Phosphorus status of some Ethiopian soils, II. Forms and distribution of inorganic phosphates and their relation to available phosphorus.
1991
Mamo T. | Hague I.
The P status of 32 surface soils from various locations of Ethiopia was studied. Total P content of the soils ranged 185-1981 ppm. The relative abundance of the various inorganic P fractions was in the order of calcium-P (Ca-P) > reductant-P (red-P) >iron-P (Fe-P) > aluminum-P (Al-P). Organic P on the average constituted about 41 % of the mean total P content of the soils. Multiple correlation analysis of the data showed that various P fractions were significantly correlated with total P in the soils. Available P in the soils was estimated by eight chemical methods. The lowest mean P value was obtained with the Bray I method and the highest was found with Truog's method. The P values extracted by all methods, except for the Bray I method, were significantly correlated with Al-P, and P extracted by the Olsen and Dabin methods were also correlated with Fe-P as well as with Al-P. P estimated by Truog, Bray II, Waren and Cooke, Williams and Stewart, and Egner methods were also significantly correlated with Ca-P. None of the P fractions correlated with P values extracted by the Bray I method. Stepwise regression analysis of the data found that Al-P was the major source of differences between Olsen, Dabin, Egner and Bray I methods and Ca-P fraction was the major source in Truog, Warren and Cooke, William and Stewart, and Bray II methods.
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