Investigations on the formation and distribution of non-extractable residues of dithianon

Degradation studies were conducted with the radiolabelled fungicide dithian on under standard conditions for 64 days. The microbial activity of the soi l was stimulated by an amendment of maize straw simulating post-harvest con ditions. This addition of an easily available carbon source decreased the m ineralization of the compound initially. At the end of the incubation perio d, however, the mineralization rate was higher in the straw amended soil co mpared to the control. The compound is characterized by mineralization loss es of approx. 33 % and the formation of nonextractable (bound) residues of approx. 63 % in 64 days. The addition of organic material increased the amo unt of labelled organic carbon in the easily available fraction (light frac tion LF) but decreased the amounts of non-extractable radioactivity in the clay and silt fraction of the soil. In total the amount of nonextractable r esidues was similar in both treatments.