Effect of fractionation on location of enzyme activities in soil structural units

Summary Two different soils were fractionated with three granulometric procedures. Enzyme activity measurements were carried out in four fractions of real (undisturbed), stable (water-dispersed) and structural (water-dispersed and physically disrupted) soil units.A predominance of catalase (67.3%), dehydrogenase (57.6%) and urease (65.3%) activities was observed in soil structural microunits with diameters of less than 50 m. Highest protease activity was found in fractions with a diameter of less than 50 m (66.3%) and in fractions with a diameter ranging from 200 to 2000 m (18.5%) which contain organic matter of a higher and lower grade of humification, respectively.All fractionation procedures result in a loss of total enzyme activities, which was more clear in the physically disrupted soil than in the sieved soil (e.g. 38.4% vs. 5.9% loss of urease activity).