Apatite–Biotite–Carbonatite (Stjernøy, N-Norway): Potential and Obstacles Regarding a Multinutrient Rock-Fertilizer

Abstract

Apatite–biotite–carbonatite (ABC) from the Lillebukt alkaline complex (N-Norway) contains 42 wt% calcite, 30% biotite, and 7.5% apatite. Agrochemically, it is lime with a K, P, and Mg nutrient potential. Previous K-fertilizing trials with ABC rock-powder have provided good results, and renewed experiments have started to examine the overall effect of ABC rock-powder on soil and plants. The underlying problems with ABC rock-fertilizer are (i) Potential ecotoxicity of high barium and strontium of up to 15 g/kg, substituting K in biotite and Ca in calcite, respectively. An in situ soil and vegetation study on Stjernøy has shown that Ba-content in plants is related to plant species and Ca in plant. Highest Ba-concentration showed the nitrogen-fixing legume Vicia cracca L., lowest grasses. Strontium follows mainly Ca-content in plants. (ii) Low plant availability of P from magmatic apatite at high pH, when applying whole-rock powder. (iii) To find adequate dry mineral separation methods, in particular, to separate calcite and apatite, with the aim to increase nutrient concentration in possible fertilizer products. Vegetation study, plant and soil experiments, and mineral separation tests will hopefully give a decision base for application of ABC as rock-fertilizer.