REAGENTS

1. Diethylenetriaminepenta Acetic Acid (DTPA)
2. Triethanolamine (TEA)
3. Calcium Chloride: CaCl₂2H₂O
4. Hydrochloric Acid: HCl

EXTRACTING SOLUTION

1. 0.005 M DTPA, 0.1 M TEA, 0.01 M CaCl₂, pH 7.3
   1. Weigh 14.9 g TEA into a beaker containing 200 mL deionized water.
   2. Add 1.9668 g DTPA and mix until dissolved.
   3. In a separate beaker, dissolve 1.4699 g of calcium chloride in 100 mL deionized water.
   4. Combine the two beakers and add enough deionized water to bring the volume to 950 mL.
   5. Adjust the pH to 7.3 using hydrochloric acid.
   6. Transfer to a 1 liter volumetric flask. Dilute to volume with deionized water and mix well.

EXTRACTING PROCEDURE

1. Weigh 10 g soil into a 50 mL extraction bottle.
2. Add 20 mL. DTPA extracting solution.
3. Shake for 2 hours on a shaker box at 180 oscillations per minute.
4. Filter using Whatman #42 paper.
5. Analyze by either Atomic Absorption or Inductively Couples Plasma instrumentation.

CALCULATION

ppm element in extract × 2 = ppm element in soil

REFERENCE

1. Lindsey, W. L., and W. A. Norvell. 1978. Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil Sci. Soc. Amer. J. 42:421-428.