Exploring the Combined Effects of Different Nitrogen Sources and Chabazite Zeolite-Tuff on Nitrogen Dynamics in an Acidic Sandy-Loam Soil

Volcanic tuffs rich in chabazite zeolites have been extensively examined for their potential to enhance soil properties and increase fertilizer efficiency, both in their natural state and when enriched with nitrogen (N). However, there is a scarcity of data regarding their utilization in acidic sandy soil, particularly when used alongside organic fertilizers. This paper presents the findings of a 50-day laboratory incubation study that investigated the dynamics of N pools in an acidic sandy-loam agricultural soil treated with various N sources. These sources included urea, N-enriched chabazite zeolite tuff, and pelleted composted manure applied at a rate of 170 kg N/ha. Additionally, the N sources were tested in combination with chabazite zeolite tuff mixed into the soil to assess its role as a soil conditioner. The results revealed distinct behaviours among the tested N sources, primarily impacting soil pH and N dynamics. Soil fertilized with manure exhibited slow N mineralization, whereas N-enriched zeolite displayed a more balanced behaviour concerning net NO3−-N production and NH4+-N consumption. Both N-enriched zeolite and urea temporarily altered the soil pH, resembling a “liming” effect, while pelleted manure facilitated a prolonged shift towards neutral pH values. Considering the water adsorption capacity of zeolite minerals, caution is advised when adjusting water content and employing combustion methods to measure soil organic matter in zeolite treated soil to avoid potential inaccuracies. In summary, N-enriched chabazite zeolite tuff emerged as a valuable N source in acidic sandy-loam soil, offering a promising alternative to synthetic fertilizers and showcasing a sustainable means of N recycling.