Nitrate-Nitrogen

S.D. Carroll, C.G. Herron, D.C. Lafex
University of Arkansas Soil Testing and Research Laboratory
P. O. Drawer 767
Marianna, AR 72360 USA
Phone 870-295-2851 email soiltest@uark.edu

   

Contents

Instrumentation

Extractant Solutions

Procedure

Quality Control Assessment

References

 

Extractant Solution

Stock Solution:            500PPM NO3-N

1. Dry Approximately 5 grams of KNO3 in the laboratory oven at 110ºC for 1 hour.

2. Remove dried KNO3 from the oven and place in a desiccator to cool for 2 hours.

3. Weigh 3.609 g of the dried, cooled KNO3 into a 1000 ml volumetric flask.

4. Add Reversed Osmosis (RO) water to the 1000 ml mark.

5. Add a small magnetic mixing bar and mix on a magnetic stirrer for 2 hours.

 

Extracting Solution:            0.025M  Aluminum Sulfate spiked with 5 ppm NO3-N

1. Weigh 300 g of Aluminum Sulfate into a 20 liter plastic carboy.

2. Add 180 ml of the 500 ppm NO3 stock solution.

3. Dilute to 18 Liters with RO water.

4. Add magnetic stir bar and stir on a magnetic stirrer overnight.

 

Standard Solution:             20 ppm NO3 in 0.025M Aluminum Sulfate Solution

1. Weigh 16.67 g of Aluminum Sulfate into a 1 L volumetric flask.

2. Add 40 mL of 500 ppm NO3 stock solution.

3. Dilute to the 1L mark with RO water.

4. Add a small magnetic stir bar and stir on the magnetic stirrer for 2 hours.

           

Procedure

1. Dry soil sample for 72 hours a 150ºF.

2. Crush sample in the DynaCrush soil crusher to pass a 20 mesh screen.

3. Scoop 20 g of the sample into a 31/2 oz plastic Solo Cup in the wooden sample rack.

4. Using the PeriFil pump add 42 mL of Aluminum sulfate extraction solution to the sample.

5. Vigorously stir the soil and extracting solution together using a glass stirring rod.

6. Allow sample to stand for 15 minutes.

 

Quality Control Assessment

We participate in the North American Proficiency Testing program operated by the Soil Science Society of America for all soil analyses including Nitrates.

References

Donahue, S. J. 1992. Determination of nitrate- nitrogen by specific-ion electrode. Reference Soil Media Diagnostics for the Southern Region of the United States. p 25-27. Southern Cooperative Bulletin 347. University of Georgia College of Agriculture Experiment Station. Athens, GA.

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