Conversion of DDT to DDD in soil and the effect of these compounds on soil microorganisms

Abstract

DDT was rapidly converted to DDD in submerged soil amended with alfalfa residue. The rate of conversion increased with increasing amounts of alfalfa. In nutrient media, 2 of 10 bacteria and 2 of 10 actinomycetes were completely inhibited by 10 p.p.m. DDT, whereas 4 of 10 bacteria and 6 of 10 actinomycetes were inhibited by 10 p.p.m. DDD. When added to agar in soil dilution plates, 10 p.p.m. DDT or DDD markedly decreased numbers of bacterial and actinomycete colonies. DDD had a broader antimicrobial spectrum and greater toxicity to microorganisms than DDT. However, both compounds had little effect on microorganisms in soil. Fungi were not affected by either compound in culture or in soil.