Nitrogen trasformation in multy-layer soil columns tretated with an urease inhibitor

Up to date, in agriculture, the urease inhibitors had been added to the soil incorporated in fertilizers containing either urea and the inhibitors, and the inhibitor concentration was calculated as a percentage on the urea weight. The possibility to use urease inhibitor physically separated from urea-based fertilizers could afford more flexibility in its use. Particularly, the granulated inhibitors, could be utilized in soils treated with different urea based fertilizers, including livestock urine, and in an amount variable as function of soil characteristics and/or urea source (e.g mineral fertilizer, organo-mineral fertilizer or animal slurry). In this study, multi-layer soil columns were used to study the effect of an experimental granular product (RV) containing an urease inhibitor (NBPT) and a garlic extract, with the capacity to protect NBPT by oxidation, on: (a) spatial variability of soil urease activity; (b) accumulation of residual urea and mineral-N forms (NO2-, NO3-, NH4+) after urea soil addition. The results have clearly demonstrated that RV had influenced the soil urease activity along the soil columns profile and the inhibition power of RV was dependent on time and soil layer depht. RV had, furthemore, delayed urea hydrolysis and reduced the soil accumulation of ammonia and nitrite ions.