Abstract: Natural zeolites with favourable properties of ion exchange and adsorption have received increasing attention in agriculture application. But negative effects may be obtained of applying them without considering their special characters. Our experiments indicate that the cationic form of natural zeolites with higher content exchangeable Na⁺ could greatly influence the growth of crops after their interaction with soil and fertilizer. For this reason, the agricultural suitability of natural zeolites should be re-evaluated.

Key words: Natural zeolite, Cationic form, Agricultural suitability