الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Interactions occur between the micronutrients as well as with
macronutrients, these interactions may take place in the soil or within the
plant. Since these interactions modify the nutrition of plants, they must be
understood and considered in providing an adequate supply of micro and
macronutrients.
This investigation was conducted to study: (1) the effect ofP and Zn
application on the dry matter yield, concentration and uptake of P, Zn and Fe
by soybean plants grown on alluvialand calcareous soils, (2) the effect of Zn
source, where Zn was applied as ZnS04.7H20 or Zn-EDTA on the above
mentioned parameters, (3) the influence of P and Fe application on the dry
matter yield and the contents of P, Zn and Fe in soybean plants grown on
alluvial and calcareous soils, (4) the effect of Fe source, when Fe was added
as FeS04·7H20 or Fe-EDDHA on the above mentioned parameters, (5) the
effect of P rate and incubationtime in presence of Zn as ZnS04.7H20 (at a
constant rate of 20 mg Zn kg-I soil) on the availability of soil P, Zn and Fe in
the alluvial and calcareous soils, and (6) the effect ofP rate and incubation
time in presence of Fe as FeS04.7H20 (at a constant rate of20 mg Fe kg-I
soil) on the availability of soil P, Fe and Zn in the alluvial and calcareous
soils.
To achieve the first four objectives, two greenhouse experiments were
conducted:
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1- Greenhouse experiment to study P and Zn interaction:
Phosphorus was added as mono-calcium dihydrogen phosphate
(CaH2P04) at 50, 100 and 150 mg kg-I soil to the alluvial and calcareous
soils packed into plastic pots. Zinc was applied at three rates namely; 5, 10
and 20 mg kg-I soil as ZnS04.7H20 or Zn-EDTA. Soybean seeds were
seeded, then thinned to three plants pot-! soil. After 45 days, plants were
harvested and their contents of P, Zn and Fe were determined. The results
obtained from this experiment can be briefly summarized as follows:
(1) Dry matter yield of soybean plants grown on the alluvial and calcareous
soils increased significantly with increasing P from 50 to 100 mg kg-I soil
and increased slightly with increasing P from 100 to 150 mg kg-I soil.
However, in the calcareous soil, increasing P from 100 to 150 mg kg-I
soil resulted in a slight decrease in dry matter yield.
(2) The dry matter yield of soybean grown on both soils increased with
increasing Zn rate from 5 to 10 mg kg-I soil and decreased when Zn was
applied at 20 mg kg-I soil. The most effective Zn rate was 10 mg kg-I
soil.
(3) In the alluvial soil, the mineral form of Zn was the superior source, but
under the calcareous soil it was the inferior one.
(4) Increasing the applied rate ofP increased significantly the concentration
of P in the plants grown on the alluvial and calcareous soils at all levels of
applied Zn. The application of mineral Zn resulted in an increase in P
concentration in plants compared with the chelated Zn,
(5) Phosphorus uptake by plants increased with increasing the application rate
of P. The chelated Zn increased significantly the uptake ofP particularly
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when phosphorus was added at 150 mg P kg- I soil to the alluvial soil.
However, in the calcareous soil, there was no significant differences
between the two sources.
(6) The concentration of Zn in plants decreased significantly with increasing P
rate. Also, the concentration of Zn increased significantly with increasing
Zn rate especially when it was applied with the first rate of P (50 mg P
kg-I soil).
(7) The effect of Zn source on Zn concentration was more pronounced when
it was applied to the calcareous soil and the chelated form was the
supenor one.
(8) Zinc uptake was increased with increasing P rate up to 100 mg P kg- I soil
and then decreased with increasing P rate to 150 mg P kg- I soil. Zinc
uptake was affected positively with increasing Zn rate when Zn was
applied either as mineral or chelated form. This trend was similar in both
soils.
(9) The chelated Zn was more efficient in increasing Zn uptake by plants than
the mineral one in both soils.
(10) Iron concentration and uptake by plants grown on the alluvial and
calcareous soils was decreased with increasing P and Zn rates. Plants
receiving chelated form ofZn showed relatively higher value of Fe uptake
than the mineral form.