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

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

Abundance and diversity of ammonia-oxidizing bacteria in relation to ammonium in a Chinese shallow eutrophic urban lake

The measures of most-probable-number and restriction fragment length polymorphism analysis were used to analyze the abundance and diversity of ammonia-oxidizing bacteria in sediment of a Chinese shallow eutrophic urban lake (Lake Yuehu). Among the 5 sampling sites, ammonia concentration in interstitial water was positively proportional not only to the content of organic matter, but also to ammonia-oxidizing bacteria numbers (at a magnitude of 10(5) cells g-1 dry weight) in sediment significantly. Furthermore, the diversity of ammonia-oxidizing bacteria were determined by means of PCR primers targeting the amoA gene with five gene libraries created and restriction pattern analysis. The 13 restriction patterns were recorded with 4 ones being common among all sampling sites. The 8 restriction patterns including 4 unique ones were found at the site with the highest NH4+ concentrations in interstitial water, while, there were only common patterns without unique ones at the site with the lowest NH4+ concentrations in interstitial water. Phylogenetic analysis showed that the amoA fragments retrieved belong to Nitrosomonas oligotropha & ureae lineage, N. europaea lineage, N. communis lineage and Nitrosospira lineage, most of which were affiliated with the genus Nitrosomonas. The N. oligotropha & ureae-like bacteria were the dominant species. Thus, the abundance and diversity of sediment AOB is closely linked to ammonium status in eutrophic lakes.

Ammonification and nitrification of biuret in soils at different moisture levels

In laboratory experiments under three moisture levels [50, 200 and 400% whc] with sandy, sandy loam and clay loam soils, the ammonification and subsequent nitrification of 200 ppm biuret-N was studied. Ammonification was more rapid in heavy than in light textured soils. Mineralization percentages of biuret-N were 25, 27 and 30.2 at 400% whc, in sandy, sandy loam and clay loam soil, respectively, and most mineralized-N was in the form of NH4 +. The corresponding figures at 50% whc were 15, 16 and 21% and most nitrogen was in the NO3 form. NO-2-N accumulated in considerable amount only at 200% whc, and persisted longer in soils which reflect the relative sensitivity of Nitrobacter to anaerobic conditions. Whc, of 400%, inhibited both Nitrosomonas and Nitrobacter and no NO-2 or NO-3 was detected in the soils. Biuret, by itself, at 200 ppm-N had no effect on nitrifying bacteria