REAGENTS

Acetic Acid: CH3COOH
Ammonium Nitrate: NH4NO3
Ammonium Fluoride: NH4F
Nitric Acid: HNO3
Ethylenediaminetetraacetic Acid: EDTA

EXTRACTING SOLUTION

  1. 0.2 N CH3COOH, 0.25 N NH4NO3, 0.015 N NH4F, 0.013 N HNO3, 0.001M EDTA.
    1. Weigh 20 g NH4NO3 into a 1 liter volumetric flask containing 800 mL deionized water.
    2. Add 0.5556 g NH4F and dissolve.
    3. Add 0.2922 g EDTA and dissolve.
    4. Add 11.5 mL acetic acid and 0.82 mL nitric acid.
    5. Dilute to volume with deionized water and mix well.

EXTRACTING PROCEDURE

  1. Scoop 2.5 mL soil into a 50 mL extraction bottle.
  2. Add 25 mL. Mehlich III extracting solution.
  3. Shake for 5 minutes on a reciprocating shaker at high speed (250 oscillations per minute).
  4. Filter using Whatman #1 paper.
  5. The filtrate may be analyzed for all elements by inductively coupled plasma. Atomic Absorption may be used for all elements except P. If Atomic Absorption methods are used, P will have to be analyzed separately by a colorimetric procedure.

CALCULATION

ppm element in extract × 10 = mg element/dm3 in the soil.

REFERENCES

  1. Mehlich, A. 1978. New extractant for soil test evaluation of phosphorus, potassium, magnesium, calcium, sodium, manganese, and zinc. Commun. Soil Sci. Plant Anal. 9(6):477-492.
  2. Mehlich, A. 1984. Mehlich 3 soil test extractant: a modification of Mehlich 2 extractant. Commu. Soil. Sci. Plnat Anal. 15(12):1409-1416.