FIELD AND LABORATORY STUDIES FOR EVALUATING THE TOXICITY OF SOME PESTICIDES ON SOIL MICROORGANISMS.

Incessant and indiscriminate use of some agrochemicals in agricultural production has elicited fears of changes in microbial populations and the activities of individual species of micro-organisms. Present study was carried out to study the effect of three pesticides (Chloropyrifos (1L/200L.Water), Lambada cyhalothrin(50g/100L.Water) and Emamectin benzoate(120g/400LWater)) at field application rate on total population count of microorganism in phasoulus vulgaris field . Also measured the sensitivity of some species, bacteria (Rhizobium leguminosarumBacillus thuringiensis. And ) , fungi (3TTrichoderma harzianum3T and 3TTrichoderma3T viridi)and actinomycetes (5TStreptomyces griseorubens 5Tand 5TStreptomyces5T cavourensis atfield and double application rate to these pesticides .Data indicated that, Chloropyrifos stimulated significantly the proliferation of all of the microorganism. Lambada-cyhalothrin decreased population of Bactria at 1 DAT (day after treatment) until 15 DAT and returned to increase at 21 DAT . For fungal population, the total count of the soil fungi was decreased after the addition of Lambada-cyhalothrin . Actinomycetes was also significantly inhibited during the period from 1 to 15 DAT by Lambada-cyhalothrin, and subsequently recovered to a similar level of control. Emamectin benzoate in general increased population of bacteria and actinomycetes and decreased population of fungi. Concerning the sensitivity study we found that , Chloropyrifos2T inhibited significantly the growth of the tested species at different rates with a positive correlation. 2TChloropyrifos was the most potent compound followed by Lambada-cyhalothrin while Emamectin benzoate did not happen any effect on tested 2Tspecies. For radical growth of 2T3TT.harzianum3T and 3TT.3T viridi Chloropyrifos2T , 2TLambada-cyhalothrin2T and 2TEmamectin benzoate showed the same level in its impact on the bacteria and actinomycetes