ILs commercialization has exponentially increased in recent years because of their very different industrial utilities. Tetrafluoroborate 1-butyl-3-methylimidazolium [BMIM][BF₄] is a widely used ionic liquid in different applications. However, the number of studies about the toxic effects of [BMIM][BF₄] on the environment is very limited, especially for soils. This is striking since terrestrial ecosystems would be the first to be reached by this compound as a result of any possible accidental spill. Soil biochemical properties, and particularly the enzymatic activities, are very sensitive parameters to detect any perturbation in soil functioning. Among all the enzymes, the urease is one of the most widely used because it is highly sensitive to the presence of different exogenous agents. In this study, we carried out laboratory experiments with two soils of contrasting pH to adjust the parameters and experimental conditions of the method to determine urease activity in soils spiked with [BMIM][BF₄].