I am investigating the ability of certain substances to inhibit the activity of the urease enzyme in soil, so as to reduce the hydrolysis of urea applied as a fertilizer. I am looking for a "fast" lab method (in terms of hours or at most days) that will allow me to quantify urease enzyme activity.
To date, I have followed the method of E. Kandeler and H. Gerber (1988): Short-term assay of soil urease activity using colorimetric determination of ammonium https://www.researchgate.net/publication/226352627_Short-Term_Assay_of_Soil_Urease_Activity_Using_Colorimetric_Determination_of_Ammonium .
To evaluate the efficacy of the method, I used an established urease inhibitor Nexur® a N fertilizer with urease inhibitor NBPT (0.04% N-butyl phosphoric triamide (NBPT) and N-propyl phosphoric triamide (NPPT) mixture) as a positive control.
The problem is that the samples treated with the inhibitor give me the same ammonia production as the samples without.
Do you know of another valid method and an effective urease activity inhibitor?
Thank you for your time
@ Elena, You may try with May and Douglas (1976) method where they uses a phosphate buffer (pH 8.8) and a urea substrate concentration of 0.007 M. Incubation for 4 h at 37°C is recommended and urease activity is estimated by determining the amount of ammonium produced by urea hydrolysis in soil. The method is precise, and compares favourably with other procedures.
Tabatabai, M. A., & Bremner, J. M. (1972). Assay of urease activity in soils. Soil Biology and biochemistry, 4(4), 479-487.
Though relatively old method but quite fast. The ammonium-N released is determined using steam distillation.
Yes, I agree with .Siddhartha Kaushal
Tabatabai, M. A., & Bremner, J. M. (1972). Assay of urease activity in soils. Soil Biology and biochemistry, 4(4), 479-487.
This protocol is convenient, quick.
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