20.500.12556/RUL-124577 The Effect of pH on Phosphate Solubility in soils Vpliv pH na topnost fosfata v tleh When 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. Pri predlogih ukrepov za bolj trajnostno uporabo fosforja (P) v kmetijstvu, je potrebno upoštevati zapletene interakcije biotskih in abiotskih dejavnikov, ki vplivajo na dinamiko P v tleh. Vrednost pH tal je glavna kontrolna spremenljivka topnosti P. Objavljene laboratorijske študije pokažejo minimalno topnost fosforja v tleh v območju pH, ki je tradicionalno tarča kmetijskih posegov, kot je apnjenje. V magistrski nalogi smo v vzorcih tal iz poljskih poskusov z majhnimi in velikimi vsebnostmi P, ter v tleh z dodanim P, določali odziv topnosti P na spremembo pH v suspenziji tal z dodajanjem kisline oz. baze. Kot osnovni elektrolit smo uporabili natrijev nitrat. V suspenzijah smo fotometrično določili vsebnost P in z atomsko emisijsko spektroskopijo z induktivno sklopljeno plazmo vsebnosti P, Ca, Al in Fe. Pokazali smo, da je topnost P v tleh z majhno vsebnostjo P verjetno nadzorovana z desorpcijo, in dosega, v nasprotju s pogostimi navedbami, najmanjše vrednosti okrog pH 6-7. V nekaterih s P bogatih tleh (gnojenih) je vzorec topnosti spremenjen, verjetno zaradi raztapljanja Ca-P mineralov. V metodološkem smislu ugotavljamo, da je kolorimetrično izmerjena koncentracija P manjša, kar pripisujemo predvsem dejstvu, da s to metodo hkrati s preostalim P ne izmerimo P, ki je adsorptivno vezan na koloidne delce. Za razumevanje razmerja med osnovnimi lastnostmi tal, kot je pH tal v odnosu s topnostjo fosfatov, so potrebne nadaljnje raziskave, ki bodo znanosti omogočile natančnejše napovedi o agroekologiji fosfata. Tovrstna dognanja so potrebna za izboljšano prakso upravljanja s hranili, prenesti pa se morajo iz znanosti na regulativne organe, industrijo in kmete. Phosphorus phosphate solubility soil pH liming fertilizer Fosfor topnost fosfata pH tal apnjenje gnojenje true false false [K. Mrak] Angleški jezik Slovenski jezik Magistrsko delo/naloga 2021-02-04 11:53:20 2021-02-04 11:53:27 2022-09-04 04:00:17 0000-00-00 00:00:00 2021 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 631.415.2:631.416:549.755:544.351.3(043.2) 190716 59517443 11850.pdf 11850.pdf 1 C75D3C7E1FBD02AC1911F3A6F95BD5F3 760dc6a02c8e0b18bc976e975c69e859c0ff7075108713871e99118962fb2db6 96cbdef9-a1bb-11eb-a523-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=140114 Biotehniška fakulteta 0 0 0