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Kumar A.,National Bureau of Agriculturally Important Microorganisms | Srivastava A.K.,National Bureau of Agriculturally Important Microorganisms | Velmourougane K.,Central Institute for Cotton Research | Sidhu G.S.,Regional Center | And 9 more authors.
Proceedings of the National Academy of Sciences India Section B - Biological Sciences | Year: 2015

A study was undertaken in the established benchmark (BM) soil series in different agro-ecological sub-regions of Indo-Gangetic Plains (IGPs), India with an objective to assess the urease activity and its kinetics at different soil depths. The urease activity declined with increase in soil depth in all the selected BM soils of IGP. The mean urea hydrolysis in the surface horizon (0–30 cm; 18.2 µg NH4+/h) was 2.6-folds higher than the sub-surface horizon (121–150 cm; 7.01 µg NH4+/h). The enzyme velocity (Vmax) and enzyme efficiency (Km/Vmax) of urease hydrolysis were at par in surface and sub-surface horizons. The average Km value of urease enzyme in surface and sub-surface horizons were 4.53 and 3.96 mM, respectively. The coefficient of variation, Km for surface horizons showed higher variability and low affinity of soil urease towards substrate urea than the sub-surface horizon. Negative Pearson’s correlation coefficient was recorded between urease activity and soil depth (R = −0.86), while significant positive correlation was observed between urease activity with organic carbon (R = 0.81) and nitrogen (R = 0.81). © 2014, The National Academy of Sciences, India.

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