SORPTION OF AMETRYN AND IMAZETHAPYR IN TWENTY-FIVE SOILS FROM PAKISTAN AND AUSTRALIA

Abstract

Sorption of ametryn and imazethapyr in 25 soils from Pakistan and Australia was investigated using the batch method. The soils varied widely in their intrinsic capacities to sorb these herbicides as shown by the sorption coefficients, K_d, which ranged from 0.59 to 47.6 for ametryn and 0.02 to 6.94 for imazethapyr. Generally the alkaline soils of Pakistan had much lower K_d values of both herbicides than the soils of Australia. Both soil pH and soil organic carbon (SOC) were correlated significantly with the sorption of ametryn, whereas only soil pH was strongly correlated with imazethapyr sorption. No correlation was found between K_d values of the herbicides and the clay contents of the soils. Multiple regression analysis showed that K_d values were better correlated (r² = 0.94 and 0.89 for ametryn and imazethapyr, respectively) if SOC and pH were simultaneously taken into account. The study indicated that sorption of these herbicides in the alkaline soils of Pakistan was low and consequently there is considerable risk of groundwater contamination.

Keywords:

• Sorption
• Ametryn
• Imazethapyr
• K_d
• K_oc
• Soil organic carbon
• pH
• Clay

ACKNOWLEDGMENTS

We wish to thank Trevor James for his review of an earlier draft of the manuscript. The senior author greatly acknowledges the World Bank and the Government of Pakistan for financing his doctoral study.