الفهرس 
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Abstract
The use of pesticides is an accepted practice In the modem agriculture.
Although insecticides are used in smaller quanitities than the herbicides, they are
generally much toxic to mammals. In the present study, an attempt to evaluate the
effect of some insecticides (Sevin. Larvin and Lannate) on the densities of certain
bacteria (azotobacter and denitrifying bacteria) in soil and on some soil properties,
their degradation or detoxification is consequently important. The carbamate
insecticides, Sevin, Larvin and Lannate were applied in (I nad IO-fold offield
recommended dose) glucose amended and unamended soil samples. Also, the
effect of these insecticides on the biological activities of selected bacteria and their
persistance were investigated and the results were as follows:
1- The total bacterial counts increased in both glucose amended and unamended
and insecticide treated and untreated soil samples, reaching the maximum after 5
days incubation time and then decreased
2- In presence of Sevin, Larvin, and Lannate, the azotobacter counts increased by
time recording the highest counts after 5 days incunbation, in both glucose
amended and unamended soil samples and then decreased with time.
3- The denitrifing bacterial counts were high In glucose amended soil In the
presence or absence of the tested insecticides.
4- The effect of the tested insecticide on the chemical properties of soil inoculated (a) No significant effect of all insecticides tested on the organic carbon of the clay
loam soil along the experimental condition used.
(b) The highest values of CaC03 were recorded after one day in control samples as
well as in the amended insecticide treated soil samples inoculated with microbs.
(c) The tested insceticides (Sevin, larvin & lannate) had no significant effect on
carbonate contents ..
(d) The bicarbonate contents recorded the highest values after one day incubation
time in glucose amended and unamended and insecticide treated and untreated soil
samples.
(e) The highest values of total soluble salts were recorded after one day of
incubation only in glucose amended control as well as glucose amended insecticide
treated soil samples.
5- Two nitrogen fixer orgarusm were isolated, characterized and identified as
Azotobacter. chroococcum. ~, A15
(a) The effect of Sevin, Larvin, and Lannate on the growth of the two Azotobacter.
chroococcum strains was studied. Compared to control both Sevin and Larvin had
negative effect on Azotobacter . chroococcum ~ growth, while 150 ug/ I:00 ml
culture medium of Lannate stimulate growth of this organism after one day
incubation. Using Sevin and Lannate at the tested doses after 15 days incubation
time, the growth of Azotobacter chroococcum A15 was stimulated, while at
Larvin dose of 500 ~g/ 100 mI culture medium and after incubation periods of 1
and 10 days, higher growth rates of the organisms compared to control were
recorded.
(b) The amounts of fixed nitrogen by Azotobacter chroococcum As were
increased after 5 or 10 days incubation time in the presence of the tested doses of Sevin or the recommended dose of Larvin or Lannate. Compared to control, the
amounts of fixed nitrogen by Azotobacter chroococcum AlS were high in the
presnece of the recommended dose of the different time intervals tested. The
insecticide Larvin at its tested dose and at the different incubation periods had a
depressing affect on the nitrogen fixation by Azotobacter chroococcum Ais. On
the other hand Lannate stimulate the nitrogen fixation by this bacterium when
used at the recommended dose and 5-fold after 5 days incubation.
(c) Both Sevin, Larvin and Lannate at the field recommended dose stimulate the
arnmonical nitrogen production by Azotobacter Chroococcum ~ where: the
highest amounts were recorded after 10 days incubation time. Also, The
production of ammoniacal nitrogen by Azotobacter chroococcum AIS in the
presence of the tested insecticides, follows the same pattern as in Azotob.acter
chroococcurn A4
(d) The amounts of amino nitrogen produced by Azotobacter chroococaim ~
using the different doses of Sevin, Larvin and Lannate ,recorded their highest
values after 5 days of incubation. On the other hand, using both Sevin and Larvin
at 5-and 10-fold the recommended dose, .the amino nitrogen production by
Azotobacter chroococcum AIS was stimulated to levels higher than control at the
different time intervals. Also, the insecticide Lannate stimulated the amino nitrogen
produced by this bacterium at doses 5-and 10-fold the recommended dose after
incubation periods of 5 days.
(e) The ascorbic acid production by Azotobacter chroococum ~ was increased by
using the doses of the insecticide Sevin and 5-fold the recommended dose of larvin
and lannate after incubation period of 15 days. The ascorbic acid production by
Azotobacter chroococcum A1S was increased by using of Sevin or Larvin at doses
of recommended dose, 5-fold and 10-fold after 5 days incubation time. Using Lannate at doses of30 & 300 Ilgl100 ml culture medium after incubation periods
of I and 5 days, respectively, the ascorbic acid production by this organism was
Increase.
(f) The production ofIAA by Az. chroococcum ~ and AI5 reached its maximum
using the various tested doses of Sevin, Larvin or Lannate after one day
incubation time.
(g) The persistency of Sevin, Larvin and Lannate in cultures, inoculated soil
samples and cell-free extract of Azotobacter chroococcum ~ and Al5 was
investigated. The persistancies of the tested insecticides using Azotobacter
chroococcum A4 in culture medium, cell-free extract and inoculated soil samples
were lower than those using Azotobacter chroococcum Al5 by which higher
values of insecticide residues were determined. Compared to each other, the
insecticide Larvin was more stable than Sevin, and Lannate was the most labile one
using both organisms under the experimental condition tested.