Calcium Solubility In Zeolite Synthetic-Apatite Mixtures

Life support systems at a lunar or martian outpost will require the ability to produce food growing in 1) treated lunar or martian regolith; 2) a synthetic soil, or 3) some combination of both. Zeoponic soil, composed of NH4 (-) and K-exchanged clinoptilolite (Cp) and synthetic apatite (Ap), can provide slow-release fertilization via dissolution and ion-exchange. Equilibrium studies indicate that KNH4, P, and Mg are available to plants at sufficient levels, however, Ca is deficient. Ca availability can be increased by adding a second Ca-bearing mineral: calcite (Cal); dolomite (Dol); or wollastonite (Wol). Additions of Cal, Dol, and Wol systematically change the concentrations of Ca and P in solution. Cal has the greatest effect, Dol the least, and Wol is intermediate.