Are you extracting a representative subsample using a KCl solution?

thank you very much dear Paul Milham for the reply

Yes I have used the KCL for the extraction

I followed the company's instructions for ammonium and nitrate but I still got different results every time I do.

Do you think this result can be published

Let's go back to first principles:

1. What concentrations are you measuring and how well do they fall within the claimed measurement range?

2. Do you make different standard solutions to calibrate the instrument on the different occasions?

3. Do you make up different batches of KCl and measure the reagent blank?

You must measure the extracts fresh

You might contact the manufacturer and ask if they know what the problem is. Perhaps the manufactured batch has a problem.

No I don't think it likely that these observations are publishable.

Again I appreciate your concern Sir

Regarding your questions

1. What concentrations are you measuring and how well do they fall within the claimed measurement range?

For both ammonium and Nitrate, I use 2 measure range

Ammonium measure range 20-180 mg/l NH4 and 0.2-7.0 mg/l NH4

Nitrate measure range 3-90 mg/l NO3and 5-225 mg/l NO3 g

2. Do you make different standard solutions to calibrate the instrument on different occasions?

I did just the initial calibration without solutions just the blank strip

3. Do you make up different batches of KCl and measure the reagent blank?

You must measure the extracts fresh

I am sorry I mistake in the first answer I only used 0.01 M CaCl2 and I did use the fresh sample extract

You might contact the manufacturer and ask if they know what the problem is. Perhaps the manufactured batch has a problem.

I haven’t tried to contact the manufacturer because I wanted the contact with soil expert because my knowledge of soil is very limited