Effect of extractant pH on the release of soil phosphorus, aluminium and iron by ammonium fluoride

Authors

• Raina Niskanen University of Helsinki, Department of Agricultural Chemistry, SF-00710 Helsinki, Finland

DOI: https://doi.org/10.23986/afsci.72354

Abstract

Release of P, Al and Fe of five mineral soils in four-hour extraction by 0.1 M NH4F, pH 4.2—8.6, generally increased with decreasing pH of the extractant. Fluoride was a rather selective extractant of Al at pH 6.1—8.6 where the extractability of iron was low. NH4F, pH 4.2, released a great part of P solubilized in fractionation of inorganic soil P, and Al was extracted more than by Tamm’s acid ammonium oxalate. Acid fluoride solutions released OH- ions from soils. The initial pH of fluoride was 4.2—5.2, and it rose in the filtrates of all soils.