Mahboubeh Eslami - Ferdowsi University of Mashhad, Faculty of Agriculture, Department of Soil Science, Mashhad, Iran
Reza Khorassani - Ferdowsi University of Mashhad, Faculty of Agriculture, Department of Soil Science, Mashhad, Iran
Amir Fotovat - Ferdowsi University of Mashhad, Faculty of Agriculture, Department of Soil Science, Mashhad, Iran
Akram Halajnia - Ferdowsi University of Mashhad, Faculty of Agriculture, Department of Soil Science, Mashhad, Iran

Clinoptilolite is an abundant and inexpensive natural zeolite with unique chemical features for adsorption of monovalents such as K+ which makes it a suitable candidate for production of slow release fertilizers1. Zeolites can be applied to soil both in natural and pre-charged forms. Pre-charging zeolite with nutrients can be done by soaking themin chemical solutions, swine liquids, or melted fertilizers 2,3,4. The adsorption and desorption (ion exchange) properties of the zeolites is highly influenced by their crystal chemistry and geochemical behaviour of the adsorbate5. Preparation of K+-enriched zeolite through soaking method, investigation of the mechanism of saturation, and finally evaluation of this newly prepared K source as a slow release fertilizer via column experiment are the main objectives of this reserach.