Degradation of formulated and unformulated triticonazole fungicide in soil: effect of application rate

Laboratory incubation studies were conducted to evaluate the influence of commercial formulation adjuvants and application rate over a range of 0.2-80 mg kg(-1) on the dissipation of C-14-triticonazole systemic fungicide in a loamy clay soil, at 22 and 28 degrees C, and 80% of water field capacity. Measurement of the balance of the C-14-residues after incubation at 22 degrees C showed an increased resistance to desorption with time, as apparent desorption K-app increased from 2 to 10 1 kg(-1) in a 133 d period. Decreased extractability of the residues with incubation time and formation of bound residues up to 20% showed that the overall availability of triticonazole decreased with incubation time. The addition of diluted doses of formulation adjuvants did not significantly affect the degradation and binding of the active ingredient. Mineralization of triticonazole was slow, with a high activation energy of 130 kJ mol(-1). The persistence of triticonazole increased with application rate, as the first-order mineralization rates at 28 degrees C decreased from 2 x 10(-3) to 0.7 x 10(-3) d(-1) with amount applied increasing from 0.2 to 80 mg kg(-1). However, the absolute amount of triticonazole mineralized increased with increasing concentration in the soil solution, and the slow mineralization was attributed to limited availability in the soil solution due to high sorption. (C) 1999 Elsevier Science Ltd. All rights reserved.