Bicarbonate Phosphorus Extraction Inorganic & Organic

By Jared L. DeForest

Reagents

0.5M NaHCOV₃ (enough for 50 samples)

In 2 l volumetric flask

• 84 g Sodium Bicarbonate
• Adjust pH to 8.5.
• Bring to volume with DI water Keep refrigerated for a month.

Procedure - Total bicarb P

Soil solution extraction (1:20 dilution)

In a 50 ml Oakridge centrifuge tube

• 2 g Oven-dried equivalent field fresh, sieved soil
• 40 ml 0.5M NaHCO₃
• Shake for 18 hours on an angle Centrifuge @ 2500 rpm for 5 minutes.
• Decant into 15 ml centrifuge tube.
• Analyzing for P on ICP-OES for total bicarb P

Procedure - Inorganic bicarb P

In a 15 ml centrifuge tube

• 5 ml Solution (draw off before analyzing for total bicarb P)
• Slowly add 2.5 M H₂SO₄ (expect effervescences) to neutralize the solution. Record the amount added to determine dilution. Test with pH paper.
• Vortex after ~2 minutes to de-gas the sample.
• If necessary, centrifuge @ 2500 rpm for 5 minutes.
• Analyze for inorganic P using the ascorbic acid method.
• Organic bicarb P = Total bicarb P - Inorganic bicarb P

Created: 12/17/08 Revised: 10/10/11