A laboratory study of the mineralization and binding of C-14-labeled herbicide rimsulfuron in a rendzina soil.

The fate of pyrimidine-2-C-14-rimsulfuron in a rendzina soil was investigat ed using a laboratory microcosm approach. Measurement of CO2 evolution sugg ested that rimsulfuron applied at 5 times the recommended dose did not affe ct soil respiration. Under abiotic conditions, no mineralization of C-14-ri msulfuron into C-14- CO2 occured and under biotic ones it was very low reac hing 0.75 % of the applied C-14-rimsulfuron after 246 days of incubation. T he analysis of data showed that a three-half order model provided the best fit for the mineralization curve. Extractable C-14-residues decreased over time to 70 - 80% of the applied C-14- rimsulfuron at the end of the incubat ion. After 246 days of incubation, non extractable residues (NER) accounted for up to 24.7 % of the applied C-14-rimsulfuron and were distributed acco rding to organic carbon in soil size fractions, suggesting a progressive in corporation process of NER to soil humus. (C) 1999 Elsevier Science Ltd. Al l rights reserved.