The Effect of pH on Phosphate Solubility in soilsMrak, Klara (Avtor) Wenzel, Walter W. (Mentor) Suhadolc, Marjetka (Komentor) Phosphorusphosphate solubilitysoil pHlimingfertilizerWhen proposing solutions for a more sustainable use of phosphorus (P) in agriculture, we should consider the complex interactions of biotic and abiotic factors that ultimately affect P mobility. Soil pH is a master variable of P-solubility. Published laboratory studies suggest minimum solubility of soil phosphorus (P) in the pH range, which is traditionally the target of agricultural interventions, such as lime applications. In this thesis, low and high P field-collected soils, as well P-spiked soils, were used to determine the response of P solubility to changes in pH. We changed the pH by adding base or acid to aqueous soil slurries and sodium nitrate was used as background electrolyte. In the slurries we determined P photometrically and the concentrations of P, Ca, Al and Fe and by inductively coupled plasma optical emission spectrometry (ICP-OES). We show that P solubility in low-P soils is likely controlled by desorption and, contrary to textbook information, has a solubility minimum near pH 6-7. In some high P (fertilized) soils, this pattern is likely altered by the dissolution of Ca-P minerals. In terms of methodology, we find that the colorimetrically measured P-concentration is lower, which we attribute mainly to the fact that P adsorbed on colloidal particles is not measured with this method. Further research is still needed to understand the relationship between basic soil properties, like soil pH in relation to phosphate solubility better. This will enable science to make accurate predictions and propose improved nutrient management practices to pass on to regulatory bodies, the industry and farmers.[K. Mrak]20212021-02-04 11:53:20Magistrsko delo/naloga124577UDK: 631.415.2:631.416:549.755:544.351.3(043.2)VisID: 190716COBISS_ID: 59517443sl