate of 3 L/ha and at a doubled rate. Each experiment was replicated four times. Soil samples were collected at two depths (0 - 30 cm and 30 - 60 cm) at five different time points: in spring (May) prior to planting of corn and then again immediately after the herbicide application ; 5 months later (October) after the corn harvest ; 10 months later (March next year) before planting and 17 months later (October next year) after the harvest of the spring oats and soybean. Atrazine, terbuthylazine, and their degradation products were extracted from wet soil samples with methanol using a microwave-assisted extraction procedure and analyzed by high performance liquid chromatography with diode-array detection. Under field conditions atrazine and terbuthylazine residues persisted in soil up to 5 and 17 months, respectively. Deethylterbuthylazine residues were also detected 17 months after terbuthylazine application, while dealkylated degradation products of atrazine were not found in any soil sample. The results were evaluated with respect to the physical/chemical properties of analysed compounds, pedological characteristics, and weather conditions possibly affecting the retention/dissipation of atrazine and terbuthylazine in soil.

Atrazine; terbuthylazine; pre-emergence application; soil dissipation; corn field experiments

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