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Estimation of Relative Value of Phosphate Rock and Superphosphate to Plants on Different Soils
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1962
Year
EngineeringBotanySoil AmeliorationAgricultural EconomicsDifferent SoilsEarth ScienceSoil CharacterizationSoil PropertyEnvironmental ChemistryAnalytical ChemistrySoil FertilityBiogeochemistrySoil ScienceAvailability‐coefficient RatiosPhosphate RockEnvironmental EngineeringSoil ChemistryGeochemistryPrior IncubationSeed ProcessingRelative Value
Abstract The relative value of phosphate rock and superphosphate as sources of P for plants was evaluated by a test crop of sorghum on 19 soils in greenhouse cultures. The results were expressed as availability‐coefficient ratios. In the laboratory, three sets of measurements were made of P extractable from untreated soil, phosphate‐rock‐treated soil, and superphosphate‐treated soil: ( 1 ) P extracted by 0.025 N HCl, 0.03 N NH 4 F solution used in a ratio of 1 part of soil to 50 of solution by weight (method of Bray and Kurtz modified by Smith and Grava) after a 30‐day incubation period, ( 2 ) P extracted by an anion‐exchange resin without prior incubation, and ( 3 ) P extracted by an anion‐exchange resin after incubation for 30 days. Methods 2 and 3 were modifications of the method of Amer et al. The results were expressed as extractability‐coefficient ratios. The correlation between availability‐coefficient ratios and extractability‐coefficient ratios was highest with method 2 and lowest with method 1. The correlation between soil pH values and availability‐coefficient ratios was equally as close as that obtained between availability‐coefficient ratios and extractability‐coefficient ratios by method 2.