Evalnation of four extractants of available soil phosphorus in some Sudan soils
2005
Ali, Z.A., University of Kassala, New Halfa (Sudan) | Adam, A.I., University of Gezira, Wad Medani (Sudan) , Faculty of Agricultural Sciences
Thirteen soil samples with different physical and chemical properties were collected in 1986 from different locations in Sudan for the present study. The study included total soil phosphorus (P) and some of its inorganic fractions, available soil P and its correlations with plant P uptake. The results showed that the calcareous soils had more than 50 % of their total soil P as Ca-P, whereas, the amounts of Fe-P plus AI-P were very low, ranging from 4 to 18 mg P/kg soil. In most of the studied soils the amounts of available soil P extracted by each of the NaHCO3, distilled water and anion exchange resin were low, ranging from 1.2 to 5.7 mg P/kg soil. However, the ethylene diamine tetraacetic acid (EDTA) extracted comparatively very high amounts of P from soils with either high content of Ca-P or those which were subjected to addition of P fertilizer. A significant correlation (P 5%) was obtained between each of Ca-P, EDTA-extractable P and the P uptake by each of the test crops suggesting a probable contribution of Ca-P to plant available P in the studied calcareous soils. However, no significant correlation was found between each of the distilled water-extractable P, Fe-P plus AL-P and the P uptake of the test crops whereas NaHCO3 and anion exchange resin extractable P gave significant correlations with plant P uptake. It can be concluded from the present study that water is a poor extractant whereas EDT A is an unsuitable extractant for available soil P compared to either the NaHCO3 or the anion exchange resin. In spite of the fact that the anion exchange resin method is a more effective P-extractant from the studied soils, yet the NaHCO3 method is merited for its simplicity, time saving and is probably less expensive
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