[Study the effect of insecticides commonly used locally on the bacteria of economic importance in the soil]

ABSTRACT

This study aims to identify the effect of different concentrations of insecticides the common dorspan and decis on the total number of Nitrosomonas, Nitrobacter and cellulose degradation bacteria in the soil during the winter and spring of the agricultural season 2012/2013 has been selected for two insecticide fixed rates [half - the same - twice] concentration, was treated soil with two insecticide both individually and prescribed for each concentration of insecticide using spraying machine 10-liter, with a smaple treatmen without. Results insecticides showed its effect on bacterial groups, and has been associated it effect by quantity additive concentration, dropped the numbers of Nitrosomonas, Nitrobacter and cellulose degradation at twice and provided for it, that continued period of time after soil treatment to make sure their influence in general and not because of decline amount of the required nitrogen for the decompose of organic carbon, while it did not affect half concentration of two insecticides on the numbers of Nitrosomonas and degradation of cellulose bacteria, it returned to increase in recent weeks indicating the biodecomposition of insecticide and there is no inhibitory effect of this concentration on the two groups. For Nitrobacter, the numbers decreased in the half concentration of two insecticides in recent weeks after increase it in the first few weeks but dorspan returned to the increase in the last week which shows the cumulative effect of Decis, while dorspan decline the numbers by decreasing the amount of the insecticide and the occurrence of biodecomposition and there is no accumulative effect of this insecticides. Comparing insecticides show that the effect of high concentrations of two insecticides similar on the number of economically important groups, while differed effect the half concentration on Nitrobacter for Nitrosomonas and degradation of celluiose bacteria, which were similar in this concentration too Through statistical analysis shows that there is a highly significant of the interaction between the type of insecticide and concentration, and the insecticide depends on the concentration to show the impact on the numbers of Nitrification and cellulose degradation bacteria at the level of of significance 0.05