A pot exrpriment was conducted in a greenhouse in Tishreen University. The
experiment included three soils differ in their chemical properties: 1) heavy clay red soil
rich in iron oxides; 2) a silty loam basiltic soil; 3) a heavet clay red soil ric
h in total
calcium carbonate (34.8 %). Treatments include application of different levels of triple
super phosphate (TSP, 46 % P2O5) ranged from 0, 20, 40, 60, 80, 100, 150, to 200 mg P/kg
soil. Pots were sowned with maize (2 plants/pot) and grown for 48 days. At harvest, plant
were hatvested before flowering by cutting shoots and extracting roots which were oven
dried and weight were recorded prior to digestion and P determination in shoot and root
tissues. Samples of rhizosphere soils from each pot replicate were taken for P fractionation
and determination.
The response of maize to P application differs at period test according to soil type.
The increase in growth was linear with increasing P level of application in theheavy red
and calcareous red soils, while was polynomial in basilitic soil. The speed of growth
increase in response to P application was influenced by native available P in the soil prior
to application. The application of P led to linear increase in resin-P and MRP fraction in
the bicarbonate extract, but not the Po fraction of the bicarbonate extract. The quantities of
fixed applied P varied according to level of P application, the ratio of P uptake by maize
plants, and chemical properties of the soil type. The proportion of applied P that was fixed
increased linerarly with increasing level of P application. It constitutes 41.7,68.5 and66%
at level of P application (20 mg/kg soil), and decreasing to30.2, 41.9 and 59.1% at level of
P application (200 mg/kg soil) for red, basiltic, and calcerous red soils, respectively.
