In the framework of the project of ammonia removal from waste gases, its adsorption on a natural zeolite, clinoptilolite, was investigated. The material can be simply modified to reach an adsorption capacity comparable with commercial adsorbents for removal of ammonia from the gas phase. The adsorbed ammonia can be utilized as a nitrogen source in plant cultivation. On admixing the ammonia-saturated adsorbent with soil, the yields and quality of plant production were favourably influenced, also by the presence of other nutrients in the adsorbent (K, Ca). The modification of clinoptilolite before ammonia adsorption influences the bonding of ammonia to the adsorbent and, consequently, also the dynamics of its release into soil (soil solutions).