Assay of urease activity in soils

Yahya Mohd Nor

Abstract

A method for assay of urease activity is described. It involved aerobic incubation of a 10-g sample of soil at 37^oC for 6 hours after addition of urea substrate to it, and colorimetric determination of the urea remaining after extraction with 2.5M KCI containing Ag₂ SO₄ (100 ug/ml) as urease inhibitor. The effect of extractant on the colour of the complex and recoveries of urea added to soils by the method were also evaluated. The urease activity in 14 Malaysian soils studied indicated that the soils have varying capacity to hydrolyzed urea. Soil pH and urease activity correlated well, but neither organic carbon content nor cation exchange capacity bore any significant relationship.

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