BEHAVIOR OF THE FUNGICIDE DEXON IN SOIL

Abstract

The behavior of fungicide Dexon (p-dimethylaminobenzenediazo sodiumsulfonate) in soil was studied. The fungicide disappeared from soil within 100 days.Dexon application slightly stimulated the total counts of bacteria, actinomycetes and fungi. The fungicide inhibited the conversion of nitrite to nitrate more intensely than that of ammonia to nitrite. At the same time nitrite oxidation by resting cells of Nitrobacter winogradskyi was not affected by this fungicide as revealed by manometric studies. In view of these observations the suggestion that Dexon affects mainly the heterotrophic nitrification in soil is made. N, N-Dimethyl- p-phenylenediamine(DMPDA) which was earlier found to be the first breakdown product of Dexon was noted to be equally toxic to  Pythium, the pathogen against which Dexon is mainly used.