Abstract

A pot culture experiment was conducted to investigate the effect of pesticides – 2,4-D (herbicide), endosulfan (insecticide) and dithane M-45 (fungicide) at their field application rates (1.0, 2.0 and 1.5 kg a.i ha^-1), respectively, on the available Diethyl Triamine Pentacetic acid (DTPA) extractable copper (Cu), manganese (Mn) and zinc (Zn) along with the population of viable bacteria and fungi in new alluvial soil (Typic haplustepts). The results reveal that as compared to control, 2,4-D effectuated a significant increase in the population of total bacteria (up to 21.1%) and fungi (33.7%) besides available Cu (21.7%) and Zn(119.4%) during later stages and Mn (8.7%) almost throughout the incubation period though there was significant progressive immobilization of Cu (17.7%) during initial stages. Endosulfan, contrarily caused significant reduction of total bacteria (up to 18.4%), fungi (13.1%) and immobilization of Zn (42.1%) during later stages, Cu (10.3%) in the intermediary stage and Mn (64.7%) almost  throughout. Dithane M-45, however, resulted in a significant increase in available Cu (13.2%) and Mn (3.38%) in the intermediary stage in spite of inducing detrimental influence on fungi (18.7%) and immobilization of Zn (12.9%) during intermediary stage and Mn in early (3.0%) and late stages (6.7%) of incubation. Among the pesticides used in the investigation, the performance of herbicide (2,4-D) was encouraging in almost every aspect.

Key words: Pesticide, DTPA extractable Cu, Mn and Zn, viable bacteria and fungi