From Insoluble Minerals to Liquid Fertilizers: Magnesite as a Source of Magnesium (Mg) Nutrient

The increase in human population necessitates a tremendous growth in crop production while utilizing sustainable sources of plant nutrients. Magnesium is an important plant nutrient with high crustal abundance, but the majority (98%) is incorporated into the crystal lattice of very low solubility minerals, and thus directly unavailable to plants. Here, we present a procedure based on Mg(NO 3 ) 2 –Ca(NO 3 ) 2 –NH 4 NO 3 –H 2 O quaternary phase diagram measurements that can be used to determine the solubility and corresponding crystallization temperature ( T cryst ) of magnesium containing minerals when dissolved in HNO 3 . We use a known chemical composition, magnesite, as an example and utilize laboratory experiments with model nitrate solutions. Accordingly, chemical composition and nutrient (N, MgO, CaO) content can be obtained for aqueous solutions with T cryst of 0 °C for use as liquid fertilizers for any low solubility magnesium-containing minerals (e.g., magnesite, dolomite, talc and serpentinite), abundant in Earth’s crust but currently only sparingly used as slow release fertilizers.