The Relation Between Available and Extractable Phosphorus in Some Soils of the Central Clay Plain of the Sudan.

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Salah EL Din Mohamed Ali Abboud, Abboud
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University of Khartoum
A considerable volume of literature has been published on different aspects of soil phosphorus particularly on the assessment of phosphorus availability. The work described in this thesis is one of the first attempts in the Sudan to investigate the relation between available and extractable soil phosphorus. Soil phosphorus was fractionated and extracted with different chemical and biological procedures. The amounts of soil phosphorus extracted were correlated with actual crop uptake. A glasshouse pot experiment was designed to check the crop response to added phosphorus fertilizer. The soil investigated generally did not show response to added phosphorus fertilizer. Calcium bound phosphate was the dominant fraction of soil phosphates. This fraction gave a significant positive correlation co-efficient with crop uptake (r= 0.6805). The conventional methods extracted variable amounts of soil phosphorus. A modification was introduced into the Neubauer seedling test. Although this work did not cover all the aspects of phosphorus availability in these soils, yet it revealed the need for more studies on plant soil phosphorus relations.
Extractable Phosphorus;Soils; Central Clay Plain;Sudan.