Downy jasmines [Jasminum multiflorum (Burm. f.) Andr.] and areca palms [Dypsis lutescens (H. Wendl.) Beentje & J. Dransf.] were grown in containers filled with a fine sand soil (SS) or with a pine bark-based potting substrate (PS). Each of these substrates was amended with 0%, 10%, or 20% clinoptilolitic zeolite (CZ) by volume. Plants were fertilized monthly with a water-nonsoluble 20N-4.3P-16.6K granular fertilizer. Downy jasmines were larger and had darker color in CZ-amended PS and were larger in CZ-amended SS than in nonamended SS or PS. Areca palms, which tend to be limited by K in SS had better color and larger size when the SS was amended with CZ. In PS, where K is seldom limiting, areca palms did not respond to CZ amendment of the PS. Both ammonium (NH4)-N and potassium (K) were retained against leaching by CZ, but some of the NH4-N adsorbed to CZ was subject to nitrification, either before or after its release into the soil solution. Some phosphate (PO4)-P was also retained by CZ.
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