ChileanJAR

In this work urease activity in several volcanic ash derived soils is determined. Ammonium released, after incubation of soil samples with buffered urea solution, was estimated by using the indophenol blue colorimetric method. The eftect of soil pH, organic matter content, microbial population and ureolytic microflora on urease activity was studied. No clear relationship was observed between urease activity and soil pH or ureolytic microorganisms. The results show that urease activity is positively correlated with organic matter content. This suggests that enzymatic activity in these ando- sois is supported basically by enzymes which are accumulated and stabilized by interactions with soil active surfaces, speciaiiy organic ones. The experiment showed an important effect of wheat on the enzymatic activity.