Abstract

Effect of agricultural pesticides (Attacke, DD Force,  Chloview ) on  Nitrobacter spp were analyzed in soil using standard toxicological bioassay. Mortality of the test organisms expressed as median lathal concentration (LC₅₀) was used as indices to monitor toxicity. The median lethal concentration (LC₅₀) was employed to compare the toxicities of the different toxicants on the test species. The median lethal concentration (LC₅₀) of the pesticides used decreased in the following order: (Noting that the lower the LC₅₀ the more toxic the toxicant): DD Force  (50.64%) followed by Attacke (54.68%)  and the lowest toxicity  in  Chloview  (57.04%).  Toxicant concentration of 0%, 3.125%, 6.25%, 12.5%, 25%, 50% and 75% at the exposure time of days 1, 7, 14, 21 and 28 were employed. Increase in the percentage log mortality of  Nitrobacter spp in soil amended with three (3) pesticide during the 28 days exposure time to the pesticide concentrations was observed.. The lethal effect (death) of the test organisms could be attributed to the type, concentration, and time of exposure to the toxicant. Pesticides are toxic, disrupt enzymatic activities, affect survival, reproduction, increase individual mortality, decrease fecundity and growth, changes individual behavior such as feeding rate and decrease the overall community biomass, density and generally leads to loss of biodiversity.It  is recommended that the use of chloview pesticide should be encouraged on Nigeria agricultural farm due to its low  toxic effect on Nitrobacter spp as compared to others