A review of the laboratory methods used to extract the available soil phosphorus
2005
Kisinyo, P.O.(Moi University, Department of Soil Science, Chepkoilel Campus) | Okalebo, J.R.(Moi University, Department of Soil Science, Chepkoilel Campus)
Phosphorus (P) is essential for plants root growth and energy transfer processes. It occurs in both organic and inorganic forms. It has possibly the most complicated chemistry among the major plant nutrients in terms of soil availability assessment and fertilizer application rates.Soil P determination methods, forms and' availability have been essential in developing principles and knowledge on its nature and behavior. Methods vary in principle and technical details, but the best should reflect soil P availability to plants. P determination has extraction and quantitative analysis phases. In this review extraction methods that indicate available soil P to plants are assessed. Water/dilute salt solution P represents a small portion of soil, therefore unsuitable for predicting its availability. Olsen-P test is suitable for calcareous but not neutral or acid soils. Modified Olsen-P test in addition extracts K, Zn, Cu, Fe and Mn. Mehlich-l test is suitable for soils with pH 6.0, but not calcareous, alkaline and recently phosphate rock (PR) treated soils. Bray-l test is suitable for acid soils but not calcareous and recently treated with PRo Anion exchange resin and iron oxide impregnated filter paper are suitable for acid, alkaline and calcareous, but are laborious. Suitable extraction method should be dependent on the objective, soil properties, particularly pH, equipment availability and accuracy of the results required. For routine analysis, each laboratory should be able to carry out both Olsen-P and Mehlich-1 tests to adequately address P availability in acid and alkaline soils.
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Эту запись предоставил Kenya Agricultural Research Institute