Influence of natural zeolite on nitrogen dynamics in soil

Abstract

Sorption of the cations NH_4^+, Al^{3+}, Fe^{2+}, Mn^{2+}, and Mg^{2+} in powdered zeolite and its mixture with soil was monitored. More than 90% of the observed cations were fixed in the zeolite in the first few minutes of the laboratory experiment, which is a very fast speed of sorption, and the ammonia cations reacted fastest. Consequently, the dynamics of the nitrate and ammoniac nitrogen in soil after application of zeolite in different amounts was monitored. A decreased ammonium content was apparent in the variants with zeolite 1 month after zeolite application in comparison with variants without zeolite owing to the specific fixation of NH_4^+ cations in the zeolite lattice (92.5 mg in the control variant and 77.2-81.0 mg per kg of soil in the tested variants). Three months later, there was an increase in ammonium content in the variants with zeolite of 24% to 59% in comparison with the control variant owing to gradual ammonium release from the zeolite lattice. Six months after the zeolite application, statistically significant differences were found not only between the control variant and the variants with zeolite, but also between individual variants with various zeolite doses (H = 14.201; P = 0.003 according to the Kruskal-Wallis test). The nitrification process in the soil was less intense under the influence of applied zeolite. The nitrate nitrogen contents in the soil decreased by 66% to 78% in comparison with the control variant in the autumn period; therefore, the amount of nitrate leaching from the soil horizons to the groundwater was less. In summary, zeolite can be considered to be a slow-releasing nitrogen fertiliser.