الفهرس 
LITERATURE OF REVIEWOnly 14 pages are availabe for public view
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Abstract
The objectives of this work wereTo investigate the status of potassium in the tested soils.
2. To use the extractions with 0.01M Oxalic acid and 0.01M CaCl2 solutions to investigate the kinetics of potassium release.
3. To compare the effectiveness of different extraction techniques for prediction of potassium supplying capacities.
To achieve these objectives, twelve Soil samples were collected from the surface
(0-30 cm) horizon of the North Western Coast of Egypt (six samples) and South AL- Gabal EL -akhdar coast of Libya (six samples).
In these soils the potassium forms and available K (using Ammonium acetate, Mehlich–3, Ammonium bicarbonate – DTPA (AB-DTPA) and Sodium chloride methods) were determined. Also, the Kinetic of soil potassium release ( using calcium chloride & oxalic acid extractants) and pot experiment ( using barely as a test crop to determine plant K uptake) were carried out. The kinetics of soil K released for each treatment was described using the following equations:
• Parabolic diffusion
• Power function
• Elovich equation
These mathematical models were tested by least square-regression analysis to determine which equation best describes the K+ release from the soils. Also the standard errors of estimate (SE) were calculated.
The most important results can be summarized as follows:
5.1 Potassium Status in Soils
• The extractants used to determine the potassium forms in the tested soils, removed different quantities of K ions from the soils.
• The different potassium forms increasingly higher in average amounts of soil K were: soluble-K (0.75 and 0.61 mg K kg-1), exchangeable-K (32.4 and 28.81 mg K kg-1), nonexchangeable-k (337.60 and 311.92 mg K kg-1), and mineral-K (4239.41 and 2516.54