The release of ammonium-ions from the ammonium-enriched zeolites in the soil system

The effect of NH4+-enriched zeolites as a source of slow released ammonium nitrogen in the soil system was tested in the pot experiments. The natural clinoptilolite (Eastern Slovakia) and the synthetic zeolite P-c prepared by hydrothermal alteration from the power station ashes were used. The NH4+-enriched zeolites (54 mg NH4+-N.g(-1) synthetic zeolite P-c and 12 mg NH4+-N.g(-1) natural clinoptilolite) were mixed with the soil (orthic Luvisol of the Praha-Ruzyne: location) to achieve the nitrogen content of 300 mg NH4+-N.kg(-1) dry soil. The comparative experimental set with the addition of the crystalline ammonium sulphate into the soil and the control set without the fertilizer addition were also observed. The samples of the soil solution from pots were sampled and NH4+, NO3-, K+, Na+, Ca2+ and Mg2+ concentrations were determined. The relatively rapid release of NH4+ ions occurred with respect to the ion-exchange reactions between the zeolites and soil solution. After the first five to seven days the relatively high concentrations of ammonium nitrogen in the soil solution (40 to 70 mg NH4+-N.l(-1)) decreased rapidly owing to the nitrification processes and after 20 to 25 days the NH4+ ions were not determined in the soil solution. The same trend both in the experimental sets with NH4+-enriched zeolites addition and in the one with ammonium sulphate addition was observed.