I want to study the effect of urea application on native soil urease activity. I have applied two coated urea formulation in standing kharif rice crop as basal and 1st split at 21 DAT. Remaining splits will be supplied after 45 DAT and 60 DAT respectively. So, I need to know about the exact soil sampling time which will accurately give an index of relationship between urea application and Urease activity in Gangetic alluvial soil. Please put your comment with references.
Please have a look at this link and PDF attachment.
https://www.researchgate.net/publication/226352627_Short-Term_Assay_of_Soil_Urease_Activity_Using_Colorimetric_Determination_of_Ammonium
Best of luck
Article Short-Term Assay of Soil Urease Activity Using Colorimetric ...
The urease bacteria start their activity within 12 hours and whole of conversion is complete within 3 days, provided that moisture conditions or neither two dry nor too high and there is no limiting factor like salinity, heavy metal contamination or weedicide/ insecticide effect. So you have to sample every day after application of urea until you find no urea content in it. I think, it will not take more than five days at the most.
Thank you Dr. Anil Kumar for adding good references which are relevant to the subject.
If you did this under controlled conditions you could also measure nitrite and nitrate. Do these ions influence urease acitvity?
I think after 5-7 days, when urea utilized fully. Then its effect remain in soil.
Dr. Shah! He has to monitor the changes and corelate with time so he has to sample every till 10 days or when changes stop. Dr. Paul's suggestion is good. Monitoring of NO2 and NO3 will strengthen his study further.
Colleagues, good discussion on the subject. Good background information provided by Dr.Anil kumar and good suggestion for sampling by Dr.Nazir.One initial sample may be taken immedialy after application of urea and subsequant samples after 12 hours ,24 hours ,48 hours and 72 hours.Subesquant samples can be drawn at 48 hours interval upto 9 days(8 samplings).As mentioned by colleagues the first 3 days are crucial for measurement of urease activity.The method attached by Dr.Arvind Kumar appears to be O.K.NO2 and NO3 can be measured if time and resouces permit as additional information.
Thanks to all the esteemed experts for their valuable suggestions and comments.
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