الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
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Summary
This carried out to study the behaviour of some herbicides in
different Egyptian soi s for reducing their pollution to soil and ground water.
The present . vestigation aimed to throw light on the behaviour of
sethoxydim and pen imethalin herbicides in three different soils named clay
soil (Banha), calcareo s soil (El-Nobaria) and sandy soil (Salheia) .
The following oints considered the course of the present investigation:-
1- Adsorptio behaviour time, soil type and herbicide concentration on
adsorption behavio of sethoxydim and pendimethalin in clay, calcareous and
(a) Effect of e
The equilibri
m clay soil and 90
different soils increas
osure time :-
time for sethoxydim and pendimethalin were 120 min.
in. in calcareous and sandy soil . The adsorption on
as the time increased .
(b) Effect of so I type :-
The herbicid pendimethalin showed more adsorption capacity
compared with setho dim at all tested concentrations on the three tested soils,
i.e 92.67 , 82.40 an 69.15 %and 92, 78.87 and 65.75 % with pendimethalin
and sethoxydim in cay, calcareous and sandy soil, with an intial cone. of 4
ug/mL, respectively On the other hand the clay soil adsorbed more herbicides
than the calcareous d sandy soil i.e 92.67 and 92 %, 82.40 and 78.87 %,
69.15 and 65.75 % or pendimethalin and sethoxydim in the case of clay,
calcareous and sandy oils respectively .
The (K) and ) values obtained from pendimethalin and sethoxydim
adsorption isotherm indicated that both of the initial adsorption and the
subsequent adsorptio of clay soil were higher than the calcareous and sandy
soils.
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The distributi n Coefficient (Kd) values for pendimethalin were higher
than . This mean that pendimethalin was adsorbed more
strongly by the soils
2- Down-war movement and leaching of herbicides in soils.
The effect of soil type, herbicides concentration and leaching water
volume on the do -ward movement and leaching behaviour of sethoxydim
and pendimethalin w e studied :-
f both herbicides amounts were located in the upper layer
of the different soils der investigation (0-5 em) were 40.93 ,36.79 and 30..41
sand sady soils respectively 33.97% of sethoxydim were
detected in the leac ate from clay soil 41.36 and 50.44 %were found in the
leachate of calcareo s and sandy soils respectively. On the other hand, 63.71
% of pendimethalin esidue were found in the first layer (0-5 em) in clay soil
60.91 and 45.05 0 in calcareous and sandy soils respectively . The
pendimethalin was clay soil than the calcareous and sandy
soils.
By e concentration of sethoxydim and pendimethalin (500-
1000ug) their amo adsobed on soil surface increased while their residues in
the leachate were de reased . On the other hand increaseing the leaching water
volume decreased se oxydim and pendimethalin adsorption in the first layer
the leachates . Increasing leaching volume
ts of sethoxydim and pendimethalin recovered from the
other layers .
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3- Persistence nd degradation of herbicides in soils :-
The behaviour f herbicides are affected by several physicochemical and
environmental factors
(a) Type of soil and herbicide:
The pendimeth in and sethoxydim were degraded rapidly in clay soil
comparing with calc ous and sandy soils. The differences in sethoxydim and
pendimethalin persist ce among the three tested soils was mainly due to the
great variability in chemical and mechanical properties of these soils.
Sethoxydim and pen methalin persistence were relatively high in sandy soil
y soils. Its amounted 40.81,21.72 % sandy soil 30.42,
17.86 % calcareous d 27.59 , 11.27 %in clay soil of the original doses for
sethoxydim and pen ethalin respectively (after 180 days) . It is interesting to
note that the percent f sethoxydim and pendimethalin residues increased with
increasing the herbici es concentration especially during the late periods after
the application i.e 18 days, 62.61 , 49.46 % in sandy soil, 53.52, 37.75% in
calcareous and 48.83 21.72% in clay soil for persistence of sethoydim and
pendimethalin at conce tration 250 ug/50g respectively.
(b)- Effect of p on sethoydim and pendimethalin degradation :-
Sethoxydim bre down was accelerated in the alkaline medium but
pendimethalin was les affected in this medium pH from 4.5 to 6.8 slightly
affected sethoxydim d pendimethalin degradation increasing the pH above
7.5 increased the the ra of sethoxydim and pendimethalin degradation
4- Microbiologi al degradation of herbicides :-
Autoclaving so’ s, suppressed the degradation of sethoxydim and
pendimethalin as com ared with non autoclaved soils. Sethoxydim was more
---- ~~,----_.~~--
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persistence In tested oils than pendimethalin . Degradation of sethoxydim or
pendimethalin was m re effective in clay soil than in calcareous and sandy
soils according to its high organic content. Degradation of both sethoxydim
and pendimethalin is p ysico-chemical and biochemical processes.