Influence of different organic amendments on the degradation, metabolism, and adsorption of terbuthylazine

Abstract

The behavior of the herbicide terbuthulazine (TA) was studied in a clay loam soil after the addition of the addition of different organic amendments (OAs). Addition of poultry compost (PC) and urban sewage sludge (USS) retarded degradation of TA (half-life 55.5 d) compared with its degradation in nonamended soils (half-life 57.3 d). Sterilization of amended and nonamended soils resukted in a partial inhibition of TA led degradation, indicating that biotic and abiotic processes are invloved in TA degradation, indicating that biotic and abiotic processes are involved in TA degradation in soil. Degradation of TA led to the formation of desethyl-terbuthylazine, which was detected in low amounts (< 80% of the initially applied TA) in all soils. Adsorption of TA was relatively low, with K-d values ranging from 2.31 L kg(-1) in the soil amended with USS. In general, K-d values increased with increasing soil amended with USS. In general, K-d values increased with increasing soil organic carbon content. The dissolved organic matter extracted from tho OAs did not appear to interact with the pesticide or the soil surfaces, suggesting that it would not probably facilitate herbicide transport. Desorption studies indicated a slight hysteresis of TA desorption in the amended soils compared with TA desorption in the nonamended soil, which is entirely reversible. These findings might have practical implications for the environmental fate of TA in agricultural soils, where the studied OAs are commonly used.