الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 106 |  |  |
| | | from | 106 | | |
Abstract
The current work was conducted to study the behaviour of zinc, nickel and lead in soils as a result of increasing their salinity or sodicity.
A top soil sample (0 — 20Cm) was obtained from the farm of Agricultural Research Center at Giza to develop the soil models needed for these study.
Portions of composite soil sample were treated with equivalent amounts of NaCI + CaCI 2 salts to achieve three grades of salinity corresponding to EC values in the saturation extract of 4, 8 and 12 dSnfl . Other portions of the composite soil sample were treated with different concentrations of NaHCO3 solution to obtain different levels of soil sodicity corresponding to ESP values of8.8 , 20 , 30 , 40 and 50%.
The artificially salinized and sodified soil models were analyzed for total salinity and sodicity in terms of EC and ESP.
An incubation trail was set up using the prepared soil samples to determine the changes in availability of Zn,Ni and Pb due to the variations in both EC and ESP under different periods of incubation.
Also a greenhouse experiment was conducted using the previously prepared saline and sodic soil samples as growth media , where sorghum plants were grown for 45 days, thereafter the dry
matter as well as the concentration and uptake of Zn,Ni and Pb by plants were estimated.
The results obtained can be summarized in the following : (A) Under saline conditions:- (i):The incubation experiment:-
1- DTPA — extractable Zn sharply and consistently decreased with increasing salinity from EC, of 4 up to 12 dStill,but it significantly decreased with prolonging the time of incubation from 15 up to 90 days.
The interactive effect of soil salinity and incubation period on available Zn can be described by the following equation:
Available - Zn = 7.34 — 0.0168 days + 0.120 EC ( R=0.261* )
2-Increasing soil salinity level to 12 dSnil significantly reduced the amount of DTPA — extractable Ni .
The relationship between available- Ni and incubation period could be represented by the following equation :
Available-Ni = 1.96 — 0.00957 days ( r = - 0.465***)
The interaction effect of soil salinity and incubation period on available — Ni is described by the equation ;
Available- Ni = 1.92 — 0.00957 days + 0.0038 EC ( R = 0.466***)
3- DTPA — extractable Pb significantly decreased with increasing soil salinity as compared with the control treatment, (normal soil).
The relationship between available — Pb and incubation period
could be described by the following equation:-
Available — Pb = 4.51 + 0.0181 days . (r = 0.285*)
The combined effect of soil salinity and incubation period was
assessed by the equation;
Available—Pb = 4.44 +0.0181 days + 0.0079 EC ( R = 0.285*) (ii) The greenhouse experiment:-
1-The dry matter of yield of sorghum plants was significantly reduced
as the soil salinity increased .
The interactive effects of each of the applied Zn ,Ni , and Pb and
soil salinity on dry matter yield sorghum plants were described by the
following equations:-
-With Zn application:
D.M.yield — Zn = 2.62 — 0.225 EC (r = - 0.940*** )
-With Ni application: D.M. yield — Ni = 2.84 — 0.252 EC ( r = - 0.916*** )
-With Pb application:
D.M. yield — Pb = 2.65 — 0.233 EC ( r = - 0.928*** )
2- Zn- concentration in sorghum plants was significantly and gradually reduced with increasing soil salinity .
Sianntary 55
The relationship between soil salinity and Zn-concentration in sorghum plants could be statistically described by this equation:
Zn- concentration = 87.2 — 2.53 EC ( r = - 0.919*** )
3-Increasing soil salinity resulted in gradually decrease in Ni—concentration in sorghum plants .
4-Pb - concentration in sorghum plants was significantly increased with increasing soil salinity .
The effect of soil salinity on Pb-concentration of sorghum plants was represented by this equation:
Pb — concentration = 3.76 + 0.429 EC ( r = 0.828***)
5-Zn — uptake by sorghum plants was significantly and negatively affected by increasing salinity levels of the tested soil models . This trend could be described by the following equation:
Zn- uptake = 207 —17.6 EC ( r = -0.937***)
6-Ni- uptake by sorghum plants was significantly and dramatically reduced as a result of increasing soil salinity . The influence of soil salinity on nickel uptake by sorghum plants could be represented by following the equation:
Ni — uptake = 25.8 — 2.29 EC ( r = - 0.867***)
7- Pb- uptake by sorghum plants was significantly and sharply diminished with augmenting soil salinity . The regression equation described this relationship was :
Pb- uptake = 13.70 — 1.17 EC ( r = -0.840*** ) (B) Behaviour of Zn , Ni and Pb under sodic conditions:- (i) The incubation experiment:-
I-The available -Zn decreased significantly by increasing ESP from 8.8 to ESP 30.The interactive effect of soil sodicity at different incubation periods could be represented by the multiple regression
equation:-
Available-Zn = 10.10 — 0.0198 days — 0.0249 ESP (R= 0.281*)
2-DTPA — extractable Ni significantly increased as the soil sodicity increased from ESP of 20 up to 50 .
This trend could be summarized by the following equations : Available — Ni = 1.18 + 0.0269 ESP ( r = 0.416**)
Available - Ni = 2.76 — 0.016 days ( r = - o.493*** )
Available - Ni = 1.96 — 0.016 days + 0.0269 ESP (R= 0.646*** )
3- DTPA — extractable Pb was significantly increased by increasing soil sodicity up to ESP 40% .
This finding could be represented by the following equations: Available — Pb = 5.68 + 0.0482 ESP ( r = 0.505*** )
The effect of incubation period on available- Pb could be summarized by this equation:
Available — Pb = 5.92 + 0.0244 days ( r = 0.508 *** )
The interactive effect of soil sodicity and incubation period on availability of lead could be represented by the multiple regression equation:
Available — Pb = 4.49 + 0.0244 days + 0.0482 ESP (R=0.716***) (ii) The greenhouse experiment :-
1-The dry matter yield of sorghum plants was gradually and significantly reduced with increasing soil sodicity from ESP of 8.8 up to 50 .
The simple regression equations representing relationship between dry matter yield of sorghum plants and soil sodicity were as follows :
- With Zn application:
D.M. yield — Zn = 3.24 — 0.0658 ESP ( r = - 0.903***)
- With Ni application:
D.M. yield - Ni = 3.45 — 0.0630 ESP ( r = - 0.938***)
- With Pb application:
D.M. yield — Pb = 2.64 — 0.0542 ESP ( r = - 0.920***)
2- Zn- concentration in sorghum plants was gradually increased from 44.67 up to 59.00 gg /g DW as a result of increasing ESP from 20 up to 50 .
3-Ni — concentration in sorghum plants was significantly decreased with increasing soil sodicity from ESP of 8.8 up to 50%.
4-Increasing soil sodicity from ESP of 8.8 up to 50% increased Pb-concentration in sorghum plants from 6.11 up to 9.23 pg/g DW. This relationship could be summarized by the following
equation:
Pb- concentration = 5.46 +0.0721 ESP (r = 0.855***)
5-Zn-uptake by sorghum plants sharply decreased from 206.70 down to 9.44 mg/ pot with increasing soil sodicity from ESP 8.8 up to 50.
The reduction in Zn-uptake by sorghum plants as the soil sodicity
increased was described by the equations:
Zn- uptake = 170 — 3.48 ESP ( r = -0.842***)
6-Ni-uptake by sorghum plants was significantly decreased from 62.33 down to 8.43 mg/ pot as the soil sodicity increased from ESP 8.8 up to
50.
The regression equation described the relationship between soil
sodicity and Ni-uptake by sorghum plants is as follows:-
Ni — uptake = 77.4 —1.64 ESP ( r = -0.806***)
7-Pb-uptake by sorghum plants was significantly reduced from 14.79 down to 1.66 mg/ pot. The relationship between Pb-uptake by sorghum plants and soil sodicity was described by the following equation:
Pb- uptake = 16.5 — 0.318 ESP ( r = - 0.807