EFFECT OF DIAZINON APPLICATION ON SOIL PROPERTIES AND SOIL MICRO FLORA

Abstract

Rhizosphere (Rh) and Subsurface (Ss) soil samples were treated with diazinon for 30 days in the laboratory to determine the effect of the chemical on the soil physico-chemical properties and microbial populations. The pH, organic carbon, nitrogen, and phosphorus of both rhizosphere and subsurface soil increased from the 10th day to 30th day of treatment with a highest increment of 10- fold recorded in Phosphorus parameter of Subsurface soil sample and 6- fold increment in organic carbon content of Subsurface all at 20th day of diazinon treatment. There was an initial rise in bacterial population in the two treated soil samples thereafter a decline, while fungi population decreased with days of diazinon application.Marked reductions in microbial load were recorded in the treated soils as compared to control soil samples. Ten bacterial isolates and five fungal species were identified in the control rhizosphere soil, while in the treated rhizosphere soil only eight bacterial isolates representing 60% and two fungal species representing 40% survived diazinon treatment.
Also six bacterial isolates and five fungal species were identified in the control Subsurface soil samples, while in the treated Subsurface soil sample only four bacterial isolates representing 60% and two fungal species representing 40% survived the diazinon treatment. In Rh &Ss, Penicillium sp, Rhizopus sp., and Fusarium sp., Mucor sp., Rhizobium sp., and Nitrobacter sp. isolated in all the control soil samples were inhibited in all the treated Rh and Ss soil samples.