Evaluating hexaconazole leaching in laboratory and field experiments: effects of application rate, soil type, and simulated rainfall

In the present study we investigated the leaching behaviour of hexaconazole fungicide in two soil packed columns, namely disturbed and undisturbed soil columns in field conditions. The effects of simulated rainfall (100 mL, 200 mL, and 400 mL) and application rate at recommended dosage (4.5 g a.i/palm tree) and double recommended dosage (9.0 g a.i/palm tree) were also studied. The residual of hexaconazole in the soil column was observed to be significantly different between the volumes of simulated rainfall application and decreased with increased soil depth. The highest concentrations were detected at the soil surface (0-10 cm), where 53-63% of the hexaconazole remained after applications. No significant difference was found between the disturbed and undisturbed soil packed column when treated with the recommended and double recommended dosages of hexaconazole. In order to understand the hexaconazole leaching pattern, a field study experiment with the same soil properties and application rate was conducted. The results showed that hexaconazole was distributed downward through the preferential flow and soil crack in the sandy loam soil profile. The groundwater ubiquity scores (GUS) Index for hexaconazole calculated in Malaysian soil was 4.61, indicating that hexaconazole has a high risk of contaminating groundwater resources.