Effect of pesticides on most probable number of soil microbes from tea (Camellia sinensis) plantations and uncultivated land enumerated in enrichment media

Abstract

To enumerate the most probable number (MPN) of soil microbes from tea [Camellia sinensis (L.) O. Kuntze] plantations anduncultivated land, soil samples were plated into enrichment media designed to promote cellulolytic, nitrogen-fixing orsulphur.-oxidizing groups. The experiment was conducted in 1990-91 by collecting fresh soil samples 6 times a year to coverall the seasonal variations. To study the effect of pesticides, each sample was introduced into soil dilutions 24 hr beforeplating into the respective enrichment medium. The population of sulphur-oxidizing strains increased in the presence ofmalathion and dimethoate and reduced in the presence of fenitrothion and endosulfan. All the pesticides tried reduced thepopulation of nitrogen-fixing strains. Glyphosate and 2,4-D increased the population of cellulolytic strains but dalapon andparaquat reduced it.