Partially acidulated phosphate rocks: Phosphorus release characteristics |
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Authors: | J. Hagin S. S. S. Rajan M. K. Boyes M. Upsdell |
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Affiliation: | (1) Ruakura Agricultural Centre, Private Bag, Hamilton, New Zealand;(2) Present address: Technion-Israel Institute of Technology, Haifa, Israel |
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Abstract: | Five phosphate rocks varying in formic acid P solubility from 18.9 to 52.7%, expressed as percentage of total P, were acidulated with phosphoric or sulphuric acids to 0, 20%, 33% and 50% of full acidulation and granulated. In an incubation experiment fertilizer granules of diameter 1–2 mm were mixed with two acid soils and after 1 week incubation soil samples were extracted with a 0.5 M NaOH solution. In a dissipation experiment single fertilizer granules of 4 mm diameter were implanted into soil, incubated for 1 and 4 weeks and inorganic P fractionation in the residual granules and the surrounding soil was performed. Dissipated P was greater than the water soluble P content of the partly acidulated phosphate rock fertilizers indicating the dissolution of the non-acidulated phosphate rocks. The amount of P dissipated was related to the initial water soluble P content and to the formic acid solubility of phosphate rocks used for manufacturing the fertilizers. The P dissipated increased with an increase in soil acidity. |
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Keywords: | Partially acidulated phosphate rock inorganic phosphate fractionation phosphate dissipation phosphate release |
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