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Urease Activity in a Black Spruce Humus Sterilized by Gamma Radiation
Author(s) -
Roberge M. R.,
Knowles R.
Publication year - 1968
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1968.03615995003200040028x
Subject(s) - urease , humus , urea , chemistry , mineralization (soil science) , black spruce , ammonia , zoology , environmental chemistry , human fertilization , nitrogen , botany , agronomy , biochemistry , soil water , biology , ecology , organic chemistry , taiga
The activity of urease was studied in a black spruce ( Picea mariana (Mill.) BSP.) surface organic horizon from Baie‐Comeau, Quebec. Samples were sterilized by 60 Co radiation, incubated with urea for 8 hours at 20C and analyzed for ammonia. Urease activity decreased with an increase in humus decomposition. Field fertilization with 450 kg urea‐N/ha 2 years prior to humus sampling increased the urease activity by 40%. Laboratory preincubation of field‐fertilized and unfertilized humus with 3,500 ppm of urea‐N resulted in increased urease activity of 90%. Enzyme assays performed with 21,000 and 63,000 ppm of urea‐N gave similar relative activities to those performed with 3,500 ppm. Some mineralization of N occurred during and following irradiation in the absence of any added substrate. A direct relationship was found between enzyme activity and total and ureolytic numbers of microorganisms.