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Michaelis Constant of Soil Urease¹

ABSTRACT

Application of the Michaelis-Menten equation to urease activity of soil showed that the Michaelis constant (K_m) changed with fluctuation in microbial population and thus with changes in the proportion of microbial and adsorbed urease. Regression of urease activity on number of ureolytic microorganisms permitted division of total urease activity into portions caused by microbial and adsorbed forms, respectively. Computations using the partitioned urease activities gave K_m's for the microbial and adsorbed forms of 0.057 and 0.252M, respectively. These values are similar in order of magnitude to those reported in the literature and thus further support the hypothesis that urease is active in both microbial and adsorbed forms in soil.

¹ Contribution from the Dept. of Agronomy, Univ. of Ill. Urbana-Champaign.

² Instructor and Professor of Soil Fertility, respectively, Univ. of Ill., Urbana-Champaign. Senior author is now Assistant Olericulturist, Dept. of Vegetable Crops, Univ. of Calif., Davis.

Received for publication June 24, 1969. Accepted for publication September 2, 1969.